Large magnetodielectric coupling in the vicinity of metamagnetic transition in 6H-perovskite Ba3GdRu2O9.

The 6H-perovskites Ba3RRu2O9(R = rare earth element) demonstrate the magnetodielectric (MD) coupling as a manifestation of 4d-4fmagnetic interactions. Here, a detailed study of the structural, magnetic, heat capacity, and MD properties of the 6H-perovskite Ba3GdRu2O9is reported. The signature of long-range antiferromagnetic (AFM) ordering ∼14.8 K (TN) is evident from the magnetization and heat capacity studies. TheTNshifts towards the lower temperature side, apart from splitting in two with the application of the magnetic field. Field-dependent magnetization at 2 K shows three metamagnetic transitions with the opening of small hysteresis in different regions. A new transition atT1emerges after the onset of the first metamagnetic transition. Complex magnetic behavior is observed in different magnetic field regions whereas these field regions themselves vary with the temperature. Dielectric response recorded at zero and 80 kOe field exhibits the development of MD coupling well aboveTN. The MD coupling (∼4.5% at 10 K) is enhanced by 25% as compared to the Dy counterpart. Effect of complex magnetic behavior is also conveyed in the MD results where the maximum value of MD coupling is observed in the vicinity of 10 K (onset ofT1) and near the second metamagnetic transition. Our investigation suggests that both Gd and Ru moments align simultaneously atTN. Short-range magnetic ordering is possibly responsible for MD coupling aboveTN.

Structure driven magnetic correlations and magnetodielectric coupling in 6H-perovskite Ba3DyRu2O9.

The 6H-perovskites Ba3(R/M)Ru2O9(R= rare Earth,M= transition metal) exhibit complex magnetism and have been extensively studied recently for their magnetodielectric (MD) properties. Here, we present a detailed study of structural, magnetic, thermodynamic and MD properties of a 6H-perovskite Ba3DyRu2O9. This compound is found to undergo long range antiferromagnetic ordering below ∼5.8 K (TN), along with the presence of metamagnetic transition at low temperatures. The heat capacity shows two additional anomalies at ∼28 K (T1) and ∼33 K (T2), besides the anomaly atTN. Signature of these anomalies is also visible in the derivative of magnetization curve. The dielectric response also shows weak anomalies aroundT1andT2at zero field whereas anomaly atT2gets suppressed at 80 kOe. The observed MD coupling of ∼2%-4% at 80 kOe field below ∼30 K temperature range, is among the highest values observed for the compounds of this family. Low temperature crystal structures of the compound show sharp distortion of Ru2O9octahedra nearT2. Our study points toward the emergence of structurally driven spin correlations of Ru moments resulting in the observed MD coupling in this compound.

Development of an in vitro oviduct epithelial explants model for studying sperm-oviduct binding in the buffalo.

In this study, we developed an in vitro model for studying sperm-oviduct binding in the buffalo. Oviduct explants were prepared by overnight culture of epithelial cells in TCM-199 medium under 5% CO2 at 38.5 °C. Cryopreserved spermatozoa from buffalo bulls (n = 4) were incubated with the oviduct explants, and the sperm-oviduct explants complex was stained with JC-1. The effect of sperm concentration (2, 3 and 4 million), size of the oviduct explants (<0.2, 0.2-0.3, 0.3-0.4 and >0.4 mm2 ) and time of incubation (1 hr and 4 hr) on binding index (BI-number of sperm bound to unit area of explants) was studied. No significant difference was observed in the BI among <0.2, 0.2-0.3 and 0.3-0.4 mm2 size of explants; however, the BI decreased significantly (p < .05) when the size of explants exceeded 0.4 mm2 . The BI decreased significantly (p < .05) when the sperm concentration was increased to 4 million, while the duration of incubation did not have any significant effect on the BI. The interaction of bulls with explants size, sperm concentration and incubation time was not significant. The developed assay has the potential to be used as an in vitro model for studying sperm-oviduct binding in the buffalo.

Age-related changes in transcriptional abundance and circulating levels of anti-Mullerian hormone and Sertoli cell count in crossbred and Zebu bovine males.

Age-related changes in peripheral anti-Mullerian hormone (AMH) concentrations and transcriptional abundance of AMH gene in testicular tissue were studied in crossbred (Holstein Friesian × Tharparkar) and Zebu (Tharparkar) males. In both the breeds, basal AMH concentrations were estimated using ELISA method in blood plasma obtained from six males each at 1, 6, 12, 18, and 24 months age. After blood collection at respective ages, all the males were castrated and expression and immunolocalization of AMH was performed in the testicular tissue. The concentration of AMH in blood plasma was found to be highest at 1 month of age in both crossbred and Zebu males, which subsequently decreased with advancing age. Significantly (P < 0.05) lower concentration of AMH was observed in crossbred as compared with Zebu males at 24 months of age. In line with peripheral AMH concentrations, the expression of AMH gene was also higher (P < 0.05) at 1 month of age, which thereafter declined significantly with advancement of age in crossbred males. Furthermore, the expression of AMH gene differed significantly between Zebu and crossbred males at all the age groups studied. Immunolocalization of AMH in testicular tissue also revealed a stronger expression at 1 month age, which gradually decreased till 24 months of age. The true Sertoli cell count was significantly higher in Zebu compared with crossbred males at all age groups studied except at 6 months age. The relationship between Sertoli cell count and circulating AMH concentrations was negative and significant (r = -0.81; P = 0.004). In conclusion, expression of AMH gene in testicular tissue and peripheral blood concentrations of AMH were higher in young compared with adults in both crossbred and Zebu males; however, the transcriptional abundance and circulating levels of AMH were higher in Zebu compared with crossbred males.

Effect of supplementation of taurine or trehalose in extender on immunolocalization of tyrosine phosphoproteins in buffalo and cattle (Karan Fries) cryopreserved spermatozoa.

The present study assessed the effects of incorporation of Taurine or Trehalose in extender on immunolocalization of tyrosine phosphoproteins, Cryocapacitation and other sperm quality parameters (motility, viability and membrane integrity) in post-thawed sperm from Buffalo (Murrah) and Cattle (Karan Fries). Six ejaculates from six individual bulls from both species were chosen at random and split into four aliquots: one aliquot without dilution (fresh sample), another diluted in egg yolk tris-citrate (EYTC) extender and the rest of aliquots with EYTC dilution supplemented with taurine (50 mm) or trehalose (100 mm), respectively, and cryopreserved. Following cryopreservation, semen were thawed and assessed for standard semen quality parameters. Extent of capacitation in cryopreserved spermatozoa was measured by inducing in vitro acrosome reaction followed by dual staining. Immunolocalization of tyrosine phosphoproteins was carried out by immunocytochemistry using primary antibody clone pT-154 (anti-phosphotyrosine antibody) and FITC-conjugated secondary antibody. Immunofluorescent signals were analysed for level of protein tyrosine phosphorylation in spermatozoa. Post-thaw semen evaluation showed supplementation of taurine or trehalose to EYTC extender significantly (p < 0.05) increased motility, viability and membrane integrity of spermatozoa in both species. Percentage of cryocapacitated spermatozoa was significantly (p < 0.05) higher in cattle as compared to buffalo and degree of cryocapacitaion of spermatozoa decreased significantly (p < 0.05) upon supplementation of additives in both the species. It was also found that tyrosine phosphoproteins were localized differentially in fresh and cryopreserved spermatozoa. Supplementation of taurine or trehalose to freezing extender changed the localization of tyrosine phosphoproteins in cryopreserved spermatozoa similar to fresh in both the species. The results obtained clearly indicated that supplementation of taurine or trehalose to EYTC prior to cryopreservation improves Buffalo and Cattle sperm quality in terms of cryocapacitation and immunolocalization of tyrosine phosphoproteins during freezing-thawing process.

Assessment of intracellular Ca2+, cAMP and 1,2-diacylglycerol in cryopreserved buffalo (Bubalus bubalis) spermatozoa on supplementation of taurine and trehalose in the extender.

In mammalian spermatozoa, intracellular calcium plays a major role in sperm functions like motility and capacitation. Cryopreservation-induced modifications to sperm membrane result in an influx of intracellular calcium affecting calcium-dependent intracellular signalling pathways. Intracellular calcium activates adenyl cyclase to produce cAMP that activates phospholipase A(2) (PLA(2) ) and phospholipase C (PLC) generating lysophosphatidyl choline, 1,2-diacylglycerol (DAG) and IP(3) , acting as intracellular secondary messengers required for sperm capacitation. Present study was designed to determine levels of intracellular calcium, cAMP and DAG in fresh and frozen-thawed buffalo spermatozoa cryopreserved in the presence and absence of taurine or trehalose. A total number of nine ejaculates from three randomly chosen buffalo bulls were cryopreserved in Tris-based egg yolk extender and thawed in warm water at 37°C. The cAMP was measured by enzyme immuno assay, and intracellular calcium was quantified using fluorescent dye FURA 2-AM. Total lipid was extracted from spermatozoa, and DAG was estimated using thin layer chromatography followed by spectrophotometric analysis. Intracellular calcium, cAMP and DAG levels in spermatozoa were significantly (p < 0.01) increased following cryopreservation as compared to fresh ejaculate. Addition of taurine or trehalose to the freezing medium significantly decreased (p < 0.01) the levels of intracellular calcium and cAMP in frozen-thawed spermatozoa. 1,2-diacylglycerol content was also decreased significantly (p < 0.01) in spermatozoa cryopreserved in presence of additives. Moreover, significant (p < 0.01) improvement in post-thaw motility, viability and membrane integrity of spermatozoa on addition of taurine or trehalose clearly indicated the reduced level of capacitation-like changes in buffalo spermatozoa.