Mounting live cells attached to coverslips for microscopy

Evidence of defined temporal expression patterns that lead a gram-negative cell out of dormancy

Many bacterial species are capable of forming long-lived dormant cells. The best characterized are heat and desiccation resistant spores produced by many Gram-positive species. Less characterized are dormant cysts produced by several Gram-negative species that are somewhat tolerant to increased temperature and very resistant to desiccation. While there is progress in understanding regulatory circuits that control spore germination, there is scarce information on how Gram-negative organisms emerges from dormancy. In this study, we show that R. centenum cysts germinate by emerging a pair of motile vegetative cells from a thick cyst cell wall coat ~ 6 hrs post induction of germination. Time-lapse transcriptomic analysis reveals that there is a defined temporal pattern of gene expression changes during R. centenum cyst germination. The first observable changes are increases in expression of genes for protein synthesis, an increase in expression of genes involved in the generation of a membrane potential and the use of this potential for ATP synthesis via ATPase expression. These early events are followed by expression changes that affect the cell wall and membrane composition, followed by expression changes that promote chromosome replication. Midway through germination, expression changes occur that promote the flow of carbon through the TCA cycle to generate reducing power and parallel synthesis of electron transfer components involved in oxidative phosphorylation. Finally, late expression changes promote the synthesis of a photosystem as well as flagellar and chemotaxis components for motility.

Modified Cajal's trichrome stain as a diagnostic aid in the study of epithelial pathology

BACKGROUND

Diagnosis of initial epithelial pathology maybe difficult in Squamous Cell Carcinoma (SCC), Carcinoma In Situ and other atypical epithelial malignancies, under routine Haematoxylin and Eosin (H and E) stain. The detection of minor basement membrane alterations in doubtful cases is both time consuming and confusing.

AIMS

To evaluate efficacy of Modified Cajal's Trichrome Stain (CTS) in relation to Haematoxylin and Eosin for study of epithelial dysplasia, carcinoma in situ, micro invasive SCC, frank SCC, and SCC in lymph nodes.

MATERIALS AND METHODS

Formalin-fixed, paraffin-embedded tissue blocks of mild epithelial dysplasia (n = 2), moderate epithelial dysplasia (n = 2), severe epithelial dysplasia (n = 4), carcinoma in situ (n = 1), micro-invasive SCC (n = 4), verrucous carcinoma (n = 1), and frank OSCC (n = 5) were stained with CTS and H&E. The sections were compared based on set histopathological criteria.

RESULTS AND CONCLUSION

In SCC cases stained with CTS, invasion into connective tissue and keratin pearls were strikingly evident. Depth of invasion could be more accurately determined. Tumour cells in lymph node were intensely contrasted and easily discernible. Thus, CTS is a good differential stain, clearly delineating the epithelial elements from the connective tissue elements visually. This helps in tracing the basement membrane very clearly. It is an economic, rapid and easy to use method which cannot replace Haematoxylin and Eosin stain in cancer diagnosis, but can definitely be used adjunctive to it. Prompt diagnosis is crucial to effective treatment, and this stain assists in early and rapid diagnosis of cancer.

Live-cell imaging

It would be hard to argue that live-cell imaging has not changed our view of biology. The past 10 years have seen an explosion of interest in imaging cellular processes, down to the molecular level. There are now many advanced techniques being applied to live cell imaging. However, cellular health is often under appreciated. For many researchers, if the cell at the end of the experiment has not gone into apoptosis or is blebbed beyond recognition, than all is well. This is simply incorrect. There are many factors that need to be considered when performing live-cell imaging in order to maintain cellular health such as: imaging modality, media, temperature, humidity, PH, osmolality, and photon dose. The wavelength of illuminating light, and the total photon dose that the cells are exposed to, comprise two of the most important and controllable parameters of live-cell imaging. The lowest photon dose that achieves a measureable metric for the experimental question should be used, not the dose that produces cover photo quality images. This is paramount to ensure that the cellular processes being investigated are in their in vitro state and not shifted to an alternate pathway due to environmental stress. The timing of the mitosis is an ideal canary in the gold mine, in that any stress induced from the imaging will result in the increased length of mitosis, thus providing a control model for the current imagining conditions.

Thymoquinone inhibits autophagy and induces cathepsin-mediated, caspase-independent cell death in glioblastoma cells

Glioblastoma is the most aggressive and common type of malignant brain tumor in humans, with a median survival of 15 months. There is a great need for more therapies for the treatment of glioblastoma. Naturally occurring phytochemicals have received much scientific attention because many exhibit potent tumor killing action. Thymoquinone (TQ) is the bioactive compound of the Nigella sativa seed oil. TQ has anti-oxidant, anti-inflammatory and anti-neoplastic actions with selective cytotoxicity for human cancer cells compared to normal cells. Here, we show that TQ selectively inhibits the clonogenicity of glioblastoma cells as compared to normal human astrocytes. Also, glioblastoma cell proliferation could be impaired by chloroquine, an autophagy inhibitor, suggesting that glioblastoma cells may be dependent on the autophagic pathway for survival. Exposure to TQ caused an increase in the recruitment and accumulation of the microtubule-associated protein light chain 3-II (LC3-II). TQ also caused an accumulation of the LC3-associated protein p62, confirming the inhibition of autophagy. Furthermore, the levels of Beclin-1 protein expression were unchanged, indicating that TQ interferes with a later stage of autophagy. Finally, treatment with TQ induces lysosome membrane permeabilization, as determined by a specific loss of red acridine orange staining. Lysosome membrane permeabilization resulted in a leakage of cathepsin B into the cytosol, which mediates caspase-independent cell death that can be prevented by pre-treatment with a cathepsin B inhibitor. TQ induced apoptosis, as determined by an increase in PI and Annexin V positive cells. However, apoptosis appears to be caspase-independent due to failure of the caspase inhibitor z-VAD-FMK to prevent cell death and absence of the typical apoptosis related signature DNA fragmentation. Inhibition of autophagy is an exciting and emerging strategy in cancer therapy. In this vein, our results describe a novel mechanism of action for TQ as an autophagy inhibitor selectively targeting glioblastoma cells.

Immunolabeling of cells grown attached to a substratum or in suspension with actin antibodies

Actin is a major component of all eukaryotic cells and is highly conserved across species. The different isoforms of actin show a very high degree of homology, and almost all actins bind cytochalasins, phallotoxins, and DNase I. Actin is important for maintaining cell shape and for myosin-based movements in cells. In addition, the actin cytoskeleton is involved in localization of other molecules in the cytoplasm and in cellular compartmentalization. Polyclonal and monoclonal antibodies with different specificities are commercially available for labeling actin-containing structures in cells. This article describes a protocol for immunolabeling actin that works well for cells grown in tissue culture as monolayers and for cells grown in suspension cultures that can be attached to polylysine-coated coverslips.

Labeling the endoplasmic reticulum with DiO-C6(3) for imaging

The eukaryotic cell has evolved to compartmentalize its functions and transport various metabolites among cellular compartments. Therefore, in cell biology, the study of organization and structure/function relationships are of great importance. The endoplasmic reticulum is a highly convoluted, single membrane that is continuous with the outer nuclear membrane and is believed to form a contiguous closed sac within the cell cytosol. Although a probe specific for the endoplasmic reticulum currently does not exist, the DiO-C(6)(3) probe, a cationic dye, is an effective label because of the distinctive intracellular morphology of the endoplasmic reticulum that distinguishes it from other intracellular organelles. This protocol describes the labeling of the endoplasmic reticulum with DiO-C(6)(3).

Labeling cytoskeletal F-actin with rhodamine phalloidin or fluorescein phalloidin for imaging

The eukaryotic cell has evolved to compartmentalize its functions and transport various metabolites among cellular compartments. Therefore, in cell biology, the study of organization and structure/function relationships is of great importance. The cytoskeleton is composed of a series of filamentous structures, including intermediate filaments, actin filaments, and microtubules. Immunofluorescent staining has been most frequently used to study cytoskeletal components. However, it is also possible to fluorescently label isolated cytoskeletal proteins and either microinject them back into the cell or add them to fixed, permeabilized cells. Alternatively, it is possible to use the mushroom-derived fluorescinated toxins, phalloidin or phallacidin, to label F-actin of the cytoskeleton, as is described in this article. Phalloidin is available labeled with different fluorophores. The choice of the specific fluorophore should depend on whether phalloidin labeling for actin is part of a double-label experiment. In most cells, the abundance of actin filaments should provide a very strong signal. In double-label experiments, the fluorophore should be chosen to take this into account. In general, rhodamine labels are more resistant to photobleaching and can be subjected to the longer exposures required for finer structures.

Labeling pinocytotic vesicles and cytoplasm with fluorescent dextrans or ficolls for imaging

The eukaryotic cell has evolved to compartmentalize its functions and transport various metabolites among cellular compartments. Therefore, in cell biology, the study of organization and structure/function relationships is of great importance. Dextran, a high-molecular-weight poly-D-glucose, and ficoll, a synthetic polymer of epichlorhydrin and sucrose, are electroneutral, hydrophilic polysaccharides whose size can be varied. This variability in size coupled with their membrane impermeability can make them useful for studying fluid-phase pinocytosis, the size of membrane pores (e.g., nuclear membrane pores), or the environmental conditions and size of a cell compartment. This article presents a method for labeling live or fixed cells with substituted forms of dextran or ficoll attached to a fluorescent conjugate. In the event that the desired probe is not available commercially, this article also provides a method for covalently attaching a fluorophore to substituted polysaccharide.