细胞生物学

Growing evidences suggest that peritubular capillaries pericytes are the main source of scar-forming myofibroblasts during chronic kidney disease (CKD), as well as early phases of acute kidney injury (AKI). In a swine model of sepsis and I/R (Ischemia Reperfusion) injury-induced AKI we demonstrated that renal pericytes are able to transdifferentiate toward α-SMA⁺ myofibroblasts leading to interstitial fibrosis. Even if precise pericytes identification requires transmission electron microscopy and the co-immunostaining of several markers (i.e., Gli, NG2 chondroitin sulphate proteoglycan, CD146, desmin or CD73) and emerging new markers (CD248 or TEM1, endosialin), previous studies suggested that PDGFR-β could be used as marker for renal pericytes characterization. Recently, double immunofluorescence staining of PDGFR-β and α-SMA was performed to identify the damage activated pericytes (PDGFR-β⁺/α-SMA⁺ cells) in the early phase of fibrosis development. Our data highlighted the crucial role of renal pericytes in the physiopathology of sepsis and I/R associated AKI. In this protocol, we describe the procedure for double immunofluorescence staining of PDGFR-β and α-SMA in swine Formalin-Fixed Paraffin-Embedded (FFPE) kidney biopsies and the method for image analysis and quantification.

Endocytosis is an intracellular trafficking pathway that occurs in nutrient uptake, signal transduction and reconstruction of cell polarity and is conserved in eukaryotic cells. In fungi, endocytosis plays crucial roles in the physiology of hyphal growth and pathogenicity. vidence for endocytosis in filamentous fungi is detected by the membrane-selective dyes FM4-64. Cells of a range of filamentous fungal species readily take up these dyes. However, the method for endocytosis detection has not been well established in Magnaporthe oryzae. Here, we provide a protocol for tracking endocytosis in Magnaporthe oryzae.

Major Histocompatibility Complex (MHC) tetramers have been used for two decades to detect, isolate and characterize T cells specific for various pathogens and tumor antigens. In the context of Human Immunodeficiency Virus (HIV) infection, antigen-specific CD8⁺ T cells have been extensively studied ex vivo, as they can be readily detected by HIV peptide-loaded MHC class I tetramers. In contrast, the detection of HIV-specific CD4⁺ T cells has proven more challenging, due to the intrinsically lower clonal expansion rates of CD4⁺ T cells, and to the preferential depletion of HIV-specific CD4⁺ T cells in the course of HIV infection.

In the following protocol, we describe a simple method that facilitates the identification of CD4⁺ T cells specific for an HIV-1 capsid epitope using peptide-loaded MHC class II tetramers. Tetramer labeled CD4⁺ T cells can be analyzed for their cell surface phenotype and/or FACS-sorted for further downstream applications. A key point for successful detection of specific CD4⁺ T cells ex vivo is the choice of a peptide/MHC II combination that results in high-affinity T Cell Receptor (TCR) binding (Benati et al., 2016). A second key point for reliable detection of MHC II tetramer-positive cells is the systematic use of a control tetramer loaded with an irrelevant peptide, with the sample and control tubes being processed in identical conditions.

Accumulation of metals in plant tissues, and occasionally, different cells of the same tissue, may be highly non-uniform (Seregin and Kozhevnikova, 2008). Easy-to-use histochemical methods may greatly help to investigate the distribution and accumulation of metals within and among plant tissues, and also provide information on their subcellular localization (Seregin and Kozhevnikova, 2011). The histochemical techniques of zinc (Zn) visualization are based on the formation of the blue-colored complex of Zn with the metallochrome indicator Zincon (C₂₀H₁₅N₄NaO₆S), or the green-fluorescent complex with Zinpyr-1 (C₄₆H₃₆Cl₂N₆O₅) (Seregin et al., 2011; Seregin and Kozhevnikova, 2011). A method for histochemical Zn detection in plant tissues using Zinpyr-1 was first proposed by Sinclair et al. (2007), and later modified by Seregin et al. (2011), and Seregin and Kozhevnikova (2011). Histochemical data supplement the results of quantitative analysis, thus allowing a detailed study of the distribution, accumulation, and translocation pathways of Zn within the plant, which are important topics in modern plant physiology. These histochemical techniques have been successfully applied in different plant species, for example Zea mays (Seregin et al., 2011), Noccaea caerulescens and Thlaspi arvense (Kozhevnikova et al., 2014a), Capsella bursa-pastoris and Lepidium ruderale (Kozhevnikova et al., 2014b), in which Zn was detected in different root and shoot tissues. Here, we present the full staining protocols for these methods, developed or modified in our lab (Seregin and Kozhevnikova, 2011; Kozhevnikova et al., 2014a; Kozhevnikova et al., 2014b).

Calcium mobilization assay is a cell-based second messenger assay to measure the calcium flux associated with Gq-protein coupled receptor activation or inhibition. The method utilizes a calcium sensitive fluorescent dye that is taken up into the cytoplasm of most cells. In some cell lines in which organic-anion transporters are particularly active (e.g. CHO, HeLa), addition of probenecid, an inhibitor of anion transport, is required for retention of this dye in the cells. The dye binds the calcium released from intracellular store and its fluorescence intensity increases. The change in the fluorescence intensity is directly correlated to the amount of intracellular calcium that is released into cytoplasm in response to ligand activation of the receptor of interest. This protocol can be applied to most mammalian cell lines expressing both endogenous and transiently/stably transfected receptors. The method is sensitive enough to be used for low-expressing systems or high throughput screening of target of interest.
Note: The method does not differentiate the Ca²⁺ mobilization induced by Gqα from the Ca²⁺ mobilization induced by Gβγ.

DiOC₂ (Novo et al., 2000) exhibits green fluorescence in all bacterial cells, but the fluorescence shifts towards red emission as the dye molecules self associate at the higher cytosolic concentrations caused by larger membrane potentials. Proton ionophores such as CCCP destroy membrane potential by eliminating the proton gradient. The magnitude of membrane potentials varies with different bacterial species. For many gram-positive species, including Staphylococcus aureus and Micrococcus luteus, the red:green ratio tends to vary with the intensity of the proton gradient while in many gram-negative bacteria such as Escherichia coli and Salmonella choleraesuis, the response of the dye does not appear to be proportional to proton gradient intensity. Mycobacterium tuberculosis itself is a difficult organism to work with because of its rigid cell wall.

Mycobacterium tuberculosis (MTB) is the bacterial pathogen responsible for tuberculosis, a human pulmonary infectious disease. Mycobacterium bovis (BCG) is the causative agent of tuberculosis in cattle, and is often used as the vaccine stain in humans. Specific recipes and methods for culture of MTB and BCG are described in this protocol.