Tissue Culture Incubator Research Articles

Solubilization and purification of recombinant modified C-reactive protein from inclusion bodies using reversible anhydride modification.

The precise function of C-reactive protein (CRP) as a regulator of inflammation in health and disease continues to evolve. The true understanding of its role in host defense responses has been hampered by numerous reports of comparable systems with contradictory interpretations of CRP as a stimulator, suppressor, or benign contributor to such processes. These discrepancies may be explained in part by the existence of a naturally occurring CRP isoform, termed modified CRP (i.e., mCRP), that is expressed when CRP subunits are dissociated into monomeric structures. The free mCRP subunit undergoes a non-proteolytic conformational change that has unique solubility, antigenicity, and bioactivity compared to the subunits that remain associated in the native, pentameric CRP molecule (i.e., pCRP). As specific reagents have been developed to identify and quantify mCRP, it has become apparent that this isoform can be formed spontaneously in calcium-free solutions. Furthermore, mCRP can be expressed on perturbed cell membranes with as little as 24–48 h incubation in tissue culture. Because mCRP has the same size as pCRP subunits as evaluated by SDS-PAGE, its presence in a pCRP reagent would not be apparent using this technique to evaluate purity. Finally, because many antibody reagents purported to be specific for “CRP” contains some, or substantial specificity to mCRP, antigen-detection techniques using such reagents may fail to distinguish the specific CRP isoform detected. All these caveats concerning CRP structures and measurements suggest that the aforementioned contradictory studies may reflect to some extent on distinctive bioactivities of mCRP rather than on pCRP. To provide a reliable, abundant supply of mCRP for separate and comparable studies, a recombinant protein was engineered and expressed in E. coli (i.e., recombinant mCRP or rmCRP). Synthesized protein was produced as inclusion bodies which proved difficult to solubilize for purification and characterization. Herein, we describe a method using anhydride reagents to effectively solubilize rmCRP and allow for chromatographic purification in high yield and free of contaminating endotoxin. Furthermore, the purified rmCRP reagent represents an excellent comparable protein to the biologically produced mCRP and as a distinctive reagent from pCRP. Deciphering the true function of CRP in both health and disease requires a knowledge, understanding, and reliable supply of each of its structures so to define the distinctive effects of each on the body’s response to tissue damaging events.

1(st) trimester miscarriage: four decades of study.

Miscarriage is a very common occurrence in humans. This paper sets out to present published data on research that has provided increased understanding of pregnancy failure. Clarification of definitions, exploring the range of failures from preclinical to later pregnancy losses, and the scientific tools employed to find information on the losses have been documented. What is now understood, which tools work best, and the associated limitations are all discussed. Early studies used cytogenetic methods and tissue culture to obtain results. Improvements in laboratory tools such as better tissue culture incubators, inverted microscopes, laminar flow hoods, improvements in culture media, all contributed to obtaining more results for patients. These studies demonstrated the significant contribution of unbalanced chromosomal karyotypes to pregnancy failure. Maternal age as a contributing factor in trisomy was clearly demonstrated. First trimester miscarriage exhibits very high cytogenetic abnormality; in contrast to very low rates in later losses. Combining data across all time periods of pregnancy will affect the significance of chromosomal error in the early pregnancy failures. Cytogenetic methods investigate whole genomes, and are considered to represent the standard against which new methods must be validated. New molecular genetic methods provide the opportunity to examine samples without the necessity of tissue culture. Techniques may be site-specific or whole genome. Fluorescent in situ hybridisation (FISH), comparative genomic hybridisation (CGH), array-based CGH, single nucleotide polymorphism (SNP) detection, quantitative polymerase chain reaction (qPCR), and quantitative fluorescent PCR (QF-PCR), have all been utilised. In comparison studies with classical/conventional cytogenetics, each newer method offers advantages and limitations. At the present time, a combined approach using conventional and molecular methods will elucidate the cause of miscarriage for almost all samples. In a clinical setting this would be optimum.

217 THE EXPRESSION OF β-OXIDATION RELATING GENES UNDER HYPOXIC STRESS IN HUMAN PLACENTAL CHORIOCARCINOMA CELL (BeWo)

Preeclampsia (PE) is thought in many cases to be caused by a shallowly implanted placenta that becomes hypoxic. Hypoxia can result from a failure at any stage in the delivery of oxygen to the cells. In peripheral tissues, oxygen diffuses down a pressure gradient into cells and moves into their mitochondria, where it is used to produce energy in conjunction with the breakdown of glucose, fats, and some amino acids. The aim of the study was to investigate the question of whether hypoxic stress is involved in β-oxidation of human placental BeWo cells. One of the β-oxidation related genes, ACADVL was detected by gene-fishing technology using the preeclamptic placenta of human. We conducted in vitro experiments to confirm a preliminary study by inducing hypoxic stress in the human placental BeWo cell. BeWo cells were cultured at 37°C in a 20% O2, 5% CO2 humidified tissue culture incubator. And then we induced hypoxic stress in BeWo cell cultured under 1% O2, 5% CO2, and balanced with N2. The BeWo cells were divided into three groups: normoxia, hypoxia 24 h, and hypoxia 48 h. The expression of β-oxidation related genes (ACADVL, EHHADH, HADH, ACAA) were observed under hypoxic condition in BeWo cells by using real-time RT-PCR. Relative quantification with HPRT1 was based on the comparison of CT at a constant fluorescent intensity. The amount of transcript is inversely related to the observed CT, and for every 2-fold dilution in the transcript, CT is expected to increase by 1. Relative expression was calculated using the equation R = 2–(CTsample – CTcontrol). Data were analysed with a nonparametric one-way ANOVA, followed by Tukey's test for multiple comparisons. All statistical analyses were performed using GraphPad Prism software (v 4.0, GraphPad Software, La Jolla, CA, USA). P-values <0.05 were considered statistically significant. The expression of a gene known as a biomarker for hypoxia, HIF-1a, was significantly increased in BeWo cells which induced preeclampsia. The elevated level of HIF-1a indicates that our experimental conditions closely mimicked preeclampsia. The β-oxidation related genes, ACADVL, EHHADH, and HADH expressions were significantly increased under hypoxic condition in BeWo compared with normoxic control. These results indicate that changes of β-oxidation related genes observed under hypoxic BeWo cells are similar to ones associated with preeclampsia, and the expression of β-oxidation related genes were up-regulated by hypoxic stress. They might be involved in pathogenesis of preeclampsia during gestation. Taken together, increase of β-oxidation-related genes under hypoxic stress may cause a compensation of energy metabolism deficiency through lipid metabolism.

Long-term time lapse imaging of mouse cochlear explants.

Here we present a method for long-term time-lapse imaging of live embryonic mouse cochlear explants. The developmental program responsible for building the highly ordered, complex structure of the mammalian cochlea proceeds for around ten days. In order to study changes in gene expression over this period and their response to pharmaceutical or genetic manipulation, long-term imaging is necessary. Previously, live imaging has typically been limited by the viability of explanted tissue in a humidified chamber atop a standard microscope. Difficulty in maintaining optimal conditions for culture growth with regard to humidity and temperature has placed limits on the length of imaging experiments. A microscope integrated into a modified tissue culture incubator provides an excellent environment for long term-live imaging. In this method we demonstrate how to establish embryonic mouse cochlear explants and how to use an incubator microscope to conduct time lapse imaging using both bright field and fluorescent microscopy to examine the behavior of a typical embryonic day (E) 13 cochlear explant and Sox2, a marker of the prosensory cells of the cochlea, over 5 days.

Abstract 2379: 96-Well CometChip validation for simultaneous treatment and measurement of DNA damage in a single platform

Abstract The 96-Well CometChip System is a high-throughput platform to simultaneously treat and measure DNA damage induced by different treatments, or among different cell types on a single slide using the comet assay. The CometChip is a consumable consisting of specifically sized micron pores patterned into agarose layered on a treated microscope slide. Ninety-six (96) separate wells are created by inserting the CometChip into a reusable 96-Well CometChip System, a magnetically-sealed cassette suitable for tissue culture incubators. Cells added to each well are captured by gravity into micropores and excess cells aspirated leaving an array of non-overlapping cells. Multiple experimental conditions are performed in parallel by the addition of different chemicals to respective wells. Once treatment is complete the CometChip is removed from the cassette and processed using standard alkaline comet conditions and imaging systems. A distributable CometChip requires precision manufacturing to ensure robust and reproducible performance. CometChip tolerances were investigated and compared to normal comet using cryopreserved comet control cells with known levels of DNA damage. After setting specifications, 96-Well CometChips with 30 micron pores were distributed to evaluate both intra and inter-chip variations between laboratories. To assure experimental consistency between labs, magnetically sealable cassettes, cryopreserved control cells and identical electrophoresis systems were provided to each lab. Data is presented to demonstrate the feasibility of manufacturing the CometChip for reproducible results based on the coefficients of variance (CVs) obtained between different wells and laboratories. In addition, data will be presented demonstrating the absence of cross talk between CometChip wells using the 96-Well CometChip System. (Work was supported by R44ES021116). Citation Format: Sandra R. Woodgate, Clare Whittaker, Jay George, Robert W. Sobol, Sandy Schamus-Haynes, Bevin P. Engelward, Jing Ge. 96-Well CometChip validation for simultaneous treatment and measurement of DNA damage in a single platform. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2379. doi:10.1158/1538-7445.AM2014-2379

Preparation of Tumor Antigen-loaded Mature Dendritic Cells for Immunotherapy

While clinical studies have established that antigen-loaded DC vaccines are safe and promising therapy for tumors, their clinical efficacy remains to be established. The method described below, prepared in accordance with Good Manufacturing Process (GMP) guidelines, is an optimization of the most common ex vivo preparation method for generating large numbers of DCs for clinical studies. Our method utilizes the synthetic TLR 3 agonist Polyinosinic-Polycytidylic Acid-poly-L-lysine Carboxymethylcellulose (Poly-ICLC) to stimulate the DCs. Our previous study established that Poly-ICLC is the most potent individual maturation stimulus for human DCs as assessed by an upregulation of CD83 and CD86, induction of interleukin-12 (IL-12), tumor necrosis factor (TNF), interferon gamma-induced protein 10 (IP-10), interleukmin 1 (IL-1), and type I interferons (IFN), and minimal interleukin 10 (IL-10) production. DCs are differentiated from frozen peripheral blood mononuclear cells (PBMCs) obtained by leukapheresis. PBMCs are isolated by Ficoll gradient centrifugation and frozen in aliquots. On Day 1, PBMCs are thawed and plated onto tissue culture flasks to select for monocytes which adhere to the plastic surface after 1-2 hr incubation at 37 °C in the tissue culture incubator. After incubation, the lymphocytes are washed off and the adherent monocytes are cultured for 5 days in the presence of interleukin-4 (IL-4) and granulocyte macrophage-colony stimulating factor (GM-CSF) to differentiate to immature DCs. On Day 6, immature DCs are pulsed with the keyhole limpet hemocyanin (KLH) protein which serves as a control for the quality of the vaccine and may boost the immunogenicity of the vaccine. The DCs are stimulated to mature, loaded with peptide antigens, and incubated overnight. On Day 7, the cells are washed, and frozen in 1 ml aliquots containing 4-20 x 10(6) cells using a controlled-rate freezer. Lot release testing for the batches of DCs is performed and must meet minimum specifications before they are injected into patients.

AB0224 Oaz regulate B-cell functions through the inhibition of CCL2 expression in mesenchymal stem cells

BackgroundMesenchymal stem cells (MSCs) had been indicated to exert suppressive effects on B-cell proliferation and differentiation through released humoral factor(s) yet to be defined, which is impaired in patients with...

SAT0244 Correlation between circulating TFH cells and disease activity as well as autoantibody production in chinese patients with systemic lupus erythematosus

BackgroundPreviously we have shown that interleukin-21 (IL-21) level was tightly associated with anti-nuclear antibody (ANA) production in cultured peripheral blood mononuclear cells (PBMCs) from patients with systemic lupus erythematosus (SLE)...

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Design of a Biaxial Mechanical Loading Bioreactor for Tissue Engineering

We designed a loading device that is capable of applying uniaxial or biaxial mechanical strain to a tissue engineered biocomposites fabricated for transplantation. While the device primarily functions as a bioreactor that mimics the native mechanical strains, it is also outfitted with a load cell for providing force feedback or mechanical testing of the constructs. The device subjects engineered cartilage constructs to biaxial mechanical loading with great precision of loading dose (amplitude and frequency) and is compact enough to fit inside a standard tissue culture incubator. It loads samples directly in a tissue culture plate, and multiple plate sizes are compatible with the system. The device has been designed using components manufactured for precision-guided laser applications. Bi-axial loading is accomplished by two orthogonal stages. The stages have a 50 mm travel range and are driven independently by stepper motor actuators, controlled by a closed-loop stepper motor driver that features micro-stepping capabilities, enabling step sizes of less than 50 nm. A polysulfone loading platen is coupled to the bi-axial moving platform. Movements of the stages are controlled by Thor-labs Advanced Positioning Technology (APT) software. The stepper motor driver is used with the software to adjust load parameters of frequency and amplitude of both shear and compression independently and simultaneously. Positional feedback is provided by linear optical encoders that have a bidirectional repeatability of 0.1 μm and a resolution of 20 nm, translating to a positional accuracy of less than 3 μm over the full 50 mm of travel. These encoders provide the necessary position feedback to the drive electronics to ensure true nanopositioning capabilities. In order to provide the force feedback to detect contact and evaluate loading responses, a precision miniature load cell is positioned between the loading platen and the moving platform. The load cell has high accuracies of 0.15% to 0.25% full scale.

Encapsulation of chondrocytes in physiologically-stiff agarose

Purpose: The cellular microenvironment contains insoluble matrix, soluble signals and nutrients, and extracellular water, to maintain cell and tissue homeostasis. Articular chondrocytes reside within a pericellular matrix (PCM) defining their immediate surroundings and providing both molecular and mechanical signals. One biomechanical cue, which alters cellular phenotype is stiffness, which is provided by the PCM. Differences in PCM stiffness have been found between normal and osteoarthritic chondrons, with measured values of w25200 kPa. The objective of this study was to test the hypothesis that cultured chondrocytes can be encapsulated in high-concentration agarose gels of physiological stiffness. Our novel results suggest that agarose can provide a 3D microenvironment capable of both maintaining cellular viability and mimicking the PCM stiffness of both normal and OA tissue. Methods: Cylindrical agarose gels were prepared in PBS and maintained at 4 C until mechanical testing (<48 hours) when samples were compressed in increments of 4% nominal compression followed by 2 hours of stress-relaxation through 16% final compression. Nominal stresses were calculated by dividing the load by the measured cross sectional area. Linear regression was used to determine dynamic and equilibrium stiffness values from the stress (peak and equilibrium) and strain data. SW1353 chondrocytic cells were grown in DMEM with 10% calf serum and antibiotics. Cells were trypsinized, counted, pelleted (600 x g, 7 minutes), and resuspended in media at 3 x 10^6 cells / mL (11X). Agarose was dissolved in PBS at 1.1X (4.4% w / v). Cell suspensions and agarose solutions were mixed prior to casting at 25 C for 10 minutes before incubation in tissue culture (37 C, 5% CO2, DMEM with 10% serum and antibiotics). Viability was assessed after 24 hours in tissue culture by incubating cells in 50 mg / mL propidium iodide (PI) and 5 mM Calcein-AM in PBS for 1 hour. Samples were imaged in PBS on a Leica SP5 upright confocal microscope using a 25X submersible objective. Cells were counted using Leica software following thresholding. Statistical analyses were performedwith an a priori significance level of a1⁄40.05. Results: A significant relationship was found between the stiffness and gel concentration (Figure 1, Dynamic: r 1⁄4 0.79. Equilibrium: r 1⁄4 0.92 Both p< 0.001, n1⁄4 5). We achieved agarose equilibrium stiffness values as large as 51.3 kPa (Figure 1). At 4.0% agarose, we found equilibrium moduli of 34.3 +/1.65 kPa, and at 4.5% agarose, we found equilibrium moduli of 35.7 +/0.95 kPa. Imaging revealed high viability (Figure 2), and 95% confidence intervals for the number of PI positive nuclei upon detergent addition were not location-specific indicating that the methods resulted in an even spatial distribution of cells. Furthermore, we found no viability differences between regions. Overall viability was 94.0 1.0% (n1⁄43). Conclusions: These data demonstrate the feasibility of encapsulating chondrocytic cells in agarose of physiological stiffness. Because the stiffness of the pericellular matrix is affected by osteoarthritis these methods provide a foundation for both improving the physiological relevance of in vitro culture systems and applying mechanical loads to chondrocytes. 242 REVERSAL OF THE NEGATIVE EFFECTS OF TGFb1 ON HUMAN ARTICULAR CHONDROCYTES BY PKCd INHIBITION WITH ROTTLERIN L. Lugo y, S. Piera-Velazquez z, G. Herrero-Beaumont y, S.A. Jimenez z. y IIS-Fundacion Jimenez Diaz, Madrid, Spain; z Thomas Jefferson Univ., Philadelphia, PA, USA

Critical role of Th17 cells in development of autoimmune hemolytic anemia

Autoimmune hemolytic anemia (AIHA) is defined as the increased destruction of red blood cells (RBCs) in the presence of anti-RBC autoantibodies with or without complement activation. However, the underlying mechanism for the development of AIHA remains largely unclear. In this study, we carefully evaluated the potential role of Th17 cells in the development of AIHA. We found an elevated frequency of Th17 cells in patients with AIHA, which were closely correlated with their disease activity, including the level of anti-RBC IgG antibodies, hemoglobin, serum C3, and lactate dehydrogenase activity. Furthermore, we observed that interleukin (IL)-17 was also closely correlated with the disease activity in AIHA patients. To further elucidate the potential role of Th17 cells in induction of AIHA, we used the Marshall-Clarke and Playfair model of murine AIHA. Notably, we found that Th17 cells affected development of AIHA by enhancing the adaptive humoral responses. Specifically, we found that adoptive transfer of Th17 cells heightened the initial anti-rat RBC antibody responses and concomitantly increased the onset of AIHA. In addition, invivo neutralization of IL-17 abrogated the development of AIHA, while initiation of anti-rat RBC IgG responses and induction of AIHA in IL-17(-/-) mice were impaired. Our findings suggest that Th17 cells contribute to the development of AIHA, which could facilitate our better understanding of AIHA pathogenesis and provide clues to developing novel forms of immunotherapy against AIHA.

Hypercapnia Induces Cleavage and Nuclear Localization of RelB Protein, Giving Insight into CO2 Sensing and Signaling

Carbon dioxide (CO(2)) is increasingly being appreciated as an intracellular signaling molecule that affects inflammatory and immune responses. Elevated arterial CO(2) (hypercapnia) is encountered in a range of clinical conditions, including chronic obstructive pulmonary disease, and as a consequence of therapeutic ventilation in acute respiratory distress syndrome. In patients suffering from this syndrome, therapeutic hypoventilation strategy designed to reduce mechanical damage to the lungs is accompanied by systemic hypercapnia and associated acidosis, which are associated with improved patient outcome. However, the molecular mechanisms underlying the beneficial effects of hypercapnia and the relative contribution of elevated CO(2) or associated acidosis to this response remain poorly understood. Recently, a role for the non-canonical NF-κB pathway has been postulated to be important in signaling the cellular transcriptional response to CO(2). In this study, we demonstrate that in cells exposed to elevated CO(2), the NF-κB family member RelB was cleaved to a lower molecular weight form and translocated to the nucleus in both mouse embryonic fibroblasts and human pulmonary epithelial cells (A549). Furthermore, elevated nuclear RelB was observed in vivo and correlated with hypercapnia-induced protection against LPS-induced lung injury. Hypercapnia-induced RelB processing was sensitive to proteasomal inhibition by MG-132 but was independent of the activity of glycogen synthase kinase 3β or MALT-1, both of which have been previously shown to mediate RelB processing. Taken together, these data demonstrate that RelB is a CO(2)-sensitive NF-κB family member that may contribute to the beneficial effects of hypercapnia in inflammatory diseases of the lung.

Recurrent Aspergillus contamination in a biomedical research facility: a case study

Fungal contamination of biomedical processes and facilities can result in major revenue loss and product delay. A biomedical research facility (BRF) culturing human cell lines experienced recurring fungal contamination of clean room incubators over a 3-year period. In 2010, as part of the plan to mitigate contamination, 20 fungal specimens were isolated by air and swab samples at various locations within the BRF. Aspergillus niger and Aspergillus fumigatus were isolated from several clean-room incubators. A. niger and A. fumigatus were identified using sequence comparison of the 18S rRNA gene. To determine whether the contaminant strains isolated in 2010 were the same as or different from strains isolated between 2007 and 2009, a novel forensic approach to random amplified polymorphic DNA (RAPD) PCR was used. The phylogenetic relationship among isolates showed two main genotypic clusters, and indicated the continual presence of the same A. fumigatus strain in the clean room since 2007. Biofilms can serve as chronic sources of contamination; visual inspection of plugs within the incubators revealed fungal biofilms. Moreover, confocal microscopy imaging of flow cell-grown biofilms demonstrated that the strains isolated from the incubators formed dense biofilms relative to other environmental isolates from the BRF. Lastly, the efficacies of various disinfectants employed at the BRF were examined for their ability to prevent spore germination. Overall, the investigation found that the use of rubber plugs around thermometers in the tissue culture incubators provided a microenvironment where A. fumigatus could survive regular surface disinfection. A general lesson from this case study is that the presence of microenvironments harboring contaminants can undermine decontamination procedures and serve as a source of recurrent contamination.

Neuromodulation and Mitochondrial Transport: Live Imaging in Hippocampal Neurons over Long Durations

To understand the relationship between mitochondrial transport and neuronal function, it is critical to observe mitochondrial behavior in live cultured neurons for extended durations1-3. This is now possible through the use of vital dyes and fluorescent proteins with which cytoskeletal components, organelles, and other structures in living cells can be labeled and then visualized via dynamic fluorescence microscopy. For example, in embryonic chicken sympathetic neurons, mitochondrial movement was characterized using the vital dye rhodamine 1234. In another study, mitochondria were visualized in rat forebrain neurons by transfection of mitochondrially targeted eYFP5. However, imaging of primary neurons over minutes, hours, or even days presents a number of issues. Foremost among these are: 1) maintenance of culture conditions such as temperature, humidity, and pH during long imaging sessions; 2) a strong, stable fluorescent signal to assure both the quality of acquired images and accurate measurement of signal intensity during image analysis; and 3) limiting exposure times during image acquisition to minimize photobleaching and avoid phototoxicity.Here, we describe a protocol that permits the observation, visualization, and analysis of mitochondrial movement in cultured hippocampal neurons with high temporal resolution and under optimal life support conditions. We have constructed an affordable stage-top incubator that provides good temperature regulation and atmospheric gas flow, and also limits the degree of media evaporation, assuring stable pH and osmolarity. This incubator is connected, via inlet and outlet hoses, to a standard tissue culture incubator, which provides constant humidity levels and an atmosphere of 5-10% CO2/air. This design offers a cost-effective alternative to significantly more expensive microscope incubators that don't necessarily assure the viability of cells over many hours or even days. To visualize mitochondria, we infect cells with a lentivirus encoding a red fluorescent protein that is targeted to the mitochondrion. This assures a strong and persistent signal, which, in conjunction with the use of a stable xenon light source, allows us to limit exposure times during image acquisition and all but precludes photobleaching and phototoxicity. Two injection ports on the top of the stage-top incubator allow the acute administration of neurotransmitters and other reagents intended to modulate mitochondrial movement. In sum, lentivirus-mediated expression of an organelle-targeted red fluorescent protein and the combination of our stage-top incubator, a conventional inverted fluorescence microscope, CCD camera, and xenon light source allow us to acquire time-lapse images of mitochondrial transport in living neurons over longer durations than those possible in studies deploying conventional vital dyes and off-the-shelf life support systems.

Neuromodulation and Mitochondrial Transport: Live Imaging in Hippocampal Neurons over Long Durations

To understand the relationship between mitochondrial transport and neuronal function, it is critical to observe mitochondrial behavior in live cultured neurons for extended durations1-3. This is now possible through the use of vital dyes and fluorescent proteins with which cytoskeletal components, organelles, and other structures in living cells can be labeled and then visualized via dynamic fluorescence microscopy. For example, in embryonic chicken sympathetic neurons, mitochondrial movement was characterized using the vital dye rhodamine 1234. In another study, mitochondria were visualized in rat forebrain neurons by transfection of mitochondrially targeted eYFP5. However, imaging of primary neurons over minutes, hours, or even days presents a number of issues. Foremost among these are: 1) maintenance of culture conditions such as temperature, humidity, and pH during long imaging sessions; 2) a strong, stable fluorescent signal to assure both the quality of acquired images and accurate measurement of signal intensity during image analysis; and 3) limiting exposure times during image acquisition to minimize photobleaching and avoid phototoxicity. Here, we describe a protocol that permits the observation, visualization, and analysis of mitochondrial movement in cultured hippocampal neurons with high temporal resolution and under optimal life support conditions. We have constructed an affordable stage-top incubator that provides good temperature regulation and atmospheric gas flow, and also limits the degree of media evaporation, assuring stable pH and osmolarity. This incubator is connected, via inlet and outlet hoses, to a standard tissue culture incubator, which provides constant humidity levels and an atmosphere of 5-10% CO2/air. This design offers a cost-effective alternative to significantly more expensive microscope incubators that don't necessarily assure the viability of cells over many hours or even days. To visualize mitochondria, we infect cells with a lentivirus encoding a red fluorescent protein that is targeted to the mitochondrion. This assures a strong and persistent signal, which, in conjunction with the use of a stable xenon light source, allows us to limit exposure times during image acquisition and all but precludes photobleaching and phototoxicity. Two injection ports on the top of the stage-top incubator allow the acute administration of neurotransmitters and other reagents intended to modulate mitochondrial movement. In sum, lentivirus-mediated expression of an organelle-targeted red fluorescent protein and the combination of our stage-top incubator, a conventional inverted fluorescence microscope, CCD camera, and xenon light source allow us to acquire time-lapse images of mitochondrial transport in living neurons over longer durations than those possible in studies deploying conventional vital dyes and off-the-shelf life support systems.

Organotypic Slice Culture of GFP-expressing Mouse Embryos for Real-time Imaging of Peripheral Nerve Outgrowth

For many purposes, the cultivation of mouse embryos ex vivo as organotypic slices is desirable. For example, we employ a transgenic mouse line (tauGFP) in which the enhanced version of the green fluorescent protein (EGFP) is exclusively expressed in all neurons of the developing central and peripheral nervous system1, allowing the possibility to both film the innervation of the forelimb and to manipulate this process with pharmacological and genetic techniques2. The most critical parameter in the successful cultivation of such slice cultures is the method by which the slices are prepared. After extensive testing of a variety of methods, we have found that a vibratome is the best possible device to slice the embryos such that they routinely result in a culture that demonstrates viability over a period of several days, and most importantly, develops in an age-specific manner. For mid-gestation embryos, this includes the normal outgrowth of spinal nerves from the spinal cord and the dorsal root ganglia to their targets in the periphery and the proper determination of skeletal and muscle tissue. In this work, we present a method for processing whole embryos of embryonic day (E) E10 to E12 into 300 - 400 micrometer slices for cultivation in a standard tissue culture incubator, which can be studied for up to two days after slice preparation. Critical for the success of this approach is the use of a vibratome to slice each agarose-embedded embryo. This is followed by the cultivation of the slices upon Millicell culture membrane inserts placed upon a small volume of medium, resulting in an interface culture technique. One litter with an average of 7 embryos routinely produces at least 14 slices (2-3 slices of the forelimb region per embryo), which varies slightly due to the age of the embryos as well as to the thickness of the slices. About 80% of the cultured slices show nerve outgrowth, which can be measured througout the culturing period2. Representative results using the tauGFP mouse line are demonstrated.

Organotypic Slice Culture of GFP-expressing Mouse Embryos for Real-time Imaging of Peripheral Nerve Outgrowth

For many purposes, the cultivation of mouse embryos ex vivo as organotypic slices is desirable. For example, we employ a transgenic mouse line (tauGFP) in which the enhanced version of the green fluorescent protein (EGFP) is exclusively expressed in all neurons of the developing central and peripheral nervous system(1), allowing the possibility to both film the innervation of the forelimb and to manipulate this process with pharmacological and genetic techniques(2). The most critical parameter in the successful cultivation of such slice cultures is the method by which the slices are prepared. After extensive testing of a variety of methods, we have found that a vibratome is the best possible device to slice the embryos such that they routinely result in a culture that demonstrates viability over a period of several days, and most importantly, develops in an age-specific manner. For mid-gestation embryos, this includes the normal outgrowth of spinal nerves from the spinal cord and the dorsal root ganglia to their targets in the periphery and the proper determination of skeletal and muscle tissue. In this work, we present a method for processing whole embryos of embryonic day (E) E10 to E12 into 300 - 400 micrometer slices for cultivation in a standard tissue culture incubator, which can be studied for up to two days after slice preparation. Critical for the success of this approach is the use of a vibratome to slice each agarose-embedded embryo. This is followed by the cultivation of the slices upon Millicell culture membrane inserts placed upon a small volume of medium, resulting in an interface culture technique. One litter with an average of 7 embryos routinely produces at least 14 slices (2-3 slices of the forelimb region per embryo), which varies slightly due to the age of the embryos as well as to the thickness of the slices. About 80% of the cultured slices show nerve outgrowth, which can be measured througout the culturing period(2). Representative results using the tauGFP mouse line are demonstrated.

Rac GTPase-activating Protein (Rac GAP) α1-Chimaerin Undergoes Proteasomal Degradation and Is Stabilized by Diacylglycerol Signaling in Neurons

α1-Chimaerin is a neuron-specific member of the Rho GTPase-activating protein family that selectively inactivates the small GTPase Rac. It is known to regulate the structure of dendrites and dendritic spines. We describe here that under basal conditions α1-chimaerin becomes polyubiquitinated and undergoes rapid proteasomal degradation. This degradation is partly dependent on the N-terminal region that is unique to this isoform. Mimicking diacylglycerol (DAG) signaling with a phorbol ester stabilizes endogenous α1-chimaerin against degradation and causes accumulation of the protein. The stabilization requires phorbol ester binding via the C1 domain of the protein and is independent of PKC activity. In addition, overexpression of a constitutively active Rac1 mutant is sufficient to cause an accumulation of α1-chimaerin through a phospholipase C-dependent mechanism, showing that endogenous DAG signaling can also stabilize the protein. These results suggest that signaling via DAG may regulate the abundance of α1-chimaerin under physiological conditions, providing a new model for understanding how its activity could be controlled.