PubMed Health⌕ Search

Biomedical subjects

R W Boyce

Publications and source records attributed to R W Boyce.

9 recordsLinked to original sources
PubMed1992

Contrasting effects of parathyroid hormone and insulin-like growth factor I in an aged ovariectomized rat model of postmenopausal osteoporosis.

Agents that exert anabolic effects on bone have generally been tested in young or estrogen-replete animals. It is unclear whether these agents exert similar effects in older ovariectomized (Ovx) animals. In this single study we examined the effects of intermittent (daily) human PTH-(1-34) and continuous infusion of human recombinant IGF-I alone and in combination on bone resorption and formation over a 14 day period in an aged Ovx rat model of postmenopausal osteoporosis (2-year-old rats, Ovx at 1 year). Compared to Ovx controls, PTH treatment increased bone mineral content (BMC) and bone volume and stimulated bone formation but had no effect on bone resorption. In contrast, IGF-I treatment reduced BMC and stimulated resorptive activity as assessed by increases in marrow volume, cortical porosity, osteoclast-positive eroded surfaces, and urinary hydroxyproline excretion. IGF-I had no effect on bone formation, but when combined with PTH, IGF-I blunted the response to PTH on the periosteal and endocortical surfaces. In summary, PTH stimulated bone formation in a manner similar to that observed in younger animals and IGF-I stimulated bone resorption rather than formation and blunted the bone-forming response to PTH. The effects of IGF-I in older Ovx rats may differ from those observed in younger estrogen-replete animals.

Aging↗
PubMed1991

Physical fitness capacity and absenteeism of police officers.

Police officers (n = 514) were studied to determine the relationship between physical fitness capacity and annual absenteeism rate. Hierarchical regression analyses revealed that for officers aged 34 years and younger, only 5% of the variability in absenteeism could be accounted for by age, sex, and physical fitness variables. For officers 35 years old and older, 7% of the variability was explained by these variables, and a bicycle ergometer score was a significant predictor of absenteeism. Each individual test and an overall physical fitness score were classified into five levels. ANOVAs revealed no significant differences between overall fitness levels and absenteeism. However, men 35 and over who were most fit on the bicycle ergometer test had fewer absences, and women 34 and under who were thinnest had more absences. In conclusion, at least among police officers, the extent to which physical fitness capacity can predict absenteeism is low.

Absenteeism↗
PubMed1990

Sequential histomorphometric changes in cancellous bone from ovariohysterectomized dogs.

To evaluate potential pharmacologic agents for the prevention or treatment of the bone loss associated with ovarian insufficiency, a predictable animal model is needed. To assess the potential utility of the ovariohysterectomized dog as a model of this condition, we characterized the sequential histomorphometric changes in canine cancellous bone in response to the loss of ovarian function. A group of 25 adult beagle dogs were ovariohysterectomized and terminated at 1, 3, 6, and 10 months following surgery. Iliac biopsies were performed following double-fluorochrome labeling at the time of surgery and at termination. Static and dynamic histomorphometry was performed on undecalcified sections. By 3 months postovariohysterectomy, there was activation of cancellous bone remodeling as indicated by significant increases in mineralizing surface and bone formation rate. Increases in osteoid surface, mineralizing surface, and bone formation rate were also apparent at 1 month postovariohysterectomy, and although not statistically significant, these trends suggest the skeletal response to acute loss of ovarian function was rapid. This increase in bone remodeling was transient. By 6 months, mineralizing surface and bone formation rate were depressed below presurgical levels. In addition to a reduction in bone formation, a reduction in osteoblast function characterized by reduced labeling of osteoid and a disproportionate increase in eroded surface also occurred. By 10 months postovariohysterectomy, cancellous bone remodeling was not significantly different from presurgical levels. At no time was a significant reduction in bone volume detected. These data suggest that the changes in cancellous bone remodeling in the ovariohysterectomized dog are a series of transient phenomena.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

NE-58095: a diphosphonate which prevents bone erosion and preserves joint architecture in experimental arthritis.

The rat adjuvant arthritis model, like human rheumatoid arthritis, is characterized by fulminating intra- and periarticular inflammation and bone lysis. This model was used to determine the effectiveness of a potent antiresorptive diphosphonate (NE-58095: monosodium [2-(3-pyridinyl) ethylidene] hydroxy diphosphonate) prophylactically in Lewis rats and therapeutically in Sprague-Dawley rats. Modified Freund's adjuvant (MFA) was injected into the tail of Lewis and Sprague-Dawley rats. Prophylactic treatment in Lewis rats [oral (PO): 14.8 mg/kg/day); subcutaneous (SC): 0.148 mg/kg/day] was begun on the day of MFA injection. A significant reduction in paw swelling was seen as early as day 12 after MFA injection with both oral and parenteral treatment. NE-58095 produced a reduction in paw swelling of 28, 39 and 61% on days 12, 17 and 24 respectively, as compared to the saline-treated MFA control. Bone lysis in the saline-treated MFA group was 85% of total possible incidence for 6 joint regions in the hind paws and 4 regions in the front paws at day 24. This resorption was reduced by 70% in the rats administered NE-58095 PO and SC at 24 days after MFA. In the therapeutic experiments with Sprague-Dawley rats, treatment with NE-58095 (SC: 0.148 mg/kg/day) was begun on day 14 after MFA injection, at which time significant paw swelling (greater than 0.5cc) had occurred. On day 25 (12 days of treatment), paw swelling was reduced 70% by NE-58095 treatment as compared to the saline-treated MFA controls. Histologically, the architecture of the tibio-tarsal joints in the saline-treated MFA rats was affected, in contrast to the NE-58095-treated MFA rats where the architecture of the joint was preserved. This new potent diphosphonate is not an anti-inflammatory compound by any of the classical tests and is effective both orally and parenterally. The mechanism by which this diphosphonate protects joint integrity is not clear but appears to be related to its ability to block bone resorption and the consequent inhibition of the diffusion into the joint space of calcium, chemotactic factors and cytokinas released from bone matrix, resulting in a quenching of the arthritic process.

Animals↗
PubMed1988

Teratocarcinoma of the ovary in a mare.

A 5-year-old Appaloosa mare had a history of mild intermittent abdominal discomfort and clinical signs that were suggestive of intestinal obstruction. Palpation per rectum revealed a large mass attached to the left uterine horn, with smaller masses extending dorsally and cranially and causing constriction of the rectum. At necropsy, numerous multilobulated masses were observed in the abdominal cavity and several nodules were seen in the lungs. The left ovary was large and contained both cartilage and hairlike material. Sections from all masses had similar histologic features and confirmed the tentative diagnosis of teratocarcinoma.

Animals↗
PubMed1985

Ultrastructural development of hyperosteoidosis in 1,25(OH)2D3-treated rats fed high levels of dietary calcium.

To evaluate the sequential ultrastructural pathogenesis of the increase in osseous tissue and hyperosteoidosis previously demonstrated in rats administered supraphysiologic doses of 1,25(OH)2D3 and fed high levels of dietary calcium, young adult female rats were placed on a 2.5% calcium and 0.3% phosphorus diet, administered ethanol or 135 ng (5 units) 1,25(OH)2D3 IP daily, and killed after 2, 4, 6, 8, and 10 days. Metaphyseal trabeculae from 1,25(OH)2D3 and placebo-treated rats were examined. Osteoblast hypertrophy characterized by increased cytoplasmic area, abundant rough endoplasmic reticulum, and prominent Golgi apparatus was evident in 1,25(OH)2D3-treated rats at Day 4. These osteoblasts were interpreted to be active in matrix synthesis. Widened osteoid seams were present at Day 6. Osteoblast hypertrophy and widened osteoid seams persisted through Day 10 in 1,25(OH)2D3-treated rats. The unmineralized bone matrix in 1,25(OH)2D3-treated rats contained more numerous cytoplasmic processes from adjacent osteoblasts than did control animals and loosely arranged collagen fibrils, which failed to aggregate in regions adjacent to the osteoid-mineralized bone interface as in placebo-treated rats. Osteoid seams in 1,25(OH)2D3-treated rats contained irregular electron-dense foci, which were often concentrated around embedded cytoplasmic processes. Osteocytic hypertrophy characterized by increased cytoplasmic area, developed rough endoplasmic reticulum, and increased numbers of mitochondria was evident at Day 2 and was sustained through Day 10 in 1,25(OH)2D3-treated rats. Variable-sized aggregates of electron-dense deposits similar to those concentrated around osteoblast cytoplasmic processes were observed in the pericellular space and on and immediately adjacent to the plasma membranes of osteocytes and embedding osteoblasts in 1,25(OH)2D3-treated rats as early as Day 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Histogenesis of hyperosteoidosis in 1,25(OH)2D3-treated rats fed high levels of dietary calcium.

The purpose of this investigation was to determine by sequential quantitative morphometry the histogenesis of metaphyseal changes induced in rats fed high levels of dietary calcium and treated with pharmacologic doses of 1,25(OH)2D3. Young adult female rats were placed on a diet containing 2.5% calcium and 0.3% phosphorus and administered either ethanol or 135 ng (5 units) 1,25(OH)2D3 in ethanol IP daily for 10 days. Rats were terminated at Days 1, 2, 3, 4, 6, 8, and 10. At Day 1 the proximal tibias from rats treated with 1,25(OH)2D3 had a dramatic increase in osteoclasts/mm total trabecular surface perimeter compared with placebo-treated rats. Osteoclast numbers decreased in 1,25(OH)2D3-treated rats to the levels in placebo-treated rats by Days 3 and 4 and decreased significantly below placebo-treated levels at Days 6, 8, and 10. Active resorbing surface was significantly increased at Days 1 and 2 and decreased at Days 8 and 10 in 1,25(OH)2D3-treated rats compared with placebo-treated rats. From Day 4 through Day 10 in 1,25(OH)2D3-treated rats, there was a progressive increase in osteoblasts/mm total trabecular surface perimeter, osteoid surface, active osteoid surface, and metaphyseal osteoid. Metaphyseal osteoid increased markedly at Days 8 and 10 in 1,25(OH)2D3-treated rats and caused a significant increase in the amount of osseous tissue in the metaphysis. Metaphyseal mineralized bone, however, was not consistently affected by 1,25(OH)2D3 treatment. Serum calcium and phosphorus were elevated in 1,25(OH)2D3-treated rats at more time periods. In rats fed high levels of dietary calcium, repeated supraphysiologic doses of 1,25(OH)2D3 result in a net increase in metaphyseal osseous tissue, predominantly osteoid.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗