Biomedical subjects

H E Gruber

Publications and source records attributed to H E Gruber.

At least 37 records · Page 2Linked to original sources

PubMed1999

Lumbar spinal fusion using recombinant human bone morphogenetic protein in the canine. A comparison of three dosages and two carriers.

STUDY DESIGN: A randomized, prospective and controlled animal study. OBJECTIVE: To evaluate lumbar spinal fusion using recombinant human bone morphogenetic protein 2 in a canine model. SUMMARY OF BACKGROUND DATA: Spinal fusion using autogenous bone grafting is associated with donor site morbidity and a nonunion rate of 5% to 35%. The use of recombinant human bone morphogenetic protein 2 as a bone graft substitute would eliminate donor site morbidity and perhaps augment the rate of successful fusion. METHODS: Mature beagles underwent bilateral paraspinal exposure at L4-L5, followed by transverse process decortication and randomization into one of six groups using differing doses of recombinant human bone morphogenetic protein 2 implanted using either a Type I collagen carrier or a polylactic acid carrier. Two control groups were used: one group without recombinant human bone morphogenetic protein 2 and another group using autogenous rib graft alone. RESULTS: Groups treated with recombinant human bone morphogenetic protein 2 demonstrated complete fusion in all animals. Animals treated with collagen carrier alone (no recombinant human bone morphogenetic protein 2) demonstrated complete absence of fusion. Successful fusion occurred in one of three canines in the autogenous bone graft group. Fusion masses in the recombinant human bone morphogenetic protein 2 treatment groups were significantly larger in size at 3 months than in the autogenous bone graft group. The collagen carrier was more biocompatible and biodegradable because residual polylactic acid carrier was seen with adjacent multinucleated giant cells. There was no evidence of spinal canal or nerve root encroachment in the recombinant human bone morphogenetic protein 2 treatment groups. CONCLUSIONS: The use of recombinant human bone morphogenetic protein 2 implanted using a Type I collagen carrier resulted in 100% fusion without adverse effects.

Animals↗

PubMed1999

Safety of recombinant human bone morphogenetic protein-2 after spinal laminectomy in the dog.

STUDY DESIGN: This was a randomized, blinded trial of the safety of the application of recombinant human bone morphogenetic protein (rhBMP)-2 or autologous bone graft onto a laminectomy defect of the dog in the presence or absence of a dural membrane puncture. OBJECTIVE: To test the safety of rhBMP-2 in an application in which direct contact of the material with neural tissue occurs. SUMMARY OF BACKGROUND DATA: Application of rhBMP-2 in laboratory animals stimulates local bone formation to effect spinal fusion and healing of segmental bone defects. The use of rhBMP-2 as a bone graft substitute in spinal fusion would eliminate donor site morbidity and may augment the rate of successful fusion. Because rhBMP-2 may unintentionally come in contact with neural tissue, the consequences of such a safety issue must be addressed in an animal model before human trials. METHODS: Twenty skeletally mature beagles underwent spinal exposure followed by bilateral laminectomy at L5. In half of the dogs, a puncture wound was made to the dura with the expression of cerebrospinal fluid at the site of the puncture. In randomly selected animals, the exposed dural elements received either autologous bone graft with the bone removed from the laminectomy site or an implant of the rhBMP-2 device. The animals was observed for 12 weeks with periodic clinical examinations and monthly computed tomographic scans. RESULTS: There was no clinical, radiographic, or histologic evidence of neurologic abnormalities in these animals. The rhBMP-2 stimulated bone growth in the laminectomy defect and came into direct contact with the dural membrane. There was no evidence of abnormal mineralization within the thecal sac or in the spinal cord itself. CONCLUSIONS: The rhBMP-2 implant stimulated bone formation in the laminectomy site. Neither autologous bone, rhBMP-2, nor the dural puncture had deleterious consequences for the animals.

Administration, Topical↗

PubMed1999

Thirty cases of concurrent Paget's disease and primary hyperparathyroidism: sex distribution, histomorphometry, and prediction of the skeletal response to parathyroidectomy.

Studies of the effect of parathyroidectomy (PTX) on bone turnover in patients with the combination of primary hyperparathyroidism (PHPT) and Paget's disease (PD) are largely limited to case reports. The etiology of the combination is disputed. We report 30 patients and their biochemical (n = 17) and histomorphometric (n = 4) responses to PTX in 18. All 18 patients except one had a post-PTX fall in plasma alkaline phosphatase (pAP). There was a significant positive correlation between the degree of post-PTX fall in pAP and both the preoperative plasma total corrected calcium (CaC) (P < 0.01) and serum ionized calcium (P < 0.05). For the patients with CaC levels >3.0 mmol/liter, the mean % fall in pAP was 68% of pretreatment (to 32%). For those with CaC levels >/=2.68 mmol/liter the fall in pAP was >18%. Of 12 literature cases treated by PTX and followed up, 11 had a postoperative fall in pAP (range 6-83%). Pretreatment bone biopsies (n = 6) could not be distinguished from uncomplicated PD. No significant histomorphometric changes were documented postoperatively in the four patients studied; however, % fibrotic surfaces declined in each of the four. Of the 18 patients, only one had radiologic subperiosteal erosions preoperatively; none had clinical tetany postoperatively-thus distinguishing this combination of diseases from severe PHPT bone disease-a situation easily biochemically confused with this combination. The sex distribution of 2.75:1 F/M in this series resembles reported ratios in pure PHPT of 2.37:1, unlike the ratios found in pure PD (0.49-1.01:1). The prevalence of PHPT in PD is 2.2-6.0% (mean 4.4%) in 1836 patients. In our series, 73% of patients with both diseases were females >60 years of age. In population studies >60 years, PHPT was present in 3% of women and 1% of men. Hypercalcemia in PD is frequently attributed to immobilization. As part of this study, we examined 184 patients referred with PD for the existence of, and cause of hypercalcemia. Of this group, 21 were hypercalcemic, 19 (90%) of whom had PHPT; none had immobilization hypercalcemia. In patients with both disorders, the indications for PTX should include the potential post-PTX improvement in pagetic biochemistry and symptoms. The sex distribution (resembling pure PHPT) and the similar prevalence of PHPT in Paget's, and in the elderly population, support the likelihood, in most cases, that these two common diseases are associated by chance.

Alkaline Phosphatase↗

PubMed1999

Anti-apoptotic actions of cytokines in mammalian cells.

Apoptosis is now widely recognized as an important mode of cell death. Since the apoptotic pathway is an active process, modulation of apoptosis is important in our understanding of cell pathophysiology. Recent data have shown the inhibition of apoptosis in different cell types exposed to certain cytokines. Therapeutics that modulate the regulation of apoptosis provide an opportunity for the treatment of certain diseases. There are many reviews for apoptosis induction and the regulators involved. The present report selects important articles on the recent data showing the anti-apoptotic ability of cytokines in mammalian cells. Other novel compounds showing anti-apoptotic functions are also reviewed.

Animals↗

PubMed1999

The influence of Matrigel or growth factor reduced Matrigel on human intervertebral disc cell growth and proliferation.

Matrigel (reconstituted basement membrane extract) is a potent inducer of cell growth and differentiation in vitro. This study examined phenotypic variation and proliferative responses of human annular intervertebral disc cells in vitro in Matrigel and Growth Factor Reduced Matrigel (GFR-Matrigel). Cells from age- and gender-matched control subjects and patients with degenerative disc disease were grown either on the surface of, or suspended within, either matrices. Disc cells grew well on top of both matrices with cells spontaneously forming cell projections. Cells grown within either matrix migrated within the gel to form colonies. Increased colony formation within the matrices was seen with young control and patient cells (p < 0.05). Old and young control and patient cells showed increased proliferation within GFR-Matrigel compared to Matrigel. When grown on the matrix surface, young patient and control donor cells showed increased proliferation on GFR-Matrigel compared to Matrigel. Cellular proliferation was significantly greater inside a 3-dimensional environment than a two-dimensional surface monolayer environment. Disc cells had increased proliferation when grown in or on GFR-Matrigel compared to Matrigel. These studies serve as a baseline for subsequent investigations regarding effects of cytokines on disc cells and increase our knowledge of the influence of extracellular matrices on disc cell proliferation.

Adult↗

PubMed1999

Detection of apoptotic cells in vitro: a practical standardized experimental protocol using human fibroblasts for initial laboratory studies.

This technical report presents a practical experimental protocol using human fibroblasts that is useful for initiating in situ methods for detection of apoptotic cells in vitro. The protocol details the growth of cells in multichamber wells, and includes a negative control, two positive controls, and untreated fibroblasts to be evaluated for apoptosis localization. Technical tips on handling of solutions, cell culture designs, and separation of slides by treatment are valuable steps for the laboratory beginning such studies. The methods proposed are both time and cost effective.

Apoptosis↗

PubMed1999

Adenosine kinase inhibitors as a novel approach to anticonvulsant therapy.

Adenosine levels increase at seizure foci as part of a postulated endogenous negative feedback mechanism that controls seizure activity through activation of A1 adenosine receptors. Agents that amplify this site- and event-specific surge of adenosine could provide antiseizure activity similar to that of adenosine receptor agonists but with fewer dose-limiting side effects. Inhibitors of adenosine kinase (AK) were examined because AK is normally the primary route of adenosine metabolism. The AK inhibitors 5'-amino-5'-deoxyadenosine, 5-iodotubercidin, and 5'-deoxy-5-iodotubercidin inhibited maximal electroshock (MES) seizures in rats. Several structural classes of novel AK inhibitors were identified and shown to exhibit similar activity, including a prototype inhibitor, 4-(N-phenylamino)-5-phenyl-7-(5'-deoxyribofuranosyl)pyrrolo[2, 3-d]pyrimidine (GP683; MES ED50 = 1.1 mg/kg). AK inhibitors also reduced epileptiform discharges induced by removal of Mg2+ in a rat neocortical preparation. Overall, inhibitors of adenosine deaminase or of adenosine transport were less effective. The antiseizure activities of GP683 in the in vivo and in vitro preparations were reversed by the adenosine receptor antagonists theophylline and 8-(p-sulfophenyl)theophylline. GP683 showed little or no hypotension or bradycardia and minimal hypothermic effect at anticonvulsant doses. This improved side effect profile contrasts markedly with the profound hypotension, bradycardia, and hypothermia and greater inhibition of motor function observed with the adenosine receptor agonist N6-cyclopentyladenosine and opens the way to clinical evaluation of AK inhibitors as a novel, adenosine-based approach to anticonvulsant therapy.

Adenosine↗

PubMed1999

Magnesium deficiency-induced osteoporosis in the rat: uncoupling of bone formation and bone resorption.

Magnesium (Mg) intake has been linked to bone mass and/or rate of bone loss in humans. Experimental Mg deficiency in animal models has resulted in impaired bone growth, osteopenia, and increased skeletal fragility. In order to assess changes in bone and mineral homeostasis that may be responsible, we induced dietary Mg deficiency in adult Simonsen albino rats for 16 weeks. Rats were fed either a low Mg diet (0.002 percent) or a normal control Mg diet (0.063 percent). Blood was obtained at baseline, 4 weeks, 8 weeks, 12 weeks and 16 weeks in both groups for serum Mg, calcium, PTH, and 1.25(OH)2-vitamin D determinations. Femora were harvested at 4 weeks and 16 weeks for mineral analysis and histomorphometry. Serum Mg fell in the Mg depleted group to 0.6 mg/dl (mean) by 16 weeks (controls = 2.0 mg/dl). The serum calcium (Ca) concentration was higher in the Mg depleted animals at 16 weeks, 10.8 mg/dl (controls = 8.9 mg/dl). Serum PTH concentration fell progressively in the Mg deficient rats to 30 pg/ml by week 16 (control = 96 pg/ml). Serum concentration of 1.25(OH)2-vitamin D also fell progressively in the Mg deficient animals by 16 weeks to 14 pg/ml (control = 30 pg/ml). While the percent ash weights of Ca and phosphorus in the femur were not different at any time point, the percent ash weight of Mg progressively fell to 0.54 percent vs control (0.74 percent) by 16 weeks. The percent ash weight of potassium also fell progressively in the Mg deficient group to approximately 30 percent of control by 16 weeks. Histomorphometric analyses showed a significant drop in trabecular bone volume in Mg deficient animals by 16 weeks (percent BV/TV = 13.2 percent vs 17.3 percent in controls). Evaluation of the endosteal bone surface features showed significantly greater bone resorption in the Mg depleted group as reflected in increased number of tartrate-resistant positive osteoclasts/mm bone surface (7.8 vs 4.0 in controls) and an elevated percent of bone surface occupied by osteoclasts (percent OcS/BS = 12.2 percent vs 6.7 percent in controls. This increased resorption occurred in the presence of an inappropriate lowered bone forming surface relative to controls; a decreased number of osteoblasts per mm bone surface (0.23 vs 0.94 in control) and a decrease in percent trabecular surface lined by osteoid (percent OS/BS = 0.41 vs 2.27 percent in controls) were also noted. Our findings demonstrate a Mg-deficiency induced uncoupling of bone formation and bone resorption resulting in a loss of bone mass. While the fall in PTH and/or 1.25(OH)2-D may explain a decrease in osteoblast activity, the mechanism for increased osteoclast activity is unclear. These data suggest that Mg deficiency may be a risk factor for osteoporosis.

Animals↗

PubMed1998

Cellular ingrowth and thickness changes in poly-L-lactide and polyglycolide matrices implanted subcutaneously in the rat.

Highly porous matrices of poly-L-lactide (PL) and polyglycolide (PG), 24, 50, or 95 mg/cc in the form of 10 x 10 x 3 mm wafers, were implanted subcutaneously (two per rat) in the flanks of 8-12-week-old female Lewis rats (n = 120). Matrices were harvested, two rats per week, for 15 weeks and examined histologically. At weeks 1 and 2, a thin fibrous capsule was present and matrices showed capillary beds and host-cell infiltration along the implant margins. By week 4, the PL specimens had some arterioles while the PG specimens still had only capillary beds. At week 7, PL had well developed arterioles, venules, and capillaries while PG began to show modest vascular beds of capillaries only. In terms of cellular ingrowth, PL remained unchanged from 7 to 15 weeks. Giant cell formation was observed wherever polymer was present. There was a loss of thickness and cell mass for both matrices over time (PG > PL) despite initial host-cell ingrowth. As both polymers degraded and were absorbed, the ingrown cells mass regressed. There was little remaining PG at 15 weeks, leaving no trace of cells that previously had ingrown and no evidence of scar tissue.

Animals↗

PubMed1998

Analysis of aging and degeneration of the human intervertebral disc. Comparison of surgical specimens with normal controls.

STUDY DESIGN: A prospective analysis of 33 control and 39 surgical human lumbar disc specimens from the anulus was undertaken to assess disc cell extracellular matrix production and cell function. The authors of this study analyzed immunohistochemical distributions of Types I, II, III and VI collagen, in situ localization of apoptotic disc cells, and tartrate-resistant acid phosphatase localization. OBJECTIVES: To quantify the incidence of apoptotic cell death in the anulus; examine the collagen distribution in the pericellular, territorial, and interterritorial matrix; examine matrix cell degeneration; and compare diseased tissue with normal tissue from control individuals. SUMMARY OF THE BACKGROUND DATA: Previous studies of disc histopathology have focused on extracellular matrix morphology and on biochemical synthetic and degenerative changes, but little is understood about the cell populations within the disc that are responsible for these changes. METHODS: In this study light microscopy, immunohistochemistry, enzyme histochemistry, and in situ hybridization were used to examine 33 patient and 39 control specimens of human anulus obtained either via surgical procedures or from donors to the Cooperative Human Tissue Network. RESULTS: The high incidence of apoptotic cell death was significantly greater in the control group (73.1 +/- 5.1% [mean +/- SEM]; n = 20) than among surgical specimens (53.5 +/- 5.6%; n = 20; P < 0.001); this was probably a result of the significantly greater average age in the control population (57.2 +/- 3.1 years) compared with that in the patient population (44.3 +/- 3.2 years; P < 0.001). Immunohistochemistry yielded findings that led to an expanded appreciation of the greatly modified extracellular domains that surrounded disc cells during aging and degeneration in both study groups. Enzyme histochemistry revealed the presence of tartrate-resistant acid phosphatase activity in human disc cells. CONCLUSIONS: These findings reveal that there is a high incidence of apoptosis in the intervertebral disc. Surviving cells are not synthetically inactive but are, rather, producing inappropriate matrix products during aging and degeneration. In certain instances it appears that the matrix surrounding the cell may form an isolation barrier, which may influence individual cell activity and intercellular communication. These results point to the need to 1) more fully understand the cause of disc cell death via apoptosis and to determine whether this programmed cell death can be reversed or halted, and 2) more fully understand the dynamic relation between disc cells and the surrounding extracellular matrix, which they produce and remodel. The factors regulating extracellular matrix-disc cell homeostasis in the disc are unknown, as is the relation between extracellular matrix and disc cell functional modulation. The morphologic findings of this study suggest that these issues are important considerations in disc cell biology. The identification of tartrate-resistant acid phosphatase activity in disc cells allows for a new area of study of disc extracellular matrix remodelling. In summary, these new perspectives provide new parameters with which to assess disc cell health and function.

Adult↗

PubMed1998

Effects of surgical approaches for acetabular fractures with associated gluteal vascular injury.

OBJECTIVES: To examine the viability of the abductor muscles following extensile exposures to the acetabulum in the presence of superior gluteal artery (SGA) or vein (SGV) injury. DESIGN: In vivo animal study. INTERVENTION: Twenty-two dogs underwent either an extensile or combined two-incision acetabular approach; either the SGA, the SGV, or no vessel was ligated. MAIN OUTCOME MEASUREMENTS: Blood flow to the affected gluteal region was evaluated by angiography, laser Doppler flowmetry, and fluorescent microspheres, and histologic and wet weight analyses were performed on the abductor muscles. RESULTS: Complete ischemic necrosis of the abductor muscles did not occur in any specimen; however, there were statistically significant reductions in immediate postoperative gluteal muscle perfusion (-47 percent, p < 0.01), loss of abductor muscle mass (-41 percent, p < 0.001), and histologic evidence of moderate to severe necrosis in five of seven specimens with extensile exposures and SGA ligation (p = 0.01). Extensile exposure and SGV ligation also caused a significant loss of muscle mass (-25 percent, p < 0.02), with moderate to severe necrosis occurring in four of seven specimens (p < 0.04). Dogs with SGA ligation undergoing the two-incision approach had no significant changes in muscle mass (-3 percent) or perfusion. Moderate to severe necrosis occurred in only one of four specimens. CONCLUSIONS: This study fails to support the hypothesis that extensile approaches to complex acetabular fractures eliminate abductor collateral circulation when performed in the presence of SGA injury.

Acetabulum↗

PubMed1998

Magnesium deficiency induces bone loss in the rat.

Disorders in which magnesium (Mg) depletion is common have an associated high incidence of osteoporosis. Mg depletion in humans results in hypocalcemia, low serum parathyroid hormone (PTH) and 1, 25(OH)2-vitamin D levels, as well as PTH and vitamin D resistance which may serve as mechanisms for the development of osteoporosis. In order to determine if isolated Mg depletion will result in bone loss, we have induced dietary Mg deficiency in the rat. Adult (290 g) female rats were given either a low-Mg diet (2 mg/100 g chow; n = 6) or a normal control Mg diet (63 mg/100 g chow; n = 6). Dietary calcium (Ca) was normal in both groups (592 mg/100 g chow). At 12 weeks, blood was obtained for serum Mg, Ca, PTH, 1,25(OH)2-vitamin D, and osteocalcin determinations. The rats were then euthanized and the femurs obtained for mineral analysis and histomorphometry. Serum Mg in the low-Mg group was less than control (0.4 +/- 0.2 vs. 1.9 +/- 0.2 mg/dl, p < 0.001; mean +/- SD) while serum Ca was higher (11. 7 +/- 0.5 vs. 9.3 +/- 0.4 mg/dl, p < 0.001). PTH was suppressed in the Mg-deficient group (36 +/- 16 vs. 109 +/- 30 pg/ml in controls, p < 0.002). Serum 1,25(OH)2-vitamin D was also suppressed in the Mg-deficient animals (7.1 +/- 4.8 vs. 28.5 +/- 8.2 pg/ml in controls, p < 0.002). Serum osteocalcin levels were not different (19.8 +/- 2.5 ng/ml in Mg-deficient rats vs. 15.3 +/- 3.4 ng/ml in controls). While the ash weight of Ca and phosphorus in the femur did not change, the ash weight of Mg fell (low-Mg group 0.55 +/- 0.01%, controls 0.65 +/- 0.02%, p < 0.001). Histomorphometry demonstrated reduction in bone mass; the trabecular bone volume in the femur of the low-Mg group was reduced from control (7.7 +/- 0.2 vs. 13.7 +/- 1.9%, p < 0.002). A surprising new observation was an increase in osteoclast (OC) bone resorption with Mg depletion. The number of OC per millimeter bone surface was 16.9 +/- 1.3 in the low-Mg group versus 7.8 +/- 1.5 in controls (p < 0.001). The percentage of bone surface occupied by OC was 38.3 +/- 3.7 in the low-Mg group versus 17.7 +/- 2.4 in controls (p < 0.001). This increased resorption occurred with an inappropriate non-altered bone-forming surface relative to control (% osteoid surface: low-Mg group 2.4 +/- 0.7 vs. controls 2.6 +/- 0.4; % osteoid volume: low-Mg group 0.25 +/- 0.09 vs. controls 0.38 +/- 0.06; number of osteoblasts per millimeter bone surface: low-Mg group 0.9 +/- 0.3 vs controls 1.3 +/- 0.3). No increase in bone-forming surface or osteoblast number despite an increase in OC-resorbing surface and OC number strongly suggests impaired activation of osteoblasts and an uncoupling of bone formation and bone resorption. Our data demonstrate that Mg depletion in the rat alters bone and mineral metabolism which results in bone loss.

Animal Nutritional Physiological Phenomena↗

PubMed1997

Human intervertebral disc cells from the annulus: three-dimensional culture in agarose or alginate and responsiveness to TGF-beta1.

Cell culture procedures were developed for use with surgical and normal control specimens of the annulus of the human intervertebral disc. Cells were established in monolayer explant culture and seeded into three-dimensional growth environments of alginate or agarose; under these growth conditions cells assumed a rounded phenotype and formed colonies. A novel method of layering suspensions of cells onto cell well inserts proved technically much easier than the microbead culture method. Immunohistochemistry was utilized to demonstrate in vitro production of the following extracellular matrix components: types I, II, III, and VI collagen, 4-S-chondroitin sulfate, and keratan sulfate. Young and old age- and gender-matched cells grown in the presence of TGF-beta1 showed significant enhancement of proliferation after 4 days of exposure to TGF-beta with a lessened mitogenic response present after 10 days. Molecular studies of proteoglycan gene expression showed that at 4 days young normal cells had increased biglycan, but not decorin, message levels. Decorin expression was unchanged at Day 4 and decreased or shut off by Day 10. Results support the use of three-dimensional culture systems for in vitro evaluation of human disc cell function and expand our understanding of the in vitro behavior of these cells.

Adult↗

PubMed1997

Characterization and phenotypic stability of human disc cells in vitro.

Successful in vitro studies of disc cells require interaction of the cell with a compatible microenvironment which favors expression of the disc cell phenotype. The objective of this study was to characterize cells grown by standardized methods of isolation and passage, and culture cells from the human annulus in three-dimensional culture. Cells from the annulus of 11 individuals were cultured in alginate or agarose for ten days, and extracellular matrix components were evaluated with immunohistochemistry and quantitative analysis of the percent of colonies producing Type I or II collagen, 4-sulfated chondroitin sulfate or keratan sulfate. Results show production of these four extracellular matrix products through multiple passages and support the phenotypic stability of disc cells in three-dimensional culture.

Analysis of Variance↗

PubMed1997

Large specimen bone embedment and cement line staining.

Undecalcified embedment of large bone specimens is often challenging. A method is presented here that is suitable for methacrylate embedment of sections of canine vertebrae while retaining the ability to localize tartrate-resistant acid phosphatase and alkaline phosphatase activity. Specimens also retained tetracycline labelling, and sectioned preparations were readily stained with routine bone procedures. A modification of the Bodian silver stain, used for examining the nerves and spinal cord in these specimens, provided a useful stain for canaliculi and cement lines in trabecular and cortical bone. This stain is advantageous when both bone and nerve tissue are of interest, as in spinal fusion studies.

Animals↗

PubMed1997

Osteopenia induced by long-term, low- and high-level exposure of the adult rat to lead.

The skeleton, the major site for Pb accumulation, is responsible for the largest fraction of the total body burden, but long-term effects of low-level exposure in adults remain unclear. In this study rats were exposed to low (0.01%; 100 ppm, LoPb) or high (0.5%, 5,000 ppm, HiPb) Pb, low calcium, feeding regimes for 1-12 months. Both LoPb and HiPb animals showed significant 12-month blood Pb levels [LoPb 21 +/- 3 micrograms/dl; HiPb 59 +/- 18; controls 3 +/- 1 (mean +/- SEM), p = 0.001]. Dual energy X-ray densitometry of the femur detected a significant decrease in bone density in HiPb animals by 3 months which remained significantly lowered through 12 months [3 months: HiPb: 0.498 +/- 0.011 (6) vs. control: 0.546 +/- 0.012 (6), p < 0.003]. By 12 months' density was also significantly lowered in LoPb animals (p = 0.001). Mineral analyses of ashed femurs showed a significant lead content after 1, 3, 9 and 12 months' exposure [1 month: LoPb, 0.020 +/- 0.002 (4) (% ash weight) vs control 0.008 +/- 0.0004 (4); HiPb 0.016 +/- 0.001 (8); control 0.007 +/- 0.0004 (6) (p < or = 0.002)]. Ca levels (% ash weight) were significantly lowered at 9 months in HiPb and 12 months in both groups (p < or = 0.04). Quantitative histomorphometry documented significantly elevated osteoid and resorptive trabecular surface features in both Pb groups. The LoPb design produced no overt renal functional abnormalities and resulted in blood Pb values comparable to those in man with modest environmental Pb exposure. The HiPb design resulted in development of lead nephropathy (more severe from months 6-12) and produced blood lead levels comparable to those seen in past industrial exposure. Findings show that Pb is incorporated into bone mineral after only 1 month's exposure to LoPb with significant osteopenia after 12 months' exposure; HiPb caused osteopenia by 3 months. No normal compensatory mechanism was elicited to maintain bone mass. Results stress renewed concern about the effects of cumulative, low-level lead exposure in our elderly population.

Absorptiometry, Photon↗

PubMed1997

Comparison of human osteoblasts and osteogenic cells from heterotopic bone.

Heterotopic ossification is a common complication in which bone develops in soft tissues. Although frequently benign, in some patients the condition becomes painful, restricts motion, and requires surgical intervention. This condition and the cells responsible for it are poorly characterized. Using cell culture techniques, this study compares the performance of osteogenic cells obtained from heterotopic ossification with trabecular osteoblasts isolated from the same patient. Cells isolated from trabecular bone samples and heterotopic ossification sites from six patients were evaluated for osteocalcin production after exposure to 1,25-dihydroxycholecalciferol, alkaline phosphatase activity, typing and synthesis of collagen, cell proliferation, and total protein content. Samples of heterotopic ossification and trabecular bone from three of the patients were examined histologically. Heterotopic ossification derived cells were shown to produce osteocalcin, Type 1 collagen, and alkaline phosphatase activity. They also had increased rates of collagen synthesis, alkaline phosphatase activity, and cell proliferation compared with the normal osteoblasts. Initial tissue from the heterotopic ossification sites showed increased numbers of osteocytes/mm2 compared with normal trabecular bone. Although heterotopic ossification derived cells functioned qualitatively like osteoblasts, they exhibited elevated levels of activities traditionally ascribed to osteoblasts, such as collagen synthesis and alkaline phosphatase activity.

Adult↗

PubMed1996

Hypoglycaemic effect of AICAriboside in mice.

We have previously demonstrated that in isolated hepatocytes from fasted rats, AICAriboside (5-amino 4-imidazolecarboxamide riboside), after its conversion into AICAribotide (AICAR or ZMP), exerts a dose-dependent inhibition on fructose-1,6-bisphosphatase and hence on gluconeogenesis. To assess the effect of AICAriboside in vivo, we measured plasma glucose and liver metabolites after intraperitoneal administration of AICAriboside in mice. In fasted animals, in which gluconeogenesis is activated, AICAriboside (250 mg/kg body weight) induced a 50% decrease of plasma glucose within 15 min, which lasted about 3 h. In fed mice, glucose decreased by 8% at 30 min, and normalized at 1 h. Under both conditions, ZMP accumulated to approximately 2 mumol/g of liver at 1 h. It decreased progressively thereafter, although much more slowly in the fasted state. Inhibition of fructose-1,6-bisphosphatase was evidenced by time-wise linear accumulations of fructose-1,6-bisphosphate, from 0.006 to 3.9 mumol/g of liver at 3 h in fasted mice, and from 0.010 to 0.114 mumol/g of liver at 1 h in fed animals. AICAriboside did not significantly influence plasma insulin or glucose utilization by muscle. We conclude that in vivo as in isolated hepatocytes, AICAriboside, owing to its conversion into ZMP, inhibits fructose-1,6-bisphosphatase and consequently gluconeogenesis.

Adenosine Triphosphate↗