Zirconium, calcium, and strontium contents in magnesium based biodegradable alloys modulate the efficiency of implant-induced osseointegration

Development of new biodegradable implants and devices is necessary to meet the increasing needs of regenerative orthopedic procedures. An important consideration while formulating new implant materials is that they should physicochemically and biologically mimic bone-like properties. In earlier studies, we have developed and characterized magnesium based biodegradable alloys, in particular magnesium-zirconium (Mg-Zr) alloys. Here we have reported the biological properties of four Mg-Zr alloys containing different quantities of strontium or calcium. The alloys were implanted in small cavities made in femur bones of New Zealand White rabbits, and the quantitative and qualitative assessments of newly induced bone tissue were carried out. A total of 30 experimental animals, three for each implant type, were studied, and bone induction was assessed by histological, immunohistochemical and radiological methods; cavities in the femurs with no implants and observed for the same period of time were kept as controls. Our results showed that Mg-Zr alloys containing appropriate quantities of strontium were more efficient in inducing good quality mineralized bone than other alloys. Our results have been discussed in the context of physicochemical and biological properties of the alloys, and they could be very useful in determining the nature of future generations of biodegradable orthopedic implants.

Strontium content and collagen-I coating of magnesium-zirconia-strontium implants influence osteogenesis and bone resorption.

Our objective was to study the role of Collagen type-I (Col-I) coating on Magnesium-Zirconia (Mg-Zr) alloys, containing different quantities of Strontium (Sr), in enhancing the in vitro bioactivity and in vivo bone-forming and mineralisation properties of the implants.

Activation and early parthenogenesis of bovine oocytes treated with ethanol and strontium

Efficient artificial activation is indispensable for the success of cloning programs. Strontium has been shown to effectively activate mouse oocytes for nuclear transfer procedures, however, there is limited information on its use for bovine oocytes. The present study had as objectives: (1) to assess the ability of strontium to induce activation and parthenogenetic development in bovine oocytes of different maturational ages in comparison with ethanol; and (2) to verify whether the combination of both treatments improves activation and parthenogenetic development rates. Bovine oocytes were in vitro matured for 24, 26, 28, and 30 h, and treated with ethanol (E, 7% for 5 min) or strontium chloride (S, 10 mM SrCl2 for 5 h) alone or in combination: ethanol + strontium (ES) and strontium + ethanol (SE). Activated oocytes were cultured in vitro in synthetic oviductal fluid (SOF) medium and assessed for pronuclear formation (15-16 h), cleavage (46-48 h) and development to the blastocyst stage (M). Treatment with ethanol and strontium promoted similar results regarding pronuclear formation (E, 20-66.7%; S, 26.7-53.3%; P > 0.05) and cleavage (E, 12.8-40.6%; S, 16.1-41.9%; P > 0.05), regardless of oocyte age. The actions of both strontium and ethanol were influenced by oocyte age: ethanol induced greater activation rates after 28 and 30 h of maturation (48.4 and 66.7% versus 20.0 and 23.3% for 24 and 26 It, respectively; P < 0.05) and strontium after 30 It (53.3%) was superior to 24 and 26h (26.7% for both). Blastocyst development rates were minimal in all treatments (0.0-6.3%; P > 0.05), however, when the mean (+/-S.D.) cell number in blastocysts at the same maturational period was compared, strontium treatment was superior to ethanol for activation rates (82 +/- 5.7 and 89.5 +/- 7.8 versus 54 and 61, at 28 and 30 h, respectively). Improved results were obtained by combined treatments. The combination of ethanol and strontium resulted in similar pronuclear formation (ES, 36.7-83.9%; SE, 53.1-90.3%) and cleavage rates (ES, 31.3-81.3%; SE, 65.6-80.7%). Regarding embryo development, there was no difference (P > 0.05) between treatments, and blastocysts were only obtained in treatment SE at 24 and 26 h (6.5% for both). It is concluded that, SrCl2 induces activation and parthenogenetic development in bovine oocytes. (C) 2003 Elsevier B.V. All rights reserved.

Parthenogenetic activation of bovine oocytes using single and combined strontium, ionomycin and 6-dimethylaminopurine treatments

In vitro-matured (IVM) bovine oocytes were activated with single and combined treatments of strontium (S), ionomycin (1) and 6-DMAP (D). Using oocytes IVM for 26 h, we observed that activation altered cell cycle kinetics (faster progression, MIII arrest, or direct transition from MII to pronuclear stage) when compared to in vitro fertilization. The effect of oocyte age on early parthenogenesis was assessed in oocytes IVM for 22, 26 and 30 h. Better results in pronuclear development were obtained in treatments ISD (81.7%) at 22 h; D (66.7%), IS (63.3%), ID (73.3%) and ISD (76.7%) at 26 h; and D (86.7%), IS (85.0%) and ID (78.3%) at 30 h. Higher cleavage occurred on ISD (80.0%) at 22 h; ID (83.3%) and ISD (91.7%) at 26 h; and 1 (86.7%), IS (90.0%), ID (85.0%) and ISD (95.0%) at 30 h. More blastocysts were achieved in ID (25.0%) and ISD (18.3%) at 22h; and in ID at 26h (45.0%) and 30h (50.0%). We also observed that IS allowed higher haploid (77.4%) embryonic development, whilst ID was better for diploid (89.1%) development. It was concluded that association of S and D without I was not effective for blastocyst development; treatments using S were less influenced by oocyte age, but when S was associated with D there was a detrimental effect on aged oocytes; treatment ISD promoted higher activation and cleavage rates in young oocytes and ID protocol was the best for producing blastocysts.

Karyoplast exchange between strontium- and 6-DMAP-parthenogenetically activated zygotes of cattle

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Activation of bovine oocytes by strontium combined or not with an electric pulse

O objetivo deste trabalho foi avaliar as taxas de ativação e de clivagem de oócitos bovinos tratados com estrôncio (10mm de SrCl2), após maturação in vitro por 27-28 horas. No experimento 1, os tratamentos foram: S4 - ativação pelo estrôncio por 4 horas; S12 - ativação pelo estrôncio por 12 horas; S30 - ativação pelo estrôncio por 30 horas; e P - ativação por pulso elétrico (3 pulsos de 1,0kv/cm). No experimento 2 os tratamentos foram: PS4 - ativação combinada pelo pulso elétrico e pelo estrôncio por 4 horas; S4P - ativação pelo estrôncio por 4 horas e pelo pulso elétrico; e PS30 - ativação pelo pulso elétrico e pelo estrôncio por 30 horas. No experimento 1, todos os tratamentos apresentaram taxas similares de ativação (83-90%; P>0,05). Para clivagem, P foi melhor (53%; P<0,05) do que todos os tratamentos com estrôncio (6 a 28%). No experimento 2, o tratamento S4P apresentou melhor taxa de ativação (88%; P<0,05) do que PS4 e PS30 (60 e 68%, respectivamente). Para clivagem, observou-se o mesmo padrão, S4P (65%; P<0,05) e PS4 e PS30 (37% e 44%, respectivamente). Conclui-se que o estrôncio é capaz de ativar oócitos bovinos e sua combinação com pulso elétrico não melhora a ativação. Este é o primeiro relato demonstrando que o estrôncio ativa oócitos bovinos.

Luminescent and morphological study of Sr2CeO4 blue phosphor prepared from oxalate precursors

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural characterization and Curie temperature determination of a sodium strontium niobate ferroelectric nanostructured powder

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of strontium and calcium simultaneous substitution on electrical and structural properties of Pb1-x-y Ca (x) Sr (y) TiO3 thin films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of strontium addition on ferroelectric phase transition of PZT thin films prepared by chemical route

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Parthenogenetic development of domestic cat oocytes treated with ionomycin, cycloheximide, roscovitine and strontium

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Barium strontium titanate powders prepared by spray pyrolysis

Ultasonic spray pyrolysis (SP) has been investigated for the production of the barium strontium titanate (BST) powders from the polymeric precursors. The processing parameters, such as flux of aerosol and temperature profile inside the furnace, were optimized to obtain single phase BST. The powders were characterized by the methods of X-ray diffraction analysis, SEM, EDS and TEM. The obtained powders were submicronic, consisting of spherical, polycrystalline particles, with internal nanocrystalline structure. Crystallite size of 10 nut, calculated using Rietveld refinement, is in a good agreement with results of HRTEM. (c) 2005 Elsevier B.V. All rights reserved.