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D D Thompson

Publications and source records attributed to D D Thompson.

At least 37 records · Page 2Linked to original sources
PubMed1998

Estrogen-induced genes in the uterus of ovariectomized rats and their regulation by droloxifene and tamoxifen.

The identification and characterization of estrogen regulated genes in reproductive tissues is an important step in understanding estrogen's mechanism of action in sexual development and neoplasia. It is also important, given the clinical interest, to evaluate the molecular effects of estrogen agonists/antagonists such as tamoxifen and droloxifene in reproductive tissues. In this report, our goal was to identify estrogen regulated genes in the uterus and to compare the regulation by estrogen and tamoxifen with that of droloxifene. A subtractive cDNA library strategy was developed to identify estrogen-regulated genes in the uteri of ovariectomized rats 4 h after treatment with 17-alpha-ethynyl estradiol (30 microg/kg). The mRNAs encoding 8 genes were confirmed by Northern blot analysis to be induced at early times following estrogen administration. Calcium binding protein 9 kDa and complement protein 3 are well characterized estrogen regulated genes that were identified in the library and served as markers for estrogen action. In addition, mRNAs encoding the interleukin 4 receptor, heat-shock protein 70 kDa, metallothionein, tumor necrosis factor regulated gene 6, inositol-1-monophosphate synthase, and cyr-61 were induced in the uterus by estrogen. The identified mRNAs were then examined for regulation by droloxifene (1 and 10 mg/kg, p.o.) and tamoxifen (10 mg/kg, p.o.). Both droloxifene and tamoxifen induced mRNA levels for all of these genes. However, clear quantitative and temporal differences were observed when comparing estrogen versus droloxifene versus tamoxifen. For example, estrogen induced IL4 receptor mRNA to a greater degree than did tamoxifen or droloxifene. Conversely, tamoxifen resulted in a much greater induction of cyr61 than did either estrogen or droloxifene. Droloxifene at 1 mg/kg, an efficacious dose for prevention of bone loss in this model, did not or only slightly induced the mRNA for all of the genes examined with the exception of cyr61. In conclusion, the modified subtractive library method used in this study proved to be efficient in the identification of estrogen-regulated genes in the uterus. The identities of the regulated genes were consistent with the concept that estrogen functions to prime uterine tissue for increased responsivity to extracellular signals such as growth factors and cytokines. Elucidating the physiological role of these newly identified estrogen responsive genes and the mechanisms responsible for the different responses to droloxifene versus estrogen and tamoxifen may be important in enhancing our understanding of tissue selective estrogen agonists/antagonists.

Animals↗
PubMed1998

Prostaglandin E2 increases bone strength in intact rats and in ovariectomized rats with established osteopenia.

It is well documented that prostaglandin E2 (PGE2) has the ability to stimulate bone formation, improve bone structure, and increase bone mass in intact or osteopenic rat models. However, the effects of PGE2 on the mechanical properties of bone have not been investigated previously. The purpose of our study was to determine the effects of PGE2 on the mechanical strength of bones in rapidly growing, adult, and ovariectomized rat models. In study I, PGE2 at 3 mg/kg per day, or vehicle, was given by daily subcutaneous injections for 30 days to rapidly growing (3-month-old) intact male rats. Compared with controls, PGE2 significantly increased initial maximal load and stiffness of cancellous bone at the distal femoral metaphysis (DFM) as determined by an indentation test. As determined by a compression test, rats treated with PGE2 showed a significant increase in maximal load, and a nonsignificant increase in stiffness in the fifth lumbar vertebral body (L5) when compared with controls. In study II, PGE2 at 3 mg/kg per day, or vehicle, was given by daily subcutaneous injection for 30 days to mature (10-month-old) intact male rats. PGE2 treatment significantly increased initial maximal load and stiffness of the DFM and L5. PGE2 induced a significant increase in maximal load, but not stiffness, in the femoral neck (FN), as determined by a cantilever compression test. There was an increase in maximal load in a three-point bending test at the femoral shaft (FS) although the increase did not achieve statistical significance. No change in stiffness in the FS was found after PGE2 treatment. In study III, 3-month-old female rats were sham-operated or ovariectomized (ovx) for 30 days. Thereafter, PGE, at 1 or 3 mg/kg, or vehicle, were given by daily subcutaneous injection to these rats for 30 days. After 30 and 60 days, ovx induced a significant decrease in initial maximal load and stiffness of cancellous bone at the DFM as compared with sham controls. In ovx rats with established osteopenia, PGE2 at 1 mg/kg per day nonsignificantly increased the initial maximal load and stiffness, whereas, at 3 mg/kg per day, PGE2 completely restored the initial maximal load and stiffness of DFM to sham control levels. Similarly, maximal load and stiffness of L5 decreased significantly in ovx rats compared with sham controls at 30 days postsurgery. PGE2 at 1 mg/kg per day partially restored the maximal load, whereas, at 3 mg/kg per day, it completely restored the maximal load and stiffness of L5 in the established osteopenia, ovx rats. At the FS, PGE2 at 3 mg/kg per day nonsignificantly increased maximal load (+11%) and significantly increased stiffness (+25%) compared with ovx controls. Neither ovx nor PGE2 treatment caused a significant change in the maximal load and stiffness of the FN in this study. These results reveal that PGE2 significantly increased the mechanical strength at various skeletal sites in rapidly growing and mature male rats, although the increase in femoral shafts was not statistically different. Furthermore, PGE2 completely restored mechanical strength to the cancellous bone in ovx rats with established osteopenia.

Animals↗
PubMed1998

Is malnutrition overdiagnosed in older hospitalized patients? Association between the soluble interleukin-2 receptor and serum markers of malnutrition.

BACKGROUND: Many researchers have speculated that markers of malnutrition such as albumin, prealbumin, cholesterol, and transferrin are influenced by inflammation. The mechanism of this interaction has not been well understood. METHODS: This was a prospective cross-sectional study. We evaluated 72 male patients older than 60 years admitted to a geriatric rehabilitation unit. Subjects with severe hepatic or renal diseases were excluded. We measured body mass index, caloric intake, serum albumin, prealbumin, cholesterol, transferrin, hemoglobin, and total lymphocyte count. To detect inflammation, we measured C-reactive protein, Westergren sedimentation rate, fibrinogen, and cytokines including tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), IL-6, IL-2, and the soluble IL-2 receptor. RESULTS: Soluble IL-2 receptor was negatively associated with albumin (r = -.479, p < .0001), prealbumin (r = -.520, p = < .0001), cholesterol (r = -.487, p = .0001), transferrin (r = -.455, p = .0002), and hemoglobin (r = -.371, p = .002). TNF-alpha, IL-1 beta, IL-6, and IL-2 were not associated with these measures. CONCLUSIONS: Inflammation increases the incidence of hypoalbuminemia and hypocholesterolemia, potentially leading to overdiagnosis of malnutrition. We suggest that albumin, cholesterol, prealbumin, and transferrin be used with caution when assessing the nutritional status of older hospitalized patients. In the future, soluble IL-2 receptor levels might be used to correct for the impact of inflammation on these markers of malnutrition.

Aged↗
PubMed1998

Effects of CP-336,156, a new, nonsteroidal estrogen agonist/antagonist, on bone, serum cholesterol, uterus and body composition in rat models.

We have discovered a new, nonsteroidal, potent estrogen agonist/antagonist, CP-336,156. CP-336,156 binds selectively and with high affinity to the human estrogen receptor-alpha with a half-inhibition concentration of 1.5 nM, which is similar to that seen with estradiol (4.8 nM). When given orally to immature (3-week-old) female Sprague-Dawley rats for 3 days at doses of 0.1, 1.0, 10, or 100 microg/kg x day, unlike 17alpha-ethynyl estradiol, CP-336,156 had no effect on uterine wet or dry weight. Similarly, no uterine hypertrophy was observed in aged (17-month-old) female rats treated (p.o.) with CP-336,156 at 10 or 100 microg/kg x day for 28 days. We also found that CP-336,156 decreased total serum cholesterol and fat body mass and had no effect on lean body mass in these aged female rats. In 5-month-old ovariectomized (OVX) Sprague-Dawley female rats, CP-336,156 completely prevented OVX-induced increases in body weight gain, total serum cholesterol, and serum osteocalcin at doses between 10 and 1000 microg/kg x day after 4 weeks. At these doses, CP-336,156 completely prevented OVX-induced bone loss and inhibited the increased bone turnover associated with estrogen deficiency in lumbar vertebrae, proximal tibiae, and distal femora. Similar to estrogen, CP-336,156 induced apoptosis and p53 expression with a concomitant decrease in the number of tartrate-resistant acid phosphatase-positive multinuclear cells in rat bone marrow cell cultures in vitro, suggesting that the induction of apoptosis may be a mechanism for the estrogenic activities of CP-336,156 in bone. In summary, CP-336,156 is a new, orally active, nonsteroidal, potent estrogen agonist/antagonist that has similar effects in bone as estradiol but without the uterine-stimulating effects associated with estradiol in rats.

Adipose Tissue↗
PubMed1998

A randomized, placebo-controlled trial of granulocyte colony-stimulating factor administration to newborn infants with neutropenia and clinical signs of early-onset sepsis.

OBJECTIVE: To determine whether recombinant human granulocyte colony-stimulating factor (G-CSF) administration: 1) accelerates production of neutrophils; 2) increases bone marrow stored and precursor neutrophils; and 3) is safe in newborn infants with neutropenia and clinical signs of early-onset sepsis. STUDY DESIGN: We randomized 20 infants with neutropenia and clinical signs of early-onset sepsis in the first 3 days of life to receive G-CSF (10 microg/kg/d) or placebo for 3 days. Entry criteria included neutropenia as defined by Manroe criteria, an elevated immature to total neutrophil ratio [(I/T) >/=0.25], and a requirement for ventilatory support. Cultures were obtained and antibiotics initiated on all study infants. Circulating absolute neutrophil count (ANC), I/T ratio, bone marrow neutrophil storage pool (NSP) and neutrophil proliferative pool (NPP), and plasma G-CSF concentrations were evaluated. Also, severity of illness as determined using the Score for Neonatal Acute Physiology (SNAP), morbidity, and mortality were recorded. RESULTS: Circulating ANC increased in both G-CSF and placebo recipients by day 1. Also, the I/T neutrophil ratio decreased in both G-CSF and placebo recipients. There were no significant differences in the ANC or I/T ratio between the two groups during the study period. Similarly, bone marrow NSP and NPP did not differ between G-CSF and placebo recipients at study entry or day 2. No differences were observed in the secondary outcome measures including severity of illness, morbidity, and mortality. CONCLUSIONS: Administration of recombinant G-CSF to infants with neutropenia and clinical signs of early-onset sepsis did not increase circulating ANC, or bone marrow NSP and NPP compared with placebo. No differences were observed between G-CSF and placebo recipients in severity of illness, morbidity, or mortality. No adverse effects of G-CSF administrations were noted.

Bacteremia↗
PubMed1998

Burn injury.

An important element in the care of burns, which affect more than 2.5 million Americans per year, is a multidisciplinary team approach. Nurses are important members of the team, which also includes physicians, physical and occupational therapists, psychologists, rehabilitation counselors, and nutritionists among others. Regular communication with the team is important for consistent quality care.

Bandages↗
PubMed1998

Parathyroid hormone (1-34) increased total body bone mass in aged female rats.

Daily subcutaneous administration of bovine parathyroid hormone (PTH)(1-34) stimulates bone formation and increases bone mass in rat tibiae, femora and lumbar spine. However, the effects of PTH on the whole body bone mineral content and density determined by dual energy x-ray absortiometry (DEXA) have not been previously reported in rats. Eighteen-month-old intact female rats were subcutaneously injected daily with 0, 40, 80 or 160 micrograms/kg/day of bovine PTH (1-34) for either 15 or 60 days. Whole body DEXA was performed at 1 day before autopsy, and bone area, bone mineral content (BMC) and bone mineral density (BMD) of the total body were determined. Total femoral, tibial and lumbar spine BMD was also determined ex vivo. Cancellous bone histomorphometry was performed on sections of double-labeled proximal tibial metaphyses. Whole body bone mineral content and density were significantly increased by 60 days, but not by 15 days, of PTH treatment at all dose groups compared with vehicle controls. Lumbar vertebral and total femoral BMD was significantly increased at all doses of PTH by 15 days of administration and further increased by 60 days. All doses of PTH increased trabecular bone area in proximal tibial metaphyses by 15 days and further increased by 60 days. All doses of PTH increased trabecular bone area in proximal tibial metaphyses by 15 days and further increased by 60 days. In proximal tibial cancellous bone, dose-dependent increases in percent labeled perimeter, mineral apposition rate and bone formation rate-bone volume referent were found between 40 and 160 micrograms/kg of PTH treatment by 15 days, and no further increases were found by 60 days. Our results showed that in aged female rats, bovine PTH(1-34) increased bone formation and total body bone mass.

Animals↗
PubMed1997

Persistence of human leukocyte antigen (HLA) antibodies after one year in children receiving cryopreserved valved allografts.

This study shows that the broad anti-HLA antibody response against cryopreserved valved allografts used for surgical repair of congenital heart disease persists beyond 1 year after implantation. In 3 patients, there were clearly defined HLA antibody specificities consistent with the HLA phenotypes of the patients, i.e., the panel-reactive antibody was directed against major alloantigen groups that were not expressed by the antibody responders.

Adolescent↗
PubMed1997

Common mechanism for the estrogen agonist and antagonist activities of droloxifene.

The incidence of postmenopausal osteoporosis is increasing as the population ages. Even though estrogen replacement therapy has proven beneficial in reducing the number of skeletal fractures, the known risks and associated side-effects of estrogen replacement therapy make compliance poor. Recent research has focused on the development of tissue specific estrogen agonist/antagonists such as droloxifene which can prevent estrogen deficiency-induced bone loss without causing uterine hypertrophy. Furthermore, droloxifene acts as a full estrogen antagonist on breast tissue and is being evaluated for treatment of advanced breast cancer. In this report we propose a common mechanism of action for droloxifene that underlies its estrogen agonist and antagonist effects in different tissues. Droloxifene and estrogen, which have identical effects on bone in vivo, both induced p53 expression and apoptosis in cells of in vitro rat bone marrow cultures resulting in a decrease in the number of bone-resorbing osteoclasts. Droloxifene is growth inhibitory in MCF-7 human breast cancer cells and therefore acts as an antagonist, whereas estrogen is mitogenic to these cells and acts as an agonist. Droloxifene, but not estrogen, induced p53 expression and apoptosis in MCF-7 cells. These results indicate that the induction of apoptosis by droloxifene may be the common mechanism for both its estrogen agonist effects in bone and its antagonist effects in breast tissue.

Animals↗
PubMed1997

Comparative effects of droloxifene, tamoxifen, and estrogen on bone, serum cholesterol, and uterine histology in the ovariectomized rat model.

The purpose of this study was to compare the effects of droloxifene (DRO), tamoxifen (TAM), and 17 alpha-ethynyl estradiol (EE) on bone mineral density, bone histomorphometry, total serum cholesterol, and uterine histology in the ovariectomized (ovx) rat model. Sprague-Dawley female rats at five months of age were sham-operated and treated orally with vehicle (n = 8), or ovx (n = 56) and treated (p.o.) with either vehicle, DRO at 0.1 or 1.0 mg/kg daily, TAM at 0.1 or 1 mg/kg daily, or EE at 3 or 30 micrograms/kg daily for 4 weeks. The uterine wet weight and uterine histologic parameters (cross-sectional tissue area, stromal thickness, and luminal epithelial thickness) were determined. Femoral and lumbar vertebral bone mineral density was determined ex vivo using dual energy x-ray absorptiometry. Static and dynamic cancellous bone histomorphometry was performed on double-labeled, undecalcified longitudinal sections from proximal tibial metaphyses. Furthermore, the changes in total serum cholesterol and body weight gain were also determined. Compared to sham controls, ovx for four weeks significantly decreased uterine weight (-72%), uterine cross-sectional tissue area (-74%), stromal thickness (-52%), and luminal epithelial thickness (-53%). ovx rats treated with EE at 30 micrograms/kg/day maintained these parameters at the levels of sham controls. Uterine weight and uterine cross-sectional tissue area in 3 micrograms/kg/day of EE treated ovx rats were higher than that of vehicle-treated ovx rats. In ovx rats treated with TAM at both 0.1 and 1 mg/kg/day, these parameters were significantly less than sham controls but significantly higher than ovx controls. DRO at 0.1 mg/kg/day had no effects on all above parameters. Uterine weight and cross-sectional tissue area in 1 mg/kg/day of DRO treated ovx rats was slightly but significantly higher than that in ovx controls. However, DRO at 1 mg/kg/day had no effects on uterine stromal thickness and luminal epithelial thickness compared to ovx controls. The ovx-induced decrease in femoral and lumbar vertebral bone mineral density was prevented by treatment with EE at 30 micrograms/kg/day, TAM at both 0.1 and 1 mg/kg/day, or DRO at 1 mg/kg/day. Similarly, the decrease in bone mass and the increase in bone resorption and bone turnover in proximal tibial metaphyses were prevented by treatment with EE at 30 micrograms/kg/day or TAM at both 0.1 and 1 mg/kg/day, or DRO at 1 mg/kg/day. Total serum cholesterol decreased significantly in ovx rats treated with either EE, DRO, or TAM at all dose levels compared to vehicle treated ovx controls (-32% to -56%). The ovx-induced body weight gain was completely prevented by EE at 30 micrograms/kg/day, and partially prevented by DRO at 1 mg/kg/day. TAM at both 0.1 and 1 mg doses caused a significant decrease in body weight compared to both sham and ovx controls. Our results indicated that DRO prevented ovx-induced bone loss and lowered total serum cholesterol with an ED50 less than 1 mg/kg/day. The bone protective and cholesterol lowering effects of DRO were comparable to those observed with TAM and EE. However, DRO differed from TAM and EE in its lack of significant estrogenic effects on uterine tissue at doses which were bone protective. These data suggest that DRO may be a significant alternative to EE and TAM for prevention and treatment of postmenopausal osteoporosis.

Absorptiometry, Photon↗
PubMed1995

Droloxifene prevents ovariectomy-induced bone loss in tibiae and femora of aged female rats: a dual-energy X-ray absorptiometric and histomorphometric study.

Our previous studies indicated that droloxifene (DRO), a tissue-specific estrogen antagonist/agonist, prevented bone loss without causing uterine hypertrophy in growing ovariectomized (OVX) rats. Using dual-energy X-ray absorptiometry (DXA) and bone histomorphometry, the current study compared the efficacy of DRO to 17 beta-estradiol (E2) in preventing OVX-induced bone loss in tibiae and femora of 19-month-old rats to determine whether DRO had similar skeletal effects as E2 in aged female rats. Sprague-Dawley female rats were OVX or sham-operated (sham) at 19 months of age. The sham-operated rats were treated with vehicle (oral), while the OVX rats were treated with vehicle (oral), E2 at 30 micrograms/kg/day (sc), or DRO at 2.5, 5, or 10 mg/kg/day (oral) for 8 weeks. Bone mineral density (BMD) of whole femora (WF), distal femoral metaphyses (DFM), femoral shafts (FS), and proximal femora (PF) was determined using DXA. Static and dynamic cancellous bone histomorphometric analyses were performed in double-labeled undecalcified longitudinal sections from proximal tibial metaphyses. Ovariectomy for 8 weeks significantly reduced the BMD of WF, DFM, FS, and PF (from -6 to -15%). Treatment with E2 completely prevented the decreases in BMD of WF and DFM and had no significant effects in BMD of FS and PF in aged OVX rats. The decrease in BMD of DFM induced by OVX was prevented by treatment with DRO at all dose levels. In addition, DRO at 10 mg/kg/day prevented OVX-induced decreases in BMD of WF, FS, and PF.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1995

FDA Guidelines and animal models for osteoporosis.

The recent FDA Guidelines For Preclinical and Clinical Evaluation of Agents Used in the Treatment or Prevention of Postmenopausal Osteoporosis (1994) delineate specific preclinical animal models to demonstrate the efficacy and safety of new, potential agents for osteoporosis therapy. The Guidelines recommend that agents be evaluated in two animal species, including the ovariectomized (OVX) rat and in a second non-rodent model. We have performed a series of studies to determine whether the recommended OVX rat models, endpoints, and study design adequately address the efficacy and safety of therapeutic agents for the treatment or prevention of osteoporosis. Our study results indicate that the rat OVX model mimics postmenopausal cancellous bone loss when examined over relatively short periods of time. These data illustrate that cancellous bone turnover increases following OVX and this increased bone turnover produces bone loss. Estrogen completely blocks the activation of bone turnover and bone loss. Thus, our data suggest that the rat OVX model in the proximal tibia, distal femur, and lumbar vertebrae mimics conditions in the postmenopausal woman and is suitable for the evaluation of potential therapeutic agents for the prevention of osteoporosis. However, when the duration of the studies extends to 12 months as suggested by the Guidelines, the indices of cancellous bone turnover return to the value of sham controls, although the trabecular bone volume remains lower than that of sham controls in OVX rats. Therefore, it is difficult to determine the effects of potential therapeutic agents on the bone turnover in estrogen deficient conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1995

Droloxifene inhibits cortical bone turnover associated with estrogen deficiency in rats.

Droloxifene (DRO), an estrogen antagonist/agonist, has been shown to possess estrogen-like effects in inhibiting bone turnover leading to cancellous bone loss in ovariectomized (OVX) rats. The purpose of this study was to determine the effects of DRO on cortical bone turnover in OVX rats. Sprague-Dawley female rats at 5 months of age were sham-operated (sham, n = 8) and orally treated with vehicle, or OVX (n = 56) and orally treated with either vehicle, DRO at 0.1, 1, 5, or 10 mg/kg/day, or 17 alpha-ethynyl estradiol (EE) at 3 or 30 micrograms/kg/day for 4 weeks. Static and dynamic cortical bone histomorphometry was performed on double fluorescent labeled, undecalcified cross sections of tibial diaphyses (proximal to the tibiofibular junction). There were no significant differences in tibial diaphyseal cross sectional area, marrow cavity area, and cortical bone area between groups after 4 weeks of administration. Periosteal mineralizing surface, mineral apposition rate, and bone formation rate-surface referent and endocortical eroded surface increased significantly, while endocortical mineral apposition rate and bone formation rate-surface referent increased nonsignificantly in OVX controls compared to sham controls. Treatment with DRO at doses of 0.1 to 10 mg/kg/day dose-dependently attenuated the OVX-induced higher bone formation indices in both the periosteal and endocortical surfaces and higher bone resorption index in the endocortical surface. At the highest dose (10 mg/kg/day), DRO completely inhibited the increases in bone formation and resorption indices in OVX rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Effects of droloxifene on prevention of cancellous bone loss and bone turnover in the axial skeleton of aged, ovariectomized rats.

The purpose of this study was to determine the efficacy of droloxifene (DRO), an estrogen antagonist/agonist, in preventing ovariectomy (OVX)-induced lumbar vertebral cancellous bone loss and bone turnover in aged female rats. Fifty-three Sprague-Dawley female rats were OVX or sham-operated at 19 months of age, and divided into 6 groups: (I) sham-operated controls; (II) OVX vehicle controls; (III) OVX rats treated with E2 at 30 micrograms/kg/day; (IV)-(VI) OVX rats treated with DRO at either 2.5, 5, or 10 mg/kg p.o. daily. The treatment period was 8 weeks. Static and dynamic cancellous bone histomorphometric parameters were determined on 4 and 10 microns thick, undecalcified, double-fluorescent labeled sections of the fourth lumbar vertebral body. Changes in body weight, uterine weight, and total serum cholesterol were also determined. OVX for 8 weeks in 19-month-old female rats resulted in reduced trabecular bone volume (-18%) and trabecular width (-10%) and increased labeling perimeter (+52%), bone formation rate/bone surface referent (+60%), bone formation rate/bone volume referent (+77%), osteoclast number (+41%), and osteoclast perimeter (+41%). E2 treatment at 30 micrograms/kg/day for 8 weeks prevented OVX-induced cancellous bone loss and decreased bone resorption, bone formation, and bone turnover to the values of sham controls. DRO at 2.5-10 mg/kg/day completely prevented bone loss and bone turnover associated with estrogen deficiency. Osteoclast number and perimeter were significantly decreased in DRO-treated-OVX rats compared to both sham and OVX controls. Trabecular bone volume, trabecular width, labeling perimeter, bone formation rate/bone surface referent, and bone formation rate/bone volume referent showed no differences in DRO-treated OVX rats compared to those of E2-treated OVX rats and sham controls. These histomorphometric results indicated that DRO is an estrogen agonist on cancellous bone of lumbar vertebral bodies of aged, OVX rats. Further, E2 treatment prevented the OVX-induced increase in body weight gain and nonsignificantly reduced total serum cholesterol compared to OVX controls. Body weight gain and total serum cholesterol did not differ between OVX rats treated with E2 and sham controls. In OVX rats treated with DRO, body weight decreased significantly in a dose-response manner, and total serum cholesterol was significantly reduced by 65% to 70% compared to both sham and OVX controls. In addition, treatment with E2 increased uterine weight to the value of sham controls in OVX rats. However, DRO had no effect on uterine weight at either 2.5 or 10 mg/kg/day, while it only slightly but significantly increased uterine weight over OVX controls at 5 mg/kg/day. We conclude that DRO was efficacious in the prevention of lumbar vertebral cancellous bone loss and in the decline of total serum cholesterol but had no effect on uterine weight in the aged, OVX female rats. Our data suggest that DRO is a potentially useful agent for the prevention of vertebral bone loss leading to spinal fractures in postmenopausal women.

Administration, Oral↗
PubMed1995

Droloxifene, a new estrogen antagonist/agonist, prevents bone loss in ovariectomized rats.

The purpose of this study was to determine the effects of droloxifene (DRO), a new estrogen antagonist/agonist, on bone turnover, bone mass, total serum cholesterol, and uterine weight in rats made estrogen deficient by ovariectomy. Sprague-Dawley female rats were ovariectomized (OVX) or sham operated (sham) at 5 months of age and treated with 17 beta-estradiol (E2) at 30 micrograms/kg, sc, daily or with DRO at 5, 10, or 20 mg/kg.day, orally, for 4 weeks. At the time of death, body weight gain, uterine weight, and total serum cholesterol were measured. Bone area, bone mineral content (BMC), and bone mineral density (BMD) of whole femora, distal femoral metaphyses, femoral shaft, and proximal femora were determined ex vivo using dual energy x-ray absorptiometry. Static and dynamic cancellous bone histomorphometric analysis of proximal tibial metaphyses was performed in double fluorescent labeled, undecalcified, 4- and 10-microns longitudinal sections. Body weight gain in E2-treated OVX rats was significantly reduced compared to that in OVX controls, but was not different from that in sham controls. Body weight gain in DRO-treated OVX rats was decreased significantly compared to that in both sham and OVX controls. In OVX rats, uterine weight was completely preserved by treatment with E2. Uterine weight in DRO-treated OVX rats was slightly, but significantly, increased from the vehicle-treated control value, and was significantly lower than that in sham controls and E2-treated OVX rats. Treatment with sc injection of E2 in OVX rats had no effect on total serum cholesterol, whereas OVX rats orally treated with DRO at 5-20 mg/kg.day decreased total serum cholesterol by 33-46% compared to levels in sham and OVX controls. Compared to sham controls, OVX decreased BMC and BMD of distal femoral metaphyses, increased BMD of the femoral shaft, and had no effect on BMC and BMD of whole femora and proximal femora. Treatment with either E2 or DRO prevented these changes induced by OVX. Proximal tibial metaphyseal trabecular bone volume and trabecular number were increased, and trabecular separation, percent osteoclast perimeter, osteoclast number, percent mineralizing perimeter, mineral apposition rate, bone formation rate, and bone turnover rate were decreased in 5, 10, or 20 mg/kg.day DRO-treated OVX rats compared to OVX controls. These cancellous bone histomorphometric indexes in DRO treated OVX rats did not differ from those in E2-treated OVX rats or sham controls, suggesting that DRO completely prevented the increases in bone turnover and the decrease in bone mass induced by OVX in rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Presence of messenger ribonucleic acid encoding osteocalcin, a marker of bone turnover, in bone marrow megakaryocytes and peripheral blood platelets.

Osteocalcin (Oc), an abundant gamma-carboxylated protein (mol wt, 5800) of bone matrix, is used as a serum marker of bone turnover because it is considered to be uniquely synthesized by the osteoblast. Our finding of Oc messenger RNA (mRNA) in rat tibial diaphyseal marrow led us to investigate the cellular origins of Oc mRNA in peripheral blood and bone marrow. In anticoagulated blood, Oc mRNA was detected in total RNA prepared from buffy coat cells (BCC). Fractionation of rat and human blood showed that platelets contain Oc mRNA identical to that found in bone cells. In rat bone marrow, Oc mRNA is highly enriched in the platelet-producing megakaryocyte population. Depending upon the RIA used, immunoreactive Oc was either undetectable or present at very low levels in platelets and megakaryocytes, suggesting that synthesis of Oc by these cells may be under strong translational regulation. In addition, Oc levels were higher in serum vs. plasma obtained from the same blood, suggesting that Oc may be released by platelets during blood clotting. Interestingly, the magnitude of this difference was greater in female rats. Injection of 1,25-dihydroxyvitamin D3 dose-dependently increased plasma Oc, but did not cause correlative changes in steady state levels of Oc mRNA in BCC. During rat growth, plasma Oc was maximal, whereas Oc mRNA levels in BBC were low. This relationship was reversed during aging. A correlation between Oc mRNA levels in BCC and rat age suggests a developmental regulation of Oc mRNA levels in platelets. These data indicate that Oc mRNA is not restricted to cells on mineralizing surfaces, but is also found in megakaryocytes and peripheral blood platelets, which possibly contribute to the Oc levels in blood and the regulation of bone turnover.

Adult↗
PubMed1993

Pattern of gene expression following rat tibial marrow ablation.

Following injury to bone marrow there is a phase of osteogenesis in which bone trabeculae replace the initial blood clot and fill the marrow cavity. The newly formed bone is subsequently fully resorbed by osteoclasts and normal bone marrow is restored. In this study we correlated the morphologic events with the pattern of gene expression that defines this sequence. Following marrow ablation, the trabecular bone volume in the affected section of the marrow cavity increased from control to 27% at day 6, declined to 18% at day 8, and eventually returned to control levels at day 14. Osteoblast number increased up to day 6 and declined substantially by day 8, but the number of osteoclasts peaked between days 8 and 10. Histologic analysis of alkaline phosphatase (AP) and tartrate-resistant acid phosphatase (TRAP) activity correlated with the observed cellular changes. Northern blot analysis of the levels of AP, osteocalcin (OC), and osteopontin (OP) mRNA shows a specific pattern of regulated gene expression, with AP mRNA maximal at day 6, OC mRNA very low until days 6-8, and OP mRNA expressed at very high levels throughout. In addition, procollagen alpha 1(I) and alpha 1(III) mRNAs show a regulated pattern of expression, with procollagen alpha 1(I) maximally expressed between days 4 and 10 and procollagen alpha 1(III) expressed at lower levels between days 4 and 6. The mRNA encoding insulin-like growth factor I (IGF-I) was found to be highly expressed between days 5 and 12; however, transforming growth factor beta 1 (TGF-beta 1) and TGF-beta 3 mRNA were only weakly expressed between days 4 and 10. These data demonstrate a temporal pattern of gene expression consistent with the observed morphologic profile, identify changes in growth factor mRNA that may be related to this repair process, and suggest that this is a suitable model for studying in vivo a synchronized sequence of bone formation and resorption at a well-defined anatomic site.

Alkaline Phosphatase↗