Increase Of Gd3 Research Articles

Influence of Rare Earth (Gd3+) on Structural, Gigahertz Dielectric and Magnetic Studies of Cobalt ferrite

A series of Gd3+ doped nanocrystalline Co-ferrites CoGdxFe2-xO4 (x = 0.0 to 0.1) has been prepared by sol-gel auto combustion technique. Structural and morphology studies were performed using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Indexed XRD patterns confirm the formation of pure cubic spinel phase. Average crystallite sizes ranges from 16 nm to 25 nm ±2, were calculated from Sherrer's formula and Williamson Hall plots. Crystal strain increases with increase in doping amount of trivalent Gd ion. Lattice constant (a) and crystallite size D (311) increases with increase in Gd3+ concentration due to large ionic radii (0.94nm) of Gd3+ replacing Fe3+ (0.64nm). SEM images show the spherical morphology and uniform size distribution. Room temperature DC electrical resistivity decreases (~106) for x=0.025 then increases up to x=0.1 ~ (4.5×107). Dielectric properties have been studied using RF Impedance/material analyzer in the frequency range of 1 MHz to 1GHz. All the studied samples show a semi-conducting behavior as Permittivity and tangent loss (tanδ) decreases with the substitution of Gd3+ in parent crystal structure and have values of 4.92 and 0.016 at 1 GHz respectively. Complex impedance and Complex electric modulus plots were further studied for complete contribution of grains and grain boundary resistances to conduction and resonance frequencies respectively. Magnetic studies by Vibrating Sample Magnetometer (VSM) shows that magnetization (Ms) decreases with increase in Gd3+ concentration from 63 emu/gm to 27.26 emu/gm. Coercivity (Hc) first decreases for x=0.025, after which it increases to 2308 Oe for x=0.1.

Gd[formula omitted] substituted of Mn[formula omitted]Zn[formula omitted]Gd[formula omitted]Fe[formula omitted]O[formula omitted] ([formula omitted], 0.2, 0.3, 0.4) ferrites for ferrofluids application

Gd3+ substituted MnZn ferrites [ Mn0.5Zn0.5GdxFe2−xO4 (x=0.1, 0.2, 0.3, 0.4)] nanoparticles have been explored for ferrofluid applications. The oleic acid coated water base ferrofluids of these ferrites are prepared by chemical co-precipitation. The effect of Gd3+ ions on structural morphological and magnetic properties of these samples are characterized by X-ray diffraction, FTIR, EPR and dc magnetization techniques. The crystallite size, particle size and saturation magnetization increases with the increase of Gd3+ ions concentration while lattice parameter and lattice strain reduces. The g-value, peak-to-peak linewidth and spin concentration evaluated from EPR spectra correlated with cations occupancy.

Nanocrystalline Nd2–yGdyZr2O7 pyrochlore: Facile synthesis and electrical characterization

Three solid solutions of pyrochlores in the series Nd2-yearsGdyZr2O7 (y = 0.8, 1.0, 1.2) were synthesized by the gel combustion method using citric acid as fuel. This results in a soft agglomerate powder as verified by dynamic light scattering. The single-phase nature of the products has been confirmed by x-ray diffraction. The increase in full width at half-maxima in the Raman spectra with an increase in Gd3+ content indicates that disorder increases with Gd3+ content. The morphology and particle size of the products were investigated by transmission electron microscopy. Scanning electron microscopy study reveals that the sintered pellets have a density higher than 92% of theoretical densities. The total ionic conductivity measurements in the temperature range 375–800 °C show that with the increase of disorder (Gd3+ content) in the system the activation energy of conduction increases from 0.98 to 1.06 eV and the preexponential factor, which is proportional to the number of mobile species, also follow the same trend of increase. The total conductivity measured in reducing atmosphere shows no change in electrical conductivity, which verifies a negligible contribution of electronic contribution in this system.

Gangliosides are involved in neural differentiation of human dental pulp-derived stem cells

Human dental pulp-derived stem cells (hDPSCs) have been considered alternative sources of adult stem cells because of their potential to differentiate into multiple cell lineages. This study investigated the possible role of gangliosides in the neural differentiation of hDPSCs. When hDPSCs were cultured under neural differentiation conditions, expression of neural cell marker genes such as Nestin, MAP-2, and NeuN was detected. Immunostaining and high-performance thin-layer chromatography analysis showed that an increase in ganglioside biosynthesis was associated with neural differentiation of hDPSCs. Specifically, a significant increase in GD3 and GD1a expression was observed during neural differentiation. To confirm the role of gangliosides in neural differentiation, ganglioside biosynthesis was inhibited in hDPSCs by knockdown of UDP-glucose ceramide glucosyltransferase ( Ugcg), which prevented differentiation into neural cells. These results suggest that gangliosides may play a role in the neural differentiation process of hDPSCs.

Dietary Ganglioside and Long-Chain Polyunsaturated Fatty Acids Increase Ganglioside GD3 Content and Alter the Phospholipid Profile in Neonatal Rat Retina

During early development, the ganglioside composition of the retina changes significantly, in that GD3 becomes the primary ganglioside in the mammalian retina. Because gangliosides play an important role in neuronal cell differentiation and proliferation, this change in ganglioside profile may indicate retinal maturation. Dietary long-chain polyunsaturated fatty acids (LCPs) such as 20:4n-6 and 22:6n-3 improve visual acuity in infants. Dietary LCPs stimulate neonatal retinal development by altering membrane phospholipids, which in turn affect cell signaling pathways. It is unknown whether dietary ganglioside and LCPs affect the metabolism of phospholipids and gangliosides during retinal development. Male Sprague-Dawley rats (18 days old) were fed semipurified diets consisting of 20% fat (control diet) for 2 weeks containing either 0.1% ganglioside enriched in GD3 (GG diet) or 1% 20:4n-6 and 0.5% 22:6n-3 (LCP diet) in the control diet. The profile of ganglioside and phospholipid was measured. The GG diet increased the ganglioside content by 39% in the retina, with a relative increase in GD3 (by 13%). Dietary LCPs significantly increased the relative levels of GD3 (by 19%, P < 0.01). Total phospholipid was decreased by the LCP-supplemented diet (by 28%). Phosphatidylcholine and phosphatidylserine increased with concomitant decreases in phosphatidylinositol and lyso-phosphatidylethanolamine when animals were fed either the LCP or the GG diet. Animals fed dietary ganglioside increased in total retinal ganglioside and GD3 content during retinal development, with a concomitant alteration of phospholipid metabolism. Feeding animals dietary LCPs also affected ganglioside metabolism in the developing retina, suggesting a new mechanism by which these dietary lipids may promote maturation of photoreceptor cells.

Dietary ganglioside decreases cholesterol content, caveolin expression and inflammatory mediators in rat intestinal microdomains

Membrane microdomains rich in cholesterol and sphingolipids, including gangliosides (GGs), are known to be important regions for cell signaling and binding sites for various pathogens. Cholesterol depletion inhibits the cellular entry of pathogens and also reduces inflammatory signals by disrupting microdomain structure. Our previous study showed that dietary gangliosides increased total ganglioside incorporation while decreasing cholesterol in the intestinal mucosa. We hypothesized that diet-induced reduction in cholesterol content in the intestinal mucosa disrupts microdomain structure resulting in reduced pro-inflammatory signals. Male weanling Sprague-Dawley rats were fed semipurified diets for 2 weeks. Experimental diets were formulated to include either ganglioside-enriched lipid (GG diet, 0.02% gangliosides [w/w of diet] ) or polyunsaturated fatty acid (PUFA diet, 1% arachidonic acid and 0.5% docosahexaenoic acid, w/w of total fat), in a control diet containing 20% fat. Levels of cholesterol, GG, caveolin, platelet activating factor (PAF), and diglyceride (DG) were measured in the microdomain isolated from the intestinal brush border. The GG diet increased total gangliosides by 50% with a relative increase in GD3 and a relative decrease in GM3. Cholesterol content was also reduced by 23% in the intestinal microdomain. These changes resulted in a significant decrease in the ratio of cholesterol to ganglioside. The GG diet and the PUFA diet were both associated with reduction in caveolin, PAF, and DG content in microdomains, whereas no change occurred in the ganglioside profile of animals fed the PUFA diet. Dietary gangliosides decrease the cholesterol/ganglioside ratio, caveolin, PAF and DG content in microdomains thus exerting a potential anti-inflammatory effect during gut development.

Magnetic and optical properties and electron paramagnetic resonance of gadolinium-containingoxide glasses

Magnetic susceptibility, electron paramagnetic resonance (EPR)and optical absorption have been studied in a glass system20La2O3–22Al2O3–23B2O3–35(SiO2+GeO2) with apart of La2O3 substituted by Gd2O3 in different concentrations. Positive Weiss constants have beenfound in more heavily doped glasses and ascribed to clustering ofGd3+ ions.Computer simulations of the EPR spectra show that the short-range ordering in the environment ofthe Gd3+ ions is well preserved. The relative distribution widths of the ligand coordinates are lessthan 2%. In the more heavily doped glasses the EPR spectra are superpositionsof signals arising from isolated ions and ferromagnetic clusters. The increase ofGd3+ concentration is shown to change substantially the strong optical absorption edgewhile only small changes of f–f absorption band characteristics are observed. Thisdifference is associated with the different effect of the Gd ion clustering on themechanisms of the strong absorption in the ultraviolet region and the f–f absorption.

An early increase in the disialoganglioside GD3 contributes to the development of neuronal apoptosis in culture

We induced apoptosis in primary cultures of cerebellar granule neurons by switching the growing medium into a medium containing lower concentrations of K(+) (5 or 10 mM instead of 25 mM) or, alternatively, by addition of staurosporine. The apoptotic phenotype was always preceded by an early increase in the intracellular levels of the disialoganglioside GD3, which peaked at 2-6 h and returned back to normal at 12 h. GD3 synthase, the enzyme that forms GD3 from the monosialoganglioside GM3, was also induced at early times after the induction of apoptosis in granule cells. Immunofluorescent staining showed that GD3 increased in neuronal cell bodies and neurites, but was never localized in cell nuclei. In cultures switched into a low K(+)-containing medium, exogenously applied GD3, but not the disialoganglioside GD1a, accelerated the development of neuronal apoptosis. In contrast, the antisense-induced knock-down of GD3 synthase was protective against granule cell death induced by lowering extracellular K(+) from 25 to 10 - but not 5 - mM. These results demonstrate that an early and transient increase in GD3 synthesis is one of the factors that contribute to the induction of neuronal apoptosis in culture.

Beta-amyloid-induced synthesis of the ganglioside GD3 is a requisite for cell cycle reactivation and apoptosis in neurons.

We have shown that cortical neurons challenged with toxic concentrations of beta-amyloid peptide (betaAP) enter the S phase of the cell cycle before apoptotic death. Searching for a signaling molecule that lies at the border between cell proliferation and apoptotic death, we focused on the disialoganglioside GD3. Exposure of rat cultured cortical neurons to 25 microm betaAP(25-35) induced a substantial increase in the intracellular levels of GD3 after 4 hr, a time that precedes neuronal entry into S phase. GD3 levels decreased but still remained higher than in the control cultures after 16 hr of exposure to betaAP(25-35). Confocal microscopy analysis showed that the GD3 synthesized in response to betaAP colocalized with nuclear chromatin. The increase in GD3 was associated with a reduction of sphingomyelin (the main source of the ganglioside precursor ceramide) and with the induction of alpha-2,8-sialyltransferase (GD3 synthase), the enzyme that forms GD3 from the monosialoganglioside GM3. A causal relationship between GD3, cell-cycle activation, and apoptosis was demonstrated by treating the cultures with antisense oligonucleotides directed against GD3 synthase. This treatment, which reduced betaAP(25-35)-stimulated GD3 formation by approximately 50%, abolished the neuronal entry into the S phase and was protective against betaAP(25-35)-induced apoptosis.

β-Amyloid-Induced Synthesis of the Ganglioside Gd3 Is a Requisite for Cell Cycle Reactivation and Apoptosis in Neurons

We have shown that cortical neurons challenged with toxic concentrations of β-amyloid peptide (βAP) enter the S phase of the cell cycle before apoptotic death. Searching for a signaling molecule that lies at the border between cell proliferation and apoptotic death, we focused on the disialoganglioside GD3. Exposure of rat cultured cortical neurons to 25 μmβAP(25–35) induced a substantial increase in the intracellular levels of GD3 after 4 hr, a time that precedes neuronal entry into S phase. GD3 levels decreased but still remained higher than in the control cultures after 16 hr of exposure to βAP(25–35). Confocal microscopy analysis showed that the GD3 synthesized in response to βAP colocalized with nuclear chromatin. The increase in GD3 was associated with a reduction of sphingomyelin (the main source of the ganglioside precursor ceramide) and with the induction of α-2,8-sialyltransferase (GD3 synthase), the enzyme that forms GD3 from the monosialoganglioside GM3. A causal relationship between GD3, cell-cycle activation, and apoptosis was demonstrated by treating the cultures with antisense oligonucleotides directed against GD3 synthase. This treatment, which reduced βAP(25–35)-stimulated GD3 formation by ∼50%, abolished the neuronal entry into the S phase and was protective against βAP(25–35)-induced apoptosis.

Changes of the ganglioside pattern and content in human fibroblasts by high density cell population subculture progression.

In this study we show that the ganglioside content and pattern of human skin fibroblasts change along the process of cell subculture progression by varying the cell density. GM3, GD3 and GD1a were components of the total cell ganglioside mixtures extracted from cells, but GD1a was in all the extracts a minor component or very scant. Other gangliosides present in traces were not characterised. The fibroblast ganglioside content of 52 pools of cells obtained from 5 different cell lines cultured at variable cell density ranged from 2.0 to 13.1 nmoles per mg of cell protein. The molar ratio between GM3 and GD3 varied from 418 to 0.6 in the ganglioside mixtures, as determined by densitometric quantitative analysis after thin layer chromatographic separation. Both the ganglioside content and the GM3/GD3 molar ratio were constant along several passages of subculture progression performed by plating cells collected at confluence. Instead, when the subculture progression was performed by plating cells collected at a few days after reaching confluence, a progressive increase of the ganglioside content was observed. GD3 increased proportionally more than GM3 so that a progressive decrease of the ratio between GM3 and GD3 was observed. In some experiments, GD3 was very scant at the beginning of the progression, while it was near 30% after 5 passages under these conditions. The progressive increase of GD3 along the high density cell population subculture progression was associated to a moderate increase of the mRNA GD3 synthase.

Ganglioside profiles in human gliomas: quantification by microbore high performance liquid chromatography and correlation to histomorphology and grading.

The composition and the content of gangliosides changes during physiological growth and differentiation as well as in neoplastic cell transformation. In order to determine if ganglioside profiles correlate with brain tumour malignancy, the ganglioside distribution was determined in 31 gliomas of astrocytic origin and in non-tumour tissue by a recently developed microbore high performance liquid chromatography (HPLC) method. Glioma malignancy was graded according to the grading system proposed by the World Health Organization (WHO) in 1993. In general, an increase of GD3 and a decrease of normal brain gangliosides correlated with a higher grade of malignancy. Pilocytic astrocytomas Grade I had a distinctive ganglioside profile, histologically as well as biochemically. Although they are low-grade gliomas, the pilocytic astrocytomas exhibited a GD3 content comparable to anaplastic gliomas and could only be biochemically distinguished from other tumour grades by relatively high type "b" ganglioside levels. Thus, ganglioside composition not only reflects anaplasia but can also be used to indicate biological characteristics of tumours of different histogenetic origin.

In human fetal astrocytes exposure to interleukin-1 beta stimulates acquisition of the GD3+ phenotype and inhibits cell division.

In human astrocyte cultures established from second-trimester fetal brain tissue, approximately 5-10% of total astrocyte population in unstimulated cultures were GD3+/glial fibrillary acidic protein (GFAP)+. The GD3+ cells were always GFAP+ and grew as flat, highly spread cells but changed to process-bearing cells after interleukin-1 beta (IL-1 beta) stimulation. It is interesting that IL-1 beta, a known mitogen for rat astrocytes, suppressed human fetal astrocyte proliferation as determined by [3H]thymidine incorporation, bromodeoxyuridine (BrdU) labeling, and cell counting. The GD3+ population, however, consistently increased in absolute number after IL-1 beta stimulation, in a dose- and time-dependent manner. The IL-1 beta-mediated increase in number of GD3+ astrocytes was independent of initial cell density or serum concentration. By flow cytometry, IL-1 beta enhanced both the mean fluorescence intensity and the percentage of GD3+ cells. To investigate whether the increase in GD3+ astrocyte cell number was due to proliferation of preexisting GD3+ astrocytes or due to conversion of GD3- to GD3+ cells, we performed BrdU/GD3 double immunocytochemistry. BrdU/GD3 double-positive cells were extremely rare in both control and IL-1 beta-stimulated cultures. Moreover, an increase in number of GD3+ astrocytes was still observed in control and IL-1 beta-stimulated cultures were GD3+ cells had been initially eliminated by cell sorting. These results indicate that GD3+ astrocytes in human fetal culture may represent a postmitotic, differentiated, distinct phenotype.

Interleukin 4 enhances ganglioside GD3 expression on the human fibroblast cell line WI-38.

Human fibroblast cell line WI-38 cultured in vitro was treated with a human recombinant IL-4 at concentrations of 1 to 100 U/ml to examine the alteration of glycosphingolipid (GSL) expression of the cells. Neutral GSL of non-treated WI-38 cells consisted of CMH (GlcCer), CDH, CTH, and Gb4Cer; CMH and CTH were the major components. The acidic GSL were composed of GM3 as the predominant component and other minor gangliosides including GD3. The neutral GSLs did not change in profile during the treatment with IL-4, while the acidic GSLs showed a prominent change, an increase of GD3 content. The increase of GD3 was detectable with IL-4 concentrations over 1 U/ml, and reached a plateau at 10 U/ml, where the amount of GD3 was almost equal to that of GM3. The GD3 increase occurred at 24 h after the IL-4 treatment, and lasted for at least 96 h, as long as IL-4 remained present in the culture media. The GD3 synthase (sialyltransferase) level was found to be increased in an IL-4 dose-dependent manner. IL-4 did not influence the growth or morphological appearance of WI-38 cells. The results demonstrate a novel biological effect of IL-4, modulating GSL in non-hematopoietic cells.

Variations in the ganglioside profile of uveal melanoma correlate with cytologic heterogeneity.

Gangliosides may play an important role in the proliferation and spread of human malignant melanoma. Because the frequency of metastases in uveal and cutaneous melanoma differs, it is possible that they may express different gangliosides. We analyzed the ganglioside profiles of primary uveal melanoma in 14 cases and of cutaneous melanoma metastasis in 19 cases. In cutaneous melanoma, GM3 ranged from 4.2% to 74.6% and GD3 from 22.1% to 91.8% of total lipid-bound sialic acid. GM2 (found in 13 of 19 cases, ranging from 0.5% to 11.7%), GD2 (11/19, 0.5%-22.0%) and 9-O-acetyl-GD3 (13/19, 0.5%-12.6%) were also frequently observed. By contrast, in 11 cases of uveal melanoma, GM3 was > 90%, GD3 was < 10%, GM2 was < 1.1%; neither GD2 nor 9-O-acetyl-GD3 were detected. The ganglioside profiles of these uveal melanomas were virtually identical to those of normal melanocytes obtained from foreskins. Histological examination of these 11 biopsies showed a monomorphous cell composition, but neither infiltration of lymphocytes or melanophages nor cell necrosis was observed. In 3 other cases, GD3 was increased to 19.5%-46.0%. Histological examination of these 3 biopsy specimens showed at least 2 populations of tumor cells that were separable based on morphological grounds, and mononuclear inflammatory cells interspersed among the tumor cells. An increase in GD3 appears to be related to tumor polyclonality and infiltration of the tumor by lymphocytes and macrophages. These results suggest that ganglioside expression of uveal melanoma is associated with host immune responses to the tumor. Furthermore, the low metastatic capacity of uveal melanoma, in contrast to the high metastatic rate of cutaneous melanoma, may be a result of its differentiated ganglioside expression, which is strikingly similar to that of normal melanocytes.

Developmental profiles of gangliosides in trisomy 19 mice

The ganglioside composition of the cerebrum, cerebellum, brainstem, liver, heart, and spleen was analyzed quantitatively in trisomy 19 (Ts19) mice aged 4 to 12 days postpartum. The developmental profiles of cerebral gangliosides were similar in Ts19 mice and control littermates: Total ganglioside-sialic acid as well as the proportions of the individual gangliosides GD1a and GM1 increased with age, while the percentages of GQ1b and GT1b decreased during development. Both the accretion of the total ganglioside content and the development of the individual ganglioside fractions were delayed by 2–3 days in the Ts19 telencephalon. Likewise, the shift from the b- to the a-pathway of ganglioside synthesis was retarded. Ganglioside development was equally delayed in the cerebellum and the brainstem of Ts19 mice. Since in Ts19 mice, morphogenesis of several brain regions is similarly delayed by 2 days, these results confirm the usefulness of gangliosides as biochemical markers for brain maturation. In contrast to brain gangliosides, the ganglioside composition of the Ts19 livers was clearly distinguished from that of control livers. Total ganglioside-bound sialic acid was increased by 35–50% in Ts19 livers. This elevation in ganglioside content not explicable by a simple delay in development was mainly due to an increase in GD3 and fraction 2, which is likely to contain GD1a and GD1b. In contrast, GM2 which increased considerably with age in control mice persisted on a low level in Ts19 livers. Comparable alterations of the ganglioside pattern were neither observed in the spleen nor in the heart of Ts19 mice. The data presented give additional evidence that ganglioside synthesis in the liver is under a different regulation mechanism than that in the brain, heart, and spleen.

Electron spin resonance spectra of Gd3+ ions in K2SO4-ZnSO4 glasses

Electron spin resonance (ESR) spectra of Gd3+ ions doped in K2SO4-ZnSO4 glasses have been studied on an X-band ESR spectrometer at different temperatures (−120 to 150‡ C). The ESR spectrum at room temperature exhibits three prominent features with effectiveg-values of ∼5.6, 2.83 and 2.02. The spectra are similar to the “U” spectra familiar in many oxide and fluoride glasses, indicating very low and disordered site symmetries with a broad distribution of crystal fields. Remarkable changes have been observed in the spectrum with changes in the temperature, concentration and glass composition. The broadening of theg ∼2.02 line with increasing Gd3+ ion content indicates that the dipole-dipole interaction between the resonant centres increases with increase in Gd3+ ion content. A weak band at 36350cm−1 is observed in the optical absorption spectrum of 0.5mol% Gd3+ in K2SO4-ZnSO4 glass which has been assigned to the transition8S7/2→6P7/2.

Ganglioside composition of astrocytes.

Short-term and long-term (greater than 7 months) cultured astrocytes from 14-day-old rat brain were analyzed for ganglioside content. Analysis of the extracted gangliosides by HPTLC revealed that ganglioside GM1 was absent in 35 days and 235 days cultured astrocytes, and that the predominant ganglioside was GM3, showing a double band in both cases. A small amount of the disialogangliosides (GD3, GD1a) was also detected. More than 70% of radioactivities into ganglioside fractions by cultured astrocytes, in the presence of N-[3H]-acetylmannosamine, appeared in ganglioside GM3. The upper band component of GM3 increased 60% in long-term astrocyte cultures compared to 35-day-old cultures. Also, an increased GD3 content in long-term astrocyte cultures was detected. These results suggest that the increase of GD3 and upper band GM3 in long-term cultured astrocytes might be related to the appearance of small processes showing strong reactivity against GFAP and vimentin during astrocyte-subculture.

Hydrogenation of ethylene on gadolinium X, Y and L-type zeolites

It is shown that Gd-zeolites have a catalytic activity towards ethylene hydrogenation at 1 atm. This activity decreases with an increase in the SiO2/Al2O3 ratio from 2.2 to 6.1 and 4.1, i.e. upon going from an X type zeolite to Y and L. For these types of zeolite the activity grows with an increase in Gd3+ content from 50 to 80%. Oxygen addition to the reaction mixture stabilizes the catalytic activity of zeolites.