Percoll Density Gradient Method Research Articles

Detection and Quantification of X and Y sperms in Enriched Sahiwal Semen diluted in PBS using Raman Spectroscopy

The present study was undertaken to enrich X-sperms in Sahiwal bull semen by percoll density gradient method and to detect X and Y sperms in enriched semen by Raman spectroscopy. The experiment was performed at Semen Production Centre, CVASc, GBPUAT, Pantnagar, Uttarakhand. Ejaculates were collected by AV method from Sahiwal bull. X-sperm enrichment was done by the Percoll density gradient method. Three types of gradients were prepared i.e. 7 layers (70-10%), 7 layers (80-20%) and 3 layers (30%, 50% and 70%). Semen (1ml or 3ml) was placed over the gradient in a conical centrifuge tube. Centrifugation was done at 750 g (22-24°C) for 15 min. The pellets thus obtained were diluted in PBS medium. Raman spectroscopy was performed in different groups viz. fresh semen (Control), 3 layers (70%, 50% and 30% GI), 7 layers (70-10% GII), and 7 layers (80-20% GIII). Raman peaks (DNA specific) were not much clear for PBS diluted semen samples though intensities were highest for 7 layers (70-10%) among all groups. Thus semen enriched by the percoll-density gradient method (7 layers i.e. 70-10%) can be used to increase female calf birth after A.I.

Purification of functional mouse skeletal muscle mitochondria using percoll density gradient centrifugation

ObjectiveOur goal was to isolate purified mitochondria from mouse skeletal muscle using a Percoll density gradient and to assess bioenergetic function and purity via Seahorse Extracellular Flux (XF) Analyses and mass spectrometry.ResultsMitochondria isolated from murine quadriceps femoris skeletal muscle using a Percoll density gradient method allowed for minimally contaminated preparations with time from tissue harvest to mitochondrial isolation and quantification in about 3–4 h. Percoll purification from 100 to 200 mg fresh tissue yielded ~ 200–400 ug protein. Mitochondrial bioenergetics evaluated using the Seahorse XFe96 analyzer, a high-throughput respirometry platform, showed optimum mitochondrial input at 500 ng with respiratory control ratio ranging from 3.9 to 7.1 using various substrates demonstrating a high degree of functionality. Furthermore, proteomic analysis of Percoll-enriched mitochondria isolated from skeletal muscle using this method showed significant enrichment of mitochondrial proteins indicating high sample purity. This study established a methodology that ensures sufficient high quality mitochondria for downstream analyses such as mitochondrial bioenergetics and proteomics.

Effect of percoll density gradient centrifugation on semen quality of X- sperm enriched crossbred bull semen

The present study was conducted to observe the effect of percoll density gradient centrifugation on quality of semen. Ejaculates were collected by AV method from Sahiwal bulls. X-sperm enrichment was done by percoll density gradient method i.e. 7 layers (70-10%). Centrifugation was done at 750 g (22-24°C) for 15 min. The pellets obtained were diluted in EYC medium. Semen quality was evaluated in fresh semen (Control), in pellet of normal centrifugation (Group I), supernatant of centrifugation in percoll density gradient (Group II) and pellet of centrifugation in percoll density gradient (Group III). To assess the quality of enriched semen pH, mass motility, progressive motility, live spermatozoa %, abnormal spermatozoa %, HOST % and intact acrosome % were evaluated. Number of progressively motile sperms in pellet of X- enriched semen were non-significantly increased and significantly (P<0.05) decreased in supernatant. The abnormal spermatozoa (%) were decreased in G III as compared to G II Live spermatozoa (%) were increased in enriched semen (pellet). Number of Intact sperms decreased significantly (P<0.05) in supernatant of percoll density gradient centrifuged Sahiwal semen. HOST responsive sperms number was not affected after percoll density gradient centrifugation. Thus, the semen quality of X sperm enriched semen by percoll density gradient method (7 layer 70%) was not affected hence it can be used to increase female calves’ birth after A.I.

Density measurements of aerobic granular sludge

ABSTRACT Granular sludge processes are frequently used in domestic and industrial wastewater treatment. The granule buoyant density and biomass density are important parameters for the design and operation of granular sludge reactors. Different methods to measure the granule density include the pycnometer method, the Percoll density gradient method, the dextran blue method, and the settling velocity method. In this study, a comparison was made between these four methods to measure granule density for granules from a full-scale granular sludge plant treating domestic sewage. The effect of salinity on granule density was assessed as well. Three out of the four evaluated methods yielded comparable results, with granule buoyant densities between 1025.7 and 1028.1 kg/m3 and granule biomass densities between 71.1 and 71.5 g/L (based on volatile suspended solids (VSS)). The settling velocity method clearly underestimated the granule density, due to the complex relation between granule properties and settling velocity. The pycnometer method was the most precise method, but it was also quite susceptible to bias. The granule buoyant density increased proportionally with salinity, to 1049.2 kg/m3 at 36 g/L salinity. However, the granule biomass density, based on VSS, remained constant. This showed that the granule volume was not affected by salinity and that the buoyant density increase was the result of diffusion of salts into the granule pores. Overall, the granule density can be measured reliably with most methods, as long as the effect of salinity is considered. The results are discussed in light of operational aspects for full-scale granular sludge plants.

X-sperm Enrichment of Bovine Semen by Percoll Density Gradient Method and Its Effect on Semen Quality, Sex Ratio and Conception Rate

In cattle, sex selection has a significant economic impact when it improves herd capacity of milk or meat production and is commonly used for the production of calves of the desired gender. New separation techniques which present both better accuracy and low costs are necessary. Density gradient centrifugation might be an approach to sexing spermatozoa because of the additional DNA content and volume of X-bearing sperm head. The present study was designed to apply the modified percoll discontinuous density gradient for X-sperm enrichment in cross bred bovine semen. We attempted to amplify the level of X-sperm enrichment by using double centrifugation in percoll gradient. In addition, effect of percoll density gradient on fertility of semen was also evaluated at three stages; before centrifugation (stage I), after 1st centrifugation (stage II) and after 2nd centrifugation (stage III) respectively and ultrasonography was carried out to confirm the sex of fetus at 60-90 days post AI. Semen was collected from two cross bred bovine bulls and 34 cows were inseminated with liquid X-sperm enriched semen after double centrifugation in percoll gradient. 22 cows were inseminated with non-sexed fresh liquid semen (control). Results showed that the volume, progressive motility, live sperms, concentration and HOST reactive sperms significantly (P is less than 0.05) decreased at stage II and stage III compared to stage I. However, no significant (P is greater than 0.05) change was observed in pH and mass motility of semen at all three stages. There was non-significant effect on per cent spermatozoa with intact acrosomal membrane and fully damaged acrosomal membrane at all three stages however, partially damaged acrosomal membrane sperms were significantly (P is less than 0.05) decreased at Stage II and Stage III compared to Stage I. The conception rate significantly (P is less than 0.05) decreased with X-enriched semen (41.17%) compared to non-sexed liquid semen (59.09%). The female sex ratio of calves significantly (P is less than 0.05) increased to 66.66% with X- sperm enriched semen compared to the male percentage of 33.33% with sexed semen and female percentage of 46.15% with non-sexed semen.

Effects of selection by the Percoll density gradient method on motility, mitochondrial membrane potential and fertility in a subpopulation of Atlantic salmon (Salmo salar) testicular spermatozoa

The aim of this study was to evaluate effects of selection using the Percoll density gradient method on motility, mitochondrial membrane potential (ΔΨMit) and fertility in a subpopulation of testicular spermatozoa obtained from Atlantic salmon (Salmo salar). Samples were divided into three groups: Control (C), T1 (45/90 % Percoll®) and T2 (45/60 % Percoll®). Sperm motility was evaluated using CASA (Computer-Assisted Sperm Analysis), ΔΨMit using flow cytometry, and fertility evaluating whether cleavage of fertilised eggs had occurred after 16 h of incubation at 10 °C. Results indicate that motility was greater in T1 (92 ± 2.91 %) and T2 (89 ± 2.88 %) than in the Control (83.2 ± 2.04 %). The percentage of ΔΨMit was 88.3 ± 0.58 % and 85 ± 2% for T1 and T2, respectively, compared to 35 ± 6.24 % for the control. The fertility rates were 76 ± 9.1 % and 70 ± 8.1 % for T1 and T2, respectively, compared with 66 ± 12 % for the control. The kinetic characteristics for T1 were curvilinear velocity (VCL): 92.44 ± 21.12 μm/s, average path velocity (VAP): 85.87 ± 21.83 μm/s; and for T2 VCL was 78.69 ± 17.63 μm/s and VAP was 73.62 ± 17.08 μm/s. The results indicate sperm motility and ΔΨMit were greater in T1 and T2 compared with the control (P < 0.05). Similarly, there was an increase in the fertilisation rate compared to the control. The results from this study are the first where sperm quality variables were evaluated for Salmo salar testicular sperm using the Percoll® density gradient method.

Cryopreservation effects on a viable sperm sterlet (Acipenser ruthenus) subpopulation obtained by a Percoll density gradient method.

In many fish species, sperm cryopreservation has deleterious effects and leads to a significant decrease in spermatozoa viability. However, the effect of cryopreservation on sperm cells that survive this process and are still viable is not fully understood. The objective of this study was to compare the viability and proteomes of fresh and cryopreserved sterlet (Acipenser ruthenus) sperm samples before and after live-dead cell separation using Percoll density gradient centrifugation. Both fresh and cryopreserved sperm samples were divided into two groups (with or without application of Percoll separation). At each step of the experiment, sperm quality was evaluated by video microscopy combined with integrated computer-assisted sperm analysis software and flow cytometry for live-dead sperm viability analysis. Sperm motility and the percentage of live cells were reduced in the cryopreserved group compared to the fresh group from 89% to 33% for percentage of motility and from 96% to 70% for live cells. Straight line velocity and linearity of track were significantly lower in cryopreserved samples than in those separated by Percoll before and after cryopreservation. However, the percentages of motile and live spermatozoa were higher than 90% in samples subjected to Percoll separation. Proteomic analysis of spermatozoa by two-dimensional differences in-gel electrophoresis coupled with matrix-assisted laser-desorption/ionization time-of-flight/time-of-flight mass spectrometry revealed that 20 protein spot abundances underwent significant changes in cryopreserved samples compared to fresh ones. However, only one protein spot was significantly altered when samples before and after cryopreservation followed by Percoll separation were compared. Thus, the results of this study show that cryopreservation leads to minimal proteomic changes in the spermatozoa population, retaining high motility and viability parameters. The results also suggest that global differences in protein profiles between unselected fresh and cryopreserved samples are mainly due to protein loss or changes in the lethal and sublethal damaged cell subpopulations.

Cellular and plasma nitrite levels in myeloid leukemia: a pathogenetic decrease.

Nitric oxide (NO) has a contributory role in hemopoietic cell growth and differentiation. The effects of NO on leukemic cell growth have been predominantly studied in in vitro settings. This study was done to assess the alterations in nitrite level in myeloid leukemias. Thirty-six newly diagnosed cases of myeloid leukemia (16 AML and 20 CML) were enrolled in the study. Neutrophil precursors from the marrow aspirate and peripheral blood were separated into cell bands using the Percoll density gradient method of Borregard and Cowland. The blood plasma and marrow fluid was also collected. Nitrite (stable non-volatile end product of NO) was estimated in the cell bands, blood plasma and marrow fluid using Griess reagent. The mean nitrite level in all cell bands from peripheral blood, bone marrow, blood plasma, and marrow fluid of cases was significantly lower as compared to corresponding value in the controls. No significant difference between AML and CML was seen. On follow-up, analysis of 13 CML patients higher nitrite levels were seen (p>0.05). The significant decrease in nitrite levels in myeloid leukemia suggests a decrease in nitric oxide synthase (NOS) activity. Further work may unfold molecular targets for therapeutic role of NO modulators.

In vitro culture and characterization of spermatogonial stem cells on Sertoli cell feeder layer in goat (Capra hircus).

To develop an efficient protocol for isolation, purification and long-term culture of spermatogonial stem cell (SSC) in goat. The isolation of SSC was performed by testicular disaggregation by enzymatic digestion using collagenase IV, trypsin and DNase I. Further SSCs were enriched using Percoll density gradient centrifugation. The purity of SSCs was assessed by immunocytochemistry (ICC) using α6 integrin. The SSCs were co-cultured on Sertoli cell feeder layer. The SSC colonies were characterized by studying the expression of SSC specific markers (viz., α6 integrin and PLZF) using ICC. The abundance of mRNAs encoding the markers of SSC (viz., β1 integrin and Oct-4) and Sertoli cells (viz., vimentin) was also assayed using quantitative real-time PCR (qPCR). The viability of isolated testicular cells was > 90% and the Percoll density gradient method resulted in 3.65 folds enrichment with a purity of 82.5%. Co-culturing of SSCs with Sertoli cell feeder layer allowed the maintenance of stable SSC colonies even after one and half months of culture. The results of ICC analysis showed the expression of α6 integrin and PLZF in almost all the SSC colonies. qPCR analysis revealed a differential expression of mRNAs encoding β1 integrin, Oct-4 and vimentin markers. Results of this study demonstrate a simple enzymatic digestion and Percoll density gradient method for isolation and enrichment of SSCs, and suitability of Sertoli cell feeder layer for long term in vitro culture of SSC in goats. Results also suggest the possible application of non-caprine antibodies against SSC specific markers for the identification and subsequent assessment of SSCs in goats.

Detection of discordant HER2 status by FISH in circulating tumor cells and disseminated tumor cells in early-stage breast cancer using a microfluidic-based cell enrichment and extraction platform (OncoCEE).

TPS10631 Background: Evaluation of HER2 in circulating (CTCs) and disseminated (DTC) tumor cells may aid therapy in breast cancer. We report here the discordance in HER2 status in CTCs and DTCs in early stage breast cancer by fluorescence in situ hybridization (FISH) using a microfluidic cell platform (OncoCEE). Methods: Blood (10ml) and BM (1-2ml) from patients with Stage T1 and T2 breast cancer was collected in OncoCEE-Sure collection tubes. Mononuclear cells were recovered using a Percoll density gradient method, incubated with a mixture of 10 primary capture antibodies (Abs), and introduced into streptavidin coated OncoCEE microchannels for tumor cell capture. For blood samples, captured cells were stained with anti cytokeratin (CK) and CD45 Abs for CTC enumeration followed by FISH using probes specific to centromere 17 and HER2. For BM samples, captured cells were subjected to HER2 FISH analysis. The ratio of HER2:CEP17&gt;2.0 in any CK+/ CD45- and CK-/CD45- cell was regarded as positive for HER2. Results: Blood and BM from 68 patients (68 Blood, 54 BM; 54 matched blood and BM) with stage T1N0 (41), T1N1 (6), T2N0 (11), T2N1(2), T2N2 (1), T2N3 (2) with HER2+ (n=7) and HER2- (n=61) breast cancers were studied. The 7 patients with HER2 + primary tumor had HER2+ DTCs in 3/7 (43 %) and HER2 + CTCs in 1/6 (17 %) patients. HER2 + DTCs and HER2 + CTCs occurred in 10/47 (21%) and in 4/57 (7%) patients with HER2- primary breast tumors. The discordance of HER2 status was observed in 14% in CTCs and in 22% in DTCs. Conclusion: 1. The cell enrichment and extraction microfluidic platform (OncoCEE) provides a sensitive approach for evaluation of HER2 in CTCs and DTCs. 2. CTCs and DTCs acquired HER2 gene amplification in 21% and 7% of patients with HER2 negative early stage primary breast cancer. 3. CTCs and DTCs lost HER2 gene amplified status in 57% and 83% of patients with HER2 positive early stage primary breast cancer. 4. The clinical significance of alterations in HER2 status among CTCs and DTCs in early stage breast cancer needs further investigation.

P4-06-04: Detection of HER2 Gene Amplification in Circulating Tumor Cells and Disseminated Tumor Cells by Fluorescence In Situ Hybridization Using OncoCEE™.

Abstract BACKGROUND: The status of HER2 gene amplification in circulating tumor cells (CTCs) and disseminated tumor cells (DTCs) might provide useful information for monitoring response to trastuzumab therapy, and may provide a basis for consideration of trastuzumab in patients with HER2 negative primary tumors who have HER2 positive CTCs and/or DTCs. The majority of techniques utilized for detection of minimal residual disease are limited in their ability to allow detailed phenotypic and genotypic evaluation of the cells. We report the utility of a microfluidic platform (OncoCEE™,Biocept, San Diego) for detecting HER2 gene amplification in CTCs and DTCs in patients with non-metastatic breast cancer. METHODS: Peripheral blood (10ml) and bone marrow (BM) (1-2ml) were collected from patients with clinical stage I-III breast cancer in acid citrate dextrose solution (BD, Franklin Lakes, NJ) and anti-clumping reagent (OncoCEE-Sure™). Mononuclear cells were recovered using a Percoll density gradient method, incubated with a mixture of 10 primary capture antibodies (Abs), introduced into CEE™ microchannels, stained with fluorescent anti cytokeratin (CK) and CD45 abs and finally processed for fluorescence in situ hybridization (FISH) using probes specific to centromere 17 (spectrum green) and HER2 (spectrum arrange). The ratio of HER2:CEP17 &amp;gt;2.2 in any CK+/CD45- and CK-/CD45- cell was regarded as positive for HER2 gene amplification. RESULTS: Peripheral blood and/or BM from 78 patients (65 BM; 70 blood; 57 matched blood and BM) with T1NO (39), T1N1 (8), T2N0 (12), T2N1 (2), T2N2 (1), T2N3 (3), T3N0 (2), T3N1 (2), T3N2 (1), T4N0(5), T4N1 (3), with HER2+ (n=12) and HER2− (n=58) primary invasive breast tumors were studied. The 12 patients with HER2+ primary tumors had HER2+ DTCs in 3/12 (25%) and HER2+ CTCs in 1/9 (11%) cases respectively. HER2+ DTCs and HER2+ CTCs occurred in 12/55 (24%) and in 4/63 (6%) of the patients with HER2− primary breast tumors. HER2+ CTCs and DTCs occurred simultaneously in only 2 patients and in either blood (3) or BM (13) in the remaining patients. CONCLUSION: 1. The cell enrichment and extraction microfluidic technology (OncoCEE™) provides a sensitive platform for evaluation of HER2 gene amplification of CTCs and DTCs. 2. HER2+ primary tumors were associated with either HER2+ CTCs or DTCs in 25% of the patients. 3. HER2+ CTCs or DTCs occurred in 28% of patients with HER2−primary tumor. 4. Discordant HER2 status was contributed mainly by HER2+ DTCs occurring in HER2 - primary tumors. 5. The clinical significance of evaluating the status of HER2 gene amplification in CTCs and DTCs in the management of patients with breast cancer needs to be evaluated prospectively in larger clinical trials. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-06-04.

Stimulation of tube formation mediated through the prostaglandin EP2 receptor in rat luteal endothelial cells

To explore the role of prostaglandin E(2) (PGE(2)) in angiogenesis in the developing corpus luteum, luteal microvascular endothelial-like cells (luteal ECs) were prepared from highly luteinizing ovaries of rats using the percoll density gradient method. The cells abundantly expressed the mRNAs of the endothelial markers CD31 (PECAM-1) and responded to the vascular endothelial growth factor (VEGF) to form in vitro tube structures on Matrigel. Cyclooxygenase (COX) inhibitors significantly suppressed tube formation in luteal ECs, whereas PGE(2) counteracted the COX inhibitor-induced blockage. PGE(2)-induced tube formation was blocked by a cyclic AMP-dependent protein kinase A (PKA) inhibitor, H89. The antagonist against the PGE receptor type 2 (EP2 receptor), AH6809, completely inhibited PGE(2)-induced tube formation and partly suppressed the VEGF-induced tube formation but did not attenuate PGE(2)-induced phosphorylation of both AKT kinase and extracellular signal-regulated kinase 1/2. VEGF significantly enhanced the expression of COX-2 mRNAs detected by real-time RT-PCR and PGE(2) secretion into the media measured by ELISA in luteal ECs. In turn, PGE(2) stimulated VEGF expression. In vitro co-culture of luteal ECs with steroidogenic luteal cells (SLCs) promoted tube formation. Pre-treatment of SLCs with VEGF further enhanced tube formation of ECs, and this effect was blocked by the COX-2 inhibitor. This stimulatory effect was inhibited by treatment with AH6809. These data indicate that PGE(2) exerts a direct stimulatory effect on tube formation mainly via the EP2 receptor/PKA signaling in luteal ECs. Our results suggest the possibility that the endogenous PGE(2) that is produced from luteinizing follicular cells as well as ECs may stimulate luteal angiogenesis.

Mitochondrial Proteomic Analysis of Cytoplasmic Male Sterility Line and Its Maintainer in Wheat ( Triticum aestivum L.)

To investigate the CMS mechanism of wheat on proteomic level and find the crucial proteins which related to fertility, mitochondria was isolated from young spike of wheat by differential centrifugation and Percoll density-gradient methods. Determined by marker enzyme assays and chlorophyll content, the mainly contaminants in the spike mitochondrial fraction were caused by peroxisomes, plastids and chloroplasts after the first discontinuous Percoll density gradient centrifugation. In order to improve the purity of spike mitochondria, a second 28% Percoll self-forming density gradient centrifugation was further carried out, the result showed that the contaminants were decreased to negligible amount, meanwhile the integrity of mitochondria (88%) was improved to 90%. The spike mitochondria proteins extracted from uninucleate stage of (S)-1376A and (A)-1376B were separated by two-dimensional electrophoresis (2-DE), and the silver stained gels were analyzed by PDQuest 2-DE software, about 326 protein spots could be visualized on the 2-DE maps, and also revealed a similar pattern between the male sterile line and its maintainer line, except 11 spots were differentially expressed. A total of five differentially expressed proteins were analyzed by matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS), three of them were identified as manganese superoxide dismutase and T5E216 following NCBInr database by the Mascot software. These results may contribute to further understanding of the mechanisms of CMS in wheat.

The hyperexpressions of putative stem cells in the eutopic endometrium of patients with advanced endometriosis

Objective: Recently it has been proposed that stem cells may be associated with the pathogenesis of endometriosis. The purposes of this study are to investigate whether the eutopic endometrial cells of women with or without endometriosis show the characteristics of stem cells in vitro and have a difference of the expressions of the undifferentiated stem cell markers as OCT-4 and CXCR4. Methods: A total of 6 women with advanced endometriosis and a total of 10 women without endometriosis, adenomyosis or leiomyoma were included in this study. The eutopic endometrial cells, which were obtained from the menstrual blood at menstrual cycle day 2 to 4, were cultured in vitro for approximately 2 weeks, subsequently the putative very small stem cells were separated by Percoll density gradient method and were cultured. The expressions of OCT-4 and CXCR4 were analyzed by real time RT-PCR. Results: The eutopic endometrial cells of the group of endometriosis compared with the control group showed the different morphological characteristics in vitro; more commonly heterogeneous supportive cells, very small round cells less than 3 μm and 515 μm sized hyperchromatic round cells. After the separation of very small round cells by Percoll density gradient method, these cells showed the several characteristics of stem cells; self-renewal, asymmetric cell division, colony formation and embryoid body-like formation. Also These cells showed the similar characteristics of very small embryonic-like stem cells; the mobile cells smaller than erythrocyte, the cell migration or adhesion to supportive cells, the sphere formation by cell aggregation and the formation of new differentiated cell by cell fusion. The expressions of OCT-4 and CXCR4 in the group of endometriosis are respectively 5.66 times and 17.69 times as high as the control group (P

Leishmania major ascorbate peroxidase overexpression protects cells against reactive oxygen species-mediated cardiolipin oxidation

Heme peroxidases are a class of multifunctional redox-active proteins found in all organisms. We recently cloned, expressed, and characterized an ascorbate peroxidase from Leishmania major (LmAPX) that was capable of detoxifying hydrogen peroxide. Localization studies using green fluorescent protein fusions revealed that LmAPX was localized within the mitochondria by its N-terminal signal sequence. Subcellular fractionation analysis of the cell homogenate by the Percoll density-gradient method and subsequent Western blot analysis with anti-LmAPX antibody further confirmed the mitochondrial localization of mature LmAPX. Submitochondrial fractionation analysis showed that the mature enzyme (∼3.6 kDa shorter than the theoretical value of the whole gene) was present in the intermembrane space side of the inner membrane. Moreover, expression of the LmAPX gene was increased by treatment with exogenous H 2O 2, indicating that LmAPX was induced by oxidative stress. To investigate the biological role of LmAPX we generated Leishmania cells overexpressing LmAPX in the mitochondria. Flow-cytometric analysis, thin-layer chromatography, and IC 50 measurements suggested that overexpression of LmAPX caused depletion of the mitochondrial ROS burden and conferred a protection against mitochondrial cardiolipin oxidation and increased tolerance to H 2O 2. These results suggest that the single-copy LmAPX gene plays a protective role against oxidative damage.

Mitochondria Are a Major Source of Paraquat-induced Reactive Oxygen Species Production in the Brain

Paraquat (PQ(2+)) is a prototypic toxin known to exert injurious effects through oxidative stress and bears a structural similarity to the Parkinson disease toxicant, 1-methyl-4-pheynlpyridinium. The cellular sources of PQ(2+)-induced reactive oxygen species (ROS) production, specifically in neuronal tissue, remain to be identified. The goal of this study was to determine the involvement of brain mitochondria in PQ(2+)-induced ROS production. Highly purified rat brain mitochondria were obtained using a Percoll density gradient method. PQ(2+)-induced hydrogen peroxide (H(2)O(2)) production was measured by fluorometric and polarographic methods. The production of H(2)O(2) was evaluated in the presence of inhibitors and modulators of the mitochondrial respiratory chain. The results presented here suggest that in the rat brain, (a) mitochondria are a principal cellular site of PQ(2+)-induced H(2)O(2) production, (b) PQ(2+)-induced H(2)O(2) production requires the presence of respiratory substrates, (c) complex III of the electron transport chain is centrally involved in H(2)O(2) production by PQ(2+), and (d) the mechanism by which PQ(2+) generates H(2)O(2) depends on the mitochondrial inner transmembrane potential. These observations were further confirmed by measuring PQ(2+)-induced H(2)O(2) production in primary neuronal cells derived from the midbrain. These findings shed light on the mechanism through which mitochondria may contribute to ROS production by other environmental and endogenous redox cycling agents implicated in Parkinson's disease.

Effect of NMDA receptor antagonist on proliferation of neurospheres from embryonic brain

The N-methyl-D-aspartate (NMDA) receptor, a subtype of ionotropic glutamate receptors, plays an important role in the regulation of neuronal development, learning and memory, and neurodegenerative diseases. NMDA receptor blockade enhances neurogenesis in the hippocampal dentate gyrus in vivo. The effect of NMDA receptor antagonist on proliferation of neural progenitor cells, however, remains to be determined. We investigated changes in the diameter and number of neurospheres derived from the embryonic rat brain after NMDA receptor blockade. Cortical progenitor cells were isolated from gestational day 18 fetal rats according to the Percoll density gradient method. Cultured spheres expressed neural progenitor markers, musashi-1 and nestin. Immunohistochemical analysis demonstrated that cells in Dulbecco's modified Eagle medium/F12 containing 1% fetal bovine serum on day 8 differentiated to MAP-2-positive neurons and GFAP-positive astrocytes. The expression of NR1 and NR2B subunits of the NMDA receptor in neurospheres was detected. Neither brief nor sustained exposure to NMDA altered the diameter and number of neurospheres. Brief exposure to 30 μM MK-801, an NMDA receptor antagonist, decreased the diameter of neurospheres. Sustained exposure to 30 μM MK-801 decreased the diameter and number of neurospheres. Our results provide evidence that MK-801 directly decreased proliferation of neural progenitor cells.

Comparison of Two Methods for Preparing Mitochondria from Tomato Leaves to Study the Ascorbate-Glutathione Cycle Activity

Mitochondria were purified from tomato leaves by a differential centrifugation method and a Percoll density-gradient method. A comparative study on the ascorbate-glutathione cycle activity revealed that there was no difference in the specific activity of the antioxidative enzymes and ascorbate and glutathione concentrations between mitochondria prepared by these two methods. However, the contents of dehydroascorbic acid and oxidised glutathione in Percoll-separated organelles were 260 and 210 %, respectively, of those found in mitochondria purified by the differential centrifugation method.

Supply of O2 regulates demand for O2 and uptake of malate by N2-fixing bacteroids from soybean nodules.

Bacteroids, prepared anaerobically from soybean root nodules by fractional centrifugation or by sucrose or Percoll density-gradient methods, were retained within a stirred, flow-through reaction chamber and used to determine rates of respiration and N2 fixation at various rates of O2 supply. Liquid reaction solutions containing malate, oxyleghaemoglobin, dissolved N2 and various levels of dissolved O2 were passed through the reaction chamber at measured rates of flow. The relative oxygenation of leghaemoglobin in the chamber was determined automatically by spectrophotometry of the effluent solution, and the concentrations of free, dissolved O2 ([O2(free)]) and the rates of O2 consumption were calculated. N2 fixation was measured by analysis of fractions of effluent. The principal finding was that stepwise increases in the flow rate (increasing the supply of O2 and malate) induced an increase in O2 demand (respiration) resulting in a decrease in [O2(free)] and increased N2 fixation. In some experiments, samples of bacteroids were withdrawn from the flow chamber during steady states and the rates of malate uptake were measured in standard, microaerobic assays. Progressive taking of samples from the flow chamber whilst maintaining constant flow rates (increasing the supply of O2 and malate per bacteroid) also resulted in increased O2 demand and declines in [O2(free)]. With increased bacteroid respiration, transport of malate into bacteroids (linear with time between 1 and 5 min after starting each assay) increased proportionally. This suggests that the rate of malate transport is tightly coupled with bacteroid respiration. Thus, bacteroid respiration, coupled with malate uptake, must be regulated by the rate of O2 supply, rather than by the [O2(free)] prevailing in the stirred chamber as found or assumed in previous work. These features are discussed in relation to N2 fixation by anaerobically isolated bacteroids.

A Comparison of Pure Sperm and Percoll Density Gradients for Sperm Separation in Intracytoplasmic Sperm Injection (ICSI)

Objectives: Although Percoll density gradient method has been used successfully over the years, it has been recently withdrawn in many IVF clinics due to concerns regarding its toxic effects. In this study we evaluated our initial experiences with a new sperm separation method “Pure sperm” and we compared it with Percoll density gradient.