1,721,030 research outputs found
The Ca2+ overload hypothesis in the familial form of Alzheimer's disease: New light from presenilin 2 mutations.
No full textBackground: The presenilin 2 (PS2) mutation M239I is associated with late onset and relatively mild progression of Familial Alzheimer Disease (FAD) (1). In fibroblasts of FAD patients carrying this PS2 mutation, and in cell lines (HeLa and HEK293) both transiently and stably transfected with the cDNA for PS2-M239I, Ca2+ release in response to application of the SERCA inhibitor cyclopiazonic acid is significantly reduced compared to the corresponding controls (fibroblasts from age-matched, healthy individuals and non transfected cell lines, respectively). In addition, the capacitative Ca2+ influx (CCE), that is associated with store depletion, showed a tendency to a reduction, however not significant (2). Objective: In this study we aim at establishing whether other FAD-linked PS2 mutations (N141I and T122R) induce a similar dysregulation of Ca2+ homeostasis. Methods: By means of different techniques, such as the fluorescent probe fura-2, and the cytosolic or ER-targeted aequorins, that allow to measure the Ca2+ concentration of the cytosol and the endoplasmic reticulum (ER), we analyzed how Ca2+ is handled by human fibroblasts from FAD patients carrying the PS2-T122R mutation and by different cell lines either stably or transiently expressing the same PS2 mutant or the PS2-N141I. Results: Preliminary data suggest that also these two other PS2 mutants significantly reduce the ER Ca2+ content and cause a mild reduction of CCE. The molecular target(s) through which these FAD-associated PS2 mutants exert their effect is under investigation. Conclusions: Our findings confirm that Ca2+ dysregulation is linked to FAD but contrast with the general idea that mutant presenilins cause an ER “Ca2+ overload”. We are therefore testing with the same previously described approach, also three FAD-associated PS1 mutations (M146L, A246E, L286V) together with the loss of function mutation PS1-D257A. Differences in onset and progression of the disease have been reported between FAD-linked PS1 and PS2 mutants suggesting the possibility that opposite effects on Ca2+ handling by mutant PS1 and PS2 may impact on APP processing, Ab42 release and neuronal survival.
1. Finckh U. et al. (2000) Neurology 23:2006-8.
2. Zatti G. et al. (2004) Neurobiol. Disease (in press
Familial Alzheimerâ€TMs Disease presenilin mutants reduce calcium levels of intracellular stores. A critical revaluation of the “calcium overload†hypothesis
No full textBackground: Presenilin-1 and -2 (PS1 and PS2) mutations, the major cause of Familial Alzheimer’s Disease (FAD), have been causally implicated in the pathogenesis of neuronal cell death through a perturbation of cellular Ca2+ homeostasis. We have recently shown that, at variance with previous suggestions obtained in cells expressing other FAD-linked PS mutations, PS2-M239I and PS2-T122R cause a reduction and not an increase in cytosolic Ca2+ rises induced by Ca2+ release from stores (1,2). Objective(s): In this study we aim at investigating whether other FAD-linked PS mutations induce a similar dysregulation of Ca2+ homeostasis. Methods: Different cell models have been used: human fibroblasts from controls and FAD patients, cell lines (SH-SY5Y, HeLa, HEK293, MEFs) and rat primary neurons expressing a number of PS mutations, e.g. P117L, M146L, L286V, and A246E in PS1 and M239I, T122R, and N141I in PS2. The effects of FAD-linked PS mutations on cytosolic Ca2+ changes have been monitored either by using fura-2 or recombinant cytosolic aequorin as the probe. Results: Independently of the cell model or the employed probe, the cytosolic Ca2+ increases, caused by agonist stimulation or full store depletion by drug treatment, were reduced or unchanged in cells expressing the PS mutations. Using aequorins, targeted to the endoplasmic reticulum or the Golgi apparatus, we here show that FAD-linked PS mutants lower the Ca2+ content of intracellular stores. The phenomenon was most prominent in cells expressing PS2 mutants, and was observed also in cells expressing the non-pathogenic, “loss-of-function” PS2-D366A mutation. Conclusions: Taken as a whole, our findings, while confirming the capability of presenilins to modify Ca2+ homeostasis, suggest a re-evaluation of the “Ca2+ hypothesis” in AD and a new working hypothesis is presented.
1. Zatti G, Ghidoni R, Barbiero L, Binetti G, Pozzan T, Fasolato C, Pizzo P. (2004). Neurobiology of disease, 15, 269-278.
2. Giacomello M, Barbiero L, Zatti G, Squitti R, Binetti G, Pozzan T, Fasolato C, Ghidoni R, Pizzo P. (2005). Neurobiology of disease, 18, 638-648
Complex fractures of the femur: treatment with a long gamma nail: short- and medium-term experience
No full textThe introduction of the gamma nail and of the long gamma nail, associating the principle of intramedullary nailing and of the sliding screw-plate, has led to good results in the treatment of complex fractures such as per-sub-trochanteric fractures and associated fractures of the femoral neck-diaphysis. In this study, our experience with the long gamma nail (Long Gamma Nail Howmedica) is presented. Of the 43 patients treated between 1993 and 1998, 21 (49%) with a mean follow-up of 2.5 years (1-5 years) were reviewed. Clinical and a radiographic evaluations were obtained for each of the patients. This study showed that there was a high incidence of poor consolidation (dysmetria in 10 patients, torsion deficit in 7, consolidation in varus of the femoral neck in 1 patient) particularly in associated fractures of the femoral neck and diaphysis, accompanied, however, by good functional recovery (only 3 patients with modification in the angle of progression of the foot) and by the satisfaction of the patients questioned. Thus, indications for the use of this device in proximal fractures of the femur, particularly in elderly patients and in high-energy traumas, are demonstrated
Reduction of Ca2+ stores and capacitative Ca2+ entry is associated with the familial Alzheimer's disease presenilin-2 T122R mutation and anticipates the onset of dementia
Full text linkMutations in the presenilin genes PS1 and PS2, the major cause of familial Alzheimer's disease (FAD), are associated with alterations in Ca2+ signalling. In contrast to the majority of FAD-linked PS1 mutations, which cause an overload of intracellular Ca2+ pools, the FAD-linked PS2 mutation M239I reduces Ca2+ release from intracellular stores [Zatti, G., Ghidoni, R., Barbiero, L., Binetti, G., Pozzan, T., Fasolato, C., Pizzo, P., 2004. The presenilin 2 M239I mutation associated with Familial Alzheimer's Disease reduces Ca2+ release from intracellular stores. Neurobiol. Dis. 15/2, 269-278]. We here show that in human FAD fibroblasts another PS2 mutation (T122R) reduces both Ca2+ release and capacitative Ca2+ entry. The observation, done in two monozygotic twins, is of note since only one of the subjects showed overt signs of disease at the time of biopsy whereas the other one developed the disease 3 years later. This finding indicates that Ca2+ dysregulation anticipates the onset of dementia. A similar Ca2+ alteration occurred in HeLa and HEK293 cells transiently expressing PS2-T122R. Based on these data, the "Ca2+ overload" hypothesis in AD pathogenesis is here discussed and reformulated
Reversibility of the inhibitory effect of salmon calcitonin on bone resorption in rats.
No full textInhibition of osteoclastic bone resorption has been induced in growing rats with high doses of salmon calcitonin. This effect was evaluated by measuring the perichondrial ring height of the proximal tibial metaphysis. The aim was to assess whether osteoclastic activity resumed after a period of inhibition with high doses of calcitonin. 20 male Sprague-Dawley rats were treated for 21 days with 100 units/kg/day of salmon calcitonin subcutaneously and killed after 0-60 days, together with non-treated controls at 0 and 60 days. Arrest of metaphyseal modeling and increased height of the perichondrial ring at the end of the period of therapy (P 0.002 versus controls) were observed. Recovery of bone resorption was evident 20 and 40 days after withdrawal of calcitonin
Histology of metal-bone interface: Considerations about interpretation of plastic embedded slides.
No full textThe interference of processing and preparation of histological slides for the study of morphology and morphometry of bone-implant interfaces was investigated in an experimental model, in which a titanium plate was inserted through the cortical bone into the medullary cavity of rat tibiae. The thickness of the sections, burr and notching of the cut border, and staining properties of the embedding resin were found to significantly influence the appearance of the bone-implant interface and, when morphometry was applied, the extent of direct bone-metal contact. The model of the interface resulting from this study is that of some bony processes abutting on the metal surface, while most of the contact is between metal and connective tissue or vascular spaces
Experimental osteoporosis in the rat induced by a hypocalcic diet.
No full textThe administration of a diet deficient in calcium in the rat quickly produces a reduction in the skeletal mass, with narrowing of the diaphyseal cortex, and less density of the metaphysis. The bone mineral content, determined by a double ray photonic mineralometer, is significantly lower as compared to controls, while histological examination does not reveal defects in calcification. The pathogenetic mechanism is characterised by stimulation of the parathyroid glands in response to a decrease in plasma calcium determined by the insufficient diet. We observed a bone response in two phases: the first, with elevated velocity of remodelling and prevalence of osteoclastic resorption despite the presence of intense osteoblastic activity; the second, with reduced bone remodelling (except for the metaphyseal area). Although these observations do not imply that human osteoporosis involves the same pathogenetic mechanism, it appears possible to use this experimental model to study the effects of endocrine and pharmacological factors on the activity of bone remodelling, which also in human osteoporosis is characterised by the prevalence of osteoclastic resorption
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