Osteoclast-derived activity in the coupling of bone formation to resorption.

The cells of bone and the immune system communicate by means of soluble and membrane-bound cytokines and growth factors. Through local signalling mechanisms, cells of the osteoblast lineage control the formation and activity of osteoclasts and, therefore, the resorption of bone. Both T and B lymphocytes produce activators and inhibitors of osteoclast formation.

Astrocytic function assessed from 1-14C-acetate metabolism after temporary focal cerebral ischemia in rats.

Astrocytes play many roles essential for normal brain activity. The ability of these cells to recover after temporary focal cerebral ischemia is likely to be one important determinant of the extent of brain dysfunction and tissue damage. We have assessed astrocytic function based on the incorporation of radiolabel from 1-14C-acetate into glutamine at 1 hour of recirculation after middle cerebral artery occlusion for 2 or 3 hours in rats.

Terminal osteoblast differentiation, mediated by runx2 and p27KIP1, is disrupted in osteosarcoma.

The molecular basis for the inverse relationship between differentiation and tumorigenesis is unknown. The function of runx2, a master regulator of osteoblast differentiation belonging to the runt family of tumor suppressor genes, is consistently disrupted in osteosarcoma cell lines. Ectopic expression of runx2 induces p27KIP1, thereby inhibiting the activity of S-phase cyclin complexes and leading to the dephosphorylation of the retinoblastoma tumor suppressor protein (pRb) and a G1 cell cycle arrest.

Mitochondrial glutathione: a modulator of brain cell death.

The small fraction of glutathione in mitochondria in nonneural tissues is an important contributor to cell survival under some conditions. However, there has been only limited characterization of the properties and function of mitochondrial glutathione in cells from the brain. In astrocytes in culture, highly selective depletion of this glutathione pool does not affect cell viability, at least in the first 24 h, but does greatly increase susceptibility to exposure to nitric oxide or peroxynitrite.

Highly selective and prolonged depletion of mitochondrial glutathione in astrocytes markedly increases sensitivity to peroxynitrite.

Glutathione, a major endogenous antioxidant, is found in two intracellular pools in the cytoplasm and the mitochondria. To investigate the importance of the smaller mitochondrial pool, we developed conditions based on treatment with ethacrynic acid that produced near-complete and highly selective depletion of mitochondrial glutathione in cultured astrocytes. Recovery of mitochondrial glutathione was only partial over several hours, suggesting slow net uptake from the cytoplasm.

Effects of support surface relief pressures on heel skin blood flow in persons with and without diabetes mellitus.

Objective: To investigate the effects of pressure relief magnitude on heel blood hyperemia in persons with and without diabetes mellitus.

Design: Study participants (1 group of persons with diabetes and 1 group without diabetes) lay on a support surface for 70 minutes with 1 heel on an end cell of a support surface. Cell pressure was computer controlled to be 20 mm Hg during support and 5 or 0 mm Hg during relief.

Targeting osteoclasts with zoledronic acid prevents bone destruction in collagen-induced arthritis.

Objective: To study the effect of zoledronic acid (ZA) on synovial inflammation, structural joint damage, and bone metabolism in rats during the effector phase of collagen-induced arthritis (CIA).

Methods: CIA was induced in female dark agouti rats. At the clinical onset of CIA, rats were assigned to treatment with vehicle or single subcutaneous doses of ZA (1.

Osteopenia in Siah1a mutant mice.

Siah1a has been implicated in numerous signaling pathways because of its ability to induce ubiquitin-mediated degradation of many protein substrates. Siah1a knockout mice are growth-retarded, exhibit early lethality, and display spermatogenic defects. In this study we identified a striking low bone volume phenotype in these mice (trabecular bone volume was halved compared with wild type mice), linking Siah1a to bone metabolism for the first time.

Increased mitochondrial permeability in response to intrastriatal N-methyl-D-aspartate: detection based on accumulation of radiolabel from [3H]deoxyglucose.

Induction of the mitochondrial permeability transition has been proposed as an important contributor to cell loss in several neurological disorders, but the evidence that this change can develop in cells in the intact mature brain is largely indirect. In this study, we have tested whether an intrastriatal injection of N-methyl-D-aspartate results in increases in inner membrane permeability that can be detected from mitochondrial accumulation of metabolites of 3H-deoxyglucose previously taken up by brain cells. An increase in incorporation of deoxyglucose metabolites was found in mitochondria prepared from the striatum but not from cerebral cortex distant from the injection site.

Glycoprotein 130 regulates bone turnover and bone size by distinct downstream signaling pathways.

The gp130-dependent cytokines, which signal through at least two intracellular pathways, regulate osteoclast and osteoblast formation. To define their roles in regulating bone mass, we analyzed mice in which gp130 signaling via either the signal transducer and activator of transcription (STAT) 1/3 (gp130(DeltaSTAT/DeltaSTAT)) or SHP2/ras/MAPK (gp130(Y757F/Y757F)) pathway was attenuated. In gp130(DeltaSTAT/DeltaSTAT) mice, trabecular bone volume (BV/TV) and turnover were normal, but bone length was reduced by premature growth plate closure, indicating an essential role for gp130-STAT1/3 signaling in chondrocyte differentiation.

Glutathione monoethyl ester provides neuroprotection in a rat model of stroke.

Oxidative stress plays an important role in the development of tissue damage following transient focal cerebral ischaemia. Glutathione is a central component in the antioxidant defence of cells. We have previously shown a close association between mitochondrial glutathione loss and cell death following middle cerebral artery (MCA) occlusion.

Generation and analysis of Siah2 mutant mice.

Siah proteins function as E3 ubiquitin ligase enzymes to target the degradation of diverse protein substrates. To characterize the physiological roles of Siah2, we have generated and analyzed Siah2 mutant mice. In contrast to Siah1a knockout mice, which are growth retarded and exhibit defects in spermatogenesis, Siah2 mutant mice are fertile and largely phenotypically normal.

Gp130-mediated signaling is necessary for normal osteoblastic function in vivo and in vitro.

Previous studies have shown that mice missing gp130, the common receptor subunit for many cytokines, die at or before birth with multiple skeletal abnormalities. Furthermore, interactions between PTH and gp130 signaling have suggested that gp130 signaling might influence calcium homeostasis. We, therefore, examined the function of osteoblasts, osteoclasts, and calcium homeostasis in gp130(-/-) mice, both in vivo and in vitro.

Heel skin hyperaemia: direct compression versus vascular occlusion.

Vulnerability of the heel to ulceration in bed-bound persons is related to direct pressure-induced blood flow decreases. Periodic pressure reduction is a clinical strategy to help prevent ulcers by allowing flow-repayment hyperaemia that has a magnitude and duration thought to be related to the duration of the prior interval of ischaemia. However, there are reasons to question whether effects of flow stoppages caused by direct tissue loading are similar to those because of ischaemia without superimposed direct pressure.

Glutathione monoethylester prevents mitochondrial glutathione depletion during focal cerebral ischemia.

Glutathione is a central component in the antioxidant defences of cells. We have recently reported an early and selective loss of total (reduced plus oxidised) glutathione from mitochondria isolated from rat brain following occlusion of the middle cerebral artery. This mitochondrial glutathione depletion showed an apparent association with the tissue damage that developed during subsequent reperfusion, suggesting that it could be an important determinant of susceptibility to cell loss.

Losses of NG2 and NeuN immunoreactivity but not astrocytic markers during early reperfusion following severe focal cerebral ischemia.

The ability of glia to recover essential functions following a period of focal cerebral ischemia is likely to be one important factor influencing the severity of tissue damage that subsequently develops. In this study, we have compared changes in immunoreactivity of markers specific for astrocytes, NG2-positive glia and neurons in tissue subregions during early reperfusion following 3 h of middle cerebral artery occlusion to provide insights into possible differential susceptibility of these cell populations. Under the conditions used, infarction ultimately encompasses most of the perfusion territory of the occluded artery.

Fluorocitrate-mediated astroglial dysfunction causes seizures.

A role for astroglia in epileptogenesis has been hypothesised but is not established. Low doses of fluorocitrate specifically and reversibly disrupt astroglial metabolism by blocking aconitase, an enzyme integral to the tricarboxylic acid cycle. We used cerebral cortex injections of fluorocitrate, at a dose that we demonstrated to inhibit astroglial metabolism selectively, to determine whether astroglial disturbances lead to seizures.

Effects of ankle-to-knee external pressures on skin blood perfusion under and distal to compression.

Objective: To compare the effects of select leg compression pressures on blood perfusion in the skin overlying bone and the skin distal to the leg compression.

Design: Blood perfusion of skin overlying the tibia and the foot dorsum was simultaneously measured in 12 healthy subjects using laser Doppler. Each subject's calf was compressed from ankle to knee with an air cast that applied external pressure, ranging from 0 to 40 mm Hg in 10 mm Hg increments.

Lymphedema, lipedema, and the open wound: the role of compression therapy.

As the science of wound healing has evolved over the past two decades, so has awareness of the "hidden epidemic" of lymphedema. Substantial information has been accumulated regarding the pathophysiology and therapy of lymphedema. Until recently, the relationship between wound healing and the negative effects of associated peri-wound lymphedema has received little attention.

Effects of support surface relief pressures on heel skin blood perfusion.

Objective: To investigate the effect of pressure-relief magnitude on heel blood flow.

Design: 12 healthy subjects (5 male, 7 female; 21 to 43 years of age) lay on a support surface for 50 minutes with 1 heel on the end cell of the support surface. Cell pressure was computer controlled to vary cyclically at 5-minute intervals between a constant 20 mm Hg during loading and 10, 5, and 0 mm Hg during off-loading.

A functional androgen receptor is not sufficient to allow estradiol to protect bone after gonadectomy in estradiol receptor-deficient mice.

Although the role of estradiol in maintaining bone mass is well established, the relative contributions of the estradiol receptors ERalpha and ERbeta and of the androgen receptor (AR) remain controversial. To determine the role of ERalpha-mediated, ERbeta-mediated, and non-ER-mediated mechanisms in maintaining bone mass, gonadectomy and estradiol treatment were studied in ER-knockout mice. Estradiol treatment of ovariectomized ERalphabeta(-/-) mice failed to prevent bone loss, precluding significant effects of estradiol on bone through non-ER-signaling pathways.

Assessment of limb volume by manual and automated methods in patients with limb edema or lymphedema.

Objective: Limb edema and lymphedema due to chronic venous insufficiency or mastectomy and radiotherapy negatively effects patient well-being, lifestyle, tissue blood flow, oxygenation, and wound healing. Assessment of the efficacy of volume reduction therapy requires adequate estimation of progressive limb-segment volume changes, which are usually done manually with a tape measure. This study investigated the possibility that an optoelectronic automated method--a potentially less time-consuming and less operator-dependent method--might provide adequate limb volume assessment.

An ethyl-nitrosourea-induced point mutation in phex causes exon skipping, x-linked hypophosphatemia, and rickets.

We describe the clinical, genetic, biochemical, and molecular characterization of a mouse that arose in the first generation (G(1)) of a random mutagenesis screen with the chemical mutagen ethyl-nitrosourea. The mouse was observed to have skeletal abnormalities inherited with an X-linked dominant pattern of inheritance. The causative mutation, named Skeletal abnormality 1 (Ska1), was shown to be a single base pair mutation in a splice donor site immediately following exon 8 of the Phex (phosphate-regulating gene with homologies to endopeptidases located on the X-chromosome) gene.

The increased bone mass in deltaFosB transgenic mice is independent of circulating leptin levels.

Transgenic mice overexpressing deltaFosB, a naturally occurring splice variant of FosB, develop an osteosclerotic phenotype. The increased bone formation has been shown to be due, at least in part, to autonomous effects of deltaFosB isoforms on cells of the osteoblast lineage. However, abdominal fat and marrow adipocytes are also markedly decreased in deltaFosB mice, leading to low serum leptin levels.

Osteoprotegerin reduces osteoclast numbers and prevents bone erosion in collagen-induced arthritis.

Rheumatoid arthritis is characterized by progressive synovial inflammation and joint destruction. While matrix metalloproteinases (MMPs) are implicated in the erosion of unmineralized cartilage, bone destruction involves osteoclasts, the specialized cells that resorb calcified bone matrix. RANK ligand (RANKL) expressed by stromal cells and T cells, and its cognate receptor, RANK, were identified as a critical ligand-receptor pair for osteoclast differentiation and survival.