Myoepithelioma within the carpal tunnel: a case report and review of the literature

Myoepitheliomas of the extremity are rare and usually benign, while a minority display malignant features. This case demonstrates the diagnosis and management of myoepithelioma within the carpal tunnel. Clinical and radiological tumour features were evaluated. Hematoxylin and eosin stained tumour sections were examined, and immunohistochemistry was performed. Histology revealed a nodular mass of epithelioid cells in clusters within a myxoid/chondroid stroma. No mitoses were noted. Cytokeratins, neuron-specific enolase, synaptophysin, glial fibrillary acidic protein, and S100 were positive on immunohistochemistry. A literature review revealed very few prior reports of myoepithelioma in the wrist, and limited data concerning any relationship between recurrence and quality of surgical margins. In this case, wide local excision would have significantly compromised dominant hand function, and therefore a marginal excision was deemed appropriate in the context of bland histological features. Surgical margins noted in future case reports will aid clinical decision making.     

Expression of secreted frizzled related protein 1, a Wnt antagonist, in brain, kidney, and skeleton is dispensable for normal embryonic development

Secreted frizzled related protein-1 (sFRP1), an antagonist of Wnt signaling, regulates cell proliferation, differentiation and apoptosis and negatively regulates bone formation. The spatial and temporal pattern of endogenous sFRP1 expression and loss-of-function were examined in the sFRP1-LacZ knock-in mouse (sFRP1-/-) during embryonic development and post-natal growth. beta-gal activity representing sFRP1 expression is robust in brain, skeleton, kidney, eye, spleen, abdomen, heart and somites in early embryos, but sFRP1 gene inactivation in these tissues did not compromise normal embryonic and post-natal development. Kidney histology revealed increased numbers of glomeruli in KO mice, observed after 5 years of breeding. In the skeleton, we show sFRP1 expression is found in relation to the mineralizing front of bone tissue during skeletal development from E15.5 to birth. Trabecular bone volume and bone mineral density in the sFRP1-/- mouse compared to WT was slightly increased during post-natal growth. Calvarial osteoblasts from newborn sFRP1-/- mice exhibited a 20% increase in cell proliferation and differentiation at the early stages of osteoblast maturation. sFRP1 expression was observed in osteoclasts, but this did not affect osteoclast number or activity. These findings have identified functions for sFRP1 in kidney and bone that are not redundant with other sFRPs. In summary, the absence of major organ abnormalities, the enhanced bone formation and a normal life span with no detection of spontaneous tumors suggests that targeting sFRP1 can be used as a therapeutic strategy for increasing bone mass in metabolic bone disorders or promoting fracture healing by modulating Wnt signaling.     

Nitric oxide production by nurse shark (Ginglymostoma cirratum) and clearnose skate (Raja eglanteria) peripheral blood leucocytes

Reactive nitrogen intermediates, such as nitric oxide (NO), are important immunomodulators in vertebrate immune systems, but have yet to be identified as mediators of host defence in any member of class Chondrichthyes, the cartilaginous fishes. In the present study, production of NO by nurse shark (Ginglymostoma cirratum) peripheral blood leucocytes (PBL) stimulated with bacterial cell wall lipopolysaccharide (LPS) was investigated. PBL were cultured for 24 to 96 h following stimulation with LPS at concentrations ranging from 0 to 25 microg ml(-1), in both serum-supplemented and serum-free culture conditions. Production of NO was measured indirectly using the Griess reaction, with maximal NO production occurring after 72 h using 10% FBS and 10 microg LPS ml(-1). Application of these culture conditions to PBL from another cartilaginous fish (clearnose skate, Raja eglanteria) resulted in a similar NO response. Addition of a specific inhibitor of inducible nitric oxide synthase (iNOS), L-N(6)-(1-iminoethyl)lysine (L-NIL), resulted in a significant decrease in the production of NO by PBL from both species.     

Bone anabolic effects of parathyroid hormone are blunted by deletion of the Wnt antagonist secreted frizzled-related protein-1

Secreted frizzled-related protein (sFRP)-1 is a Wnt antagonist that when deleted in mice leads to increased trabecular bone formation in adult animals after 13 weeks of age. Treatment of mice with parathyroid hormone (PTH) also increases trabecular bone formation, and some of the anabolic actions of this hormone may result from altered expression of Wnt pathway components. To test this hypothesis, we treated +/+ and -/- female sFRP-1 mice with PTH 1-34 for 30 days and measured distal femur trabecular bone parameters by peripheral quantitative computed tomography (pQCT) and high-resolution micro-computed tomography. During the course of the 32-week study, volumetric bone mineral density (vBMD) declined 41% in vehicle-treated +/+ mice, but increased 24% in vehicle-treated -/- animals. At 8 weeks of age when vBMD was not altered by deletion of sFRP-1, treatment of +/+ and -/- mice with PTH increased vBMD by 147 and 163%, respectively. In contrast, at 24 weeks of age when vBMD was 75% higher in -/- mice than in +/+ controls, treatment with PTH increased vBMD 164% in +/+ animals, but only 58% in -/- mice. Furthermore, at 36 weeks of age when vBMD was 117% higher in -/- mice than in +/+ controls, treatment with PTH increased vBMD 74% in +/+ animals, while no increase was observed in -/- mice. At each of these time points, PTH treatment increased vBMD to a similar level in +/+ and -/- mice, and this level declined with age. In addition, at 36 weeks of age, the vBMD level reached by PTH treatment of +/+ mice was the same as that achieved solely by deletion of sFRP-1. These results indicate that loss of sFRP-1 and PTH treatment increase vBMD to a similar extent. Moreover, as the effects of sFRP-1 deletion on vBMD increase, the ability of PTH to enhance vBMD declines suggesting that there are overlapping mechanisms of action.     

Sequences downstream of the erythroid promoter are required for high level expression of the human alpha-spectrin gene

Alpha-spectrin is a membrane protein critical for the flexibility and stability of the erythrocyte. We are attempting to identify and characterize the molecular mechanisms controlling the erythroid-specific expression of the alpha-spectrin gene. Previously, we demonstrated that the core promoter of the human alpha-spectrin gene directed low levels of erythroid-specific expression only in the early stages of erythroid differentiation. We have now identified a region 3' of the core promoter that contains a DNase I hypersensitive site and directs high level, erythroid-specific expression in reporter gene/transfection assays. In vitro DNase I footprinting and electrophoretic mobility shift assays identified two functional GATA-1 sites in this region. Both GATA-1 sites were required for full activity, suggesting that elements binding to each site interact in a combinatorial manner. This region did not demonstrate enhancer activity in any orientation or position relative to either the alpha-spectrin core promoter or the thymidine kinase promoter in reporter gene assays. In vivo studies using chromatin immunoprecipitation assays demonstrated hyperacetylation of this region and occupancy by GATA-1 and CBP (cAMP-response element-binding protein (CREB)-binding protein). These results demonstrate that a region 3' of the alpha-spectrin core promoter contains a GATA-1-dependent positive regulatory element that is required in its proper genomic orientation. This is an excellent candidate region for mutations associated with decreased alpha-spectrin gene expression in patients with hereditary spherocytosis and hereditary pyropoikilocytosis.     

Biochemical studies of isolated glial (muller) cells from the turtle retina

A method has been developed for the preparation of large numbers of glial (Muller) cells from the turtle retina. After proteolytic dissociation of the retina, Muller cells were separated from retinal neurons by velocity sedimentation at unit gravity. Fractions containing >90 percent morphologically identifiable Muller cells were prepared by this procedure. Fractions containing only Muller cells were obtained by drawing selected cells individually into a micropipette under visual observation. Biochemical analyses of isolated Muller cells showed that (a) these cells did not synthesize and accumulate acetylcholine, γ-aminobutyric acid, or catecholamines when incubated with appropriate radioactive precursors; (b) the specific activities of choline acetyltransferase (EC 2.3.1.6), glutamate decarboxylase (EC 4.1.1.15), and tyrosine hydroxylase (EC 1.14.16.2) in these cells were less than 2 percent of those found in the retina; (c) Muller cells, however, contained high activities of transmitter degrading enzymes-acetylcholinesterase (EC 3.1.1.7) and γ-aminobutyrate- transamine (EC 2.6.1.19); and (d) the cells also possessed high levels of two presumably glial-specific-enzymes-glutamine synthetase (EC 6.3.1.2) and carbonic anhydrase (EC 4.2.1.1). These results, together with other findings, suggest that Muller cells are not capable of neurotransmitter syntheses but possess the enzymes necessary for two important roles in the retina: (a) the inactivation of certain transmitters after synaptic transmission by uptake and degradation, and (b) the maintenance of acid-base balance and the provision of a stable microenvironment in the retina by the removal of metabolic products such as carbon dioxide and ammonia.     

Purification and structural analysis of the modulator of the glucocorticoid-receptor complex. Evidence that modulator is a novel phosphoglyceride

Modulator is the low molecular weight heat-stable inhibitor of glucocorticoid-receptor complex activation. We have purified modulator to apparent homogeneity from heated rat liver cytosol. This was accomplished using Sephadex G-15 gel filtration, Dowex 1 anion-exchange chromatography, and preparative silica high-performance liquid chromatography. The modulator preparation was judged to be homogeneous by analytical silica high-performance liquid chromatography, two-dimensional silica thin-layer chromatography, and proton nuclear magnetic resonance spectroscopy. The apparent concentration of modulator in rat liver cytosol is 6.5 microM. The purified modulator inhibits heat activation of the rat liver glucocorticoid-receptor complex and stabilizes the steroid binding ability of the unoccupied rat liver glucocorticoid receptor in a dose-dependent manner. At a concentration of 5-6.5 microM, modulator inhibits receptor activation and stabilizes the unoccupied receptor by 50%. At a concentration of 500-630 microM, sodium molybdate also inhibits receptor activation and stabilizes the unoccupied receptor by 50%. Thus, modulator appears to be the endogenous factor that exogenous sodium molybdate mimics in vitro. Chemical analysis of the purified modulator following two-dimensional silica thin-layer chromatography indicates that modulator is an aminophospholipid. Physical analysis of the purified modulator by infrared and nuclear magnetic resonance spectroscopy, as well as mass spectrometry, demonstrates that modulator is an ether aminophosphoglyceride.