Role Of Different Cell Types Research Articles

MITOCHONDRIA-RICH CELL SUBTYPES IN FISH GILL

The roles of different cell types involved in ion transport in the fish gill have been widely debated but it is commonly accepted that mitochondria-rich chloride cells and pavement cells play key roles in ion and acid—base transport in freshwater fish. Mitochondria-rich cells function in acid—base regulation by altering chloride and carbonate exchange, while pavement cells are currently believed to be the site of sodium uptake at the gill.Galvez and colleagues focus on the mitochondria-rich chloride cells in the freshwater trout gill. They use a novel magnetic bead separation technique to isolate different mitochondria-rich cell subtypes. The existence of these cell subtypes in fish gill had been proposed but evidence to support their existence was lacking.Different sub-types of mitochondria-rich cells in other animals have been identified by looking at the differential binding of peanut lectin agglutinin (PNA) to the apical surfaces of mitochondria-rich cell types. Galvez and colleagues adopted this technique to distinguish between subtypes of mitochondria-rich cells in the fish gill.Research on the fish gill from their lab indicates that PNA binds to mitochondria-rich chloride cells on the apical surface of the gill epithelium. Here, they use PNA binding to separate mitochondria-rich gill cells into PNA+ and PNA- populations. They identify the existence of at least two mitochondria-rich cell subtypes. The ultrastructure of the PNA+ cells was characteristic of mitochondria-rich chloride cells, whereas the PNA- cell morphology was reminiscent of pavement cells.The functional properties of these subtypes in acid—base regulation were examined by the expression of two proteins important in epithelial transport. The Na+-K+-ATPase is involved in energising both sodium and chloride uptake across the gill and the H+-ATPase provides an electrochemical gradient that drives sodium movement. The expression of these proteins under normal, acidosis and alkalosis conditions was examined.Both ATPases were expressed in the PNA+ and PNA- cell types. However, both of these proteins were expressed differently in the two subtypes during acid—base disturbances. Most notably, only the PNA- cell types responded during acidosis, by increasing expression of the H+-ATPase.The authors suggest that the site of proton excretion in gill tissue is the PNA- cells and that the PNA+ cells are analogous in function to the β-mitochondria-rich chloride cells of the mammalian kidney collecting ducts, which are responsible for base-secretion. In the mammalian kidney, there is a functional separation of mitochondria-rich cell types into acid-secreting and base-secreting cells. Separating and identifying different subtypes in the fish gill is both important and interesting to determine whether the functional separation also occurs in gill tissue.Galvez and colleagues are now hoping to clone the apical anion exchanger in the PNA+ mitochondria-rich chloride cells of the fish gill. The use of magnetic bead separation to enrich for PNA+ mitochondria-rich chloride cells should help improve the ability of cloning rare transport proteins on this cell type.

Zu allergischen Entzündungsreaktionen der Haut

A number of constitutive cutaneous cells and cells which infiltrate the skin from the circulation contribute to allergic inflammatory skin reactions. The knowledge about the roles of different cell types in allergic skin reactions has been considerably grown during the last years. This review describes functions both of keratinocytes, dermal endothelial cells and antigen-presenting cells of the skin and of skin-infiltrating T-lymphocytes. A focus is laid on skin-infiltrating T-cells since allergic eczematous skin diseases are associated with an infiltration of this cell type into the inflamed organ. The work also contains some thoughts about futural perspectives in the treatment of allergic skin diseases using immunomodulatory principles.

Differential expression of class I HDACs: Roles of cell density and cell cycle

Enzymes which affect histone acetylation status have been shown to play an important role in determining transcriptional activity in chromatin through conformational modification of its structure. Since the timely presence of such enzymes may be of critical importance, our experiments were designed to determine whether the level of expression of HDAC1 is cell cycle dependent and/or affected by a high cell density. Our results show that in mouse fibroblasts the expression of mHDAC1 is neither affected by cell cycle phases nor by cell density. In contrast, the expression of several hHDACs including hHDAC1 were affected in a cell density dependent fashion in the human prostate adenocarcinoma cell line PC3, paralleling our previously published findings in the hepatocellular carcinoma derived cell line Hep3B. Differential recruitment of HDAC mRNAs suggests that these enzymes may play unique roles in different cell types and under different environmental conditions (i.e., exposure to various cell densities and cell-cell contacts). Our study has implications for the proposed use of HDAC inhibitors in the treatment of human malignancy, highlighting issues of drug action selectivity in tissues and potential secondary effects.

Thymic stromal cells and positive selection.

The intrathymic differentiation events leading to the development and export of mature T cells tolerant to self yet capable of responding to foreign peptide antigen in the context of self-MHC are clearly both dynamic and complex. The changing phenotype of the developing thymocyte as it migrates through and interacts with the heterogeneous thymic microenvironment and the intracellular signalling events associated with such interactions are being extensively studied, yet many aspects remain poorly defined, such as the precise relationship between stromal cells and thymic selection. Positive and negative selection are crucial events in the development of T cells, leading to a diverse yet non-autoreactive immune system. A breakdown in either of these processes could lead to either a reduced T cell repertoire or the escape into the periphery of autoreactive T cells - both clearly having deleterious consequences for the health of the individual. This review aims to summarise the current status of research in thymic positive selection with emphasis on the role of different cell types and peptides.

Thymic stromal cells and positive selection

The intrathymic differentiation events leading to the development and export of mature T cells tolerant to self yet capable of responding to foreign peptide antigen in the context of self‐MHC are clearly both dynamic and complex. The changing phenotype of the developing thymocyte as it migrates through and interacts with the heterogeneous thymic microenvironment and the intracellular signalling events associated with such interactions are being extensively studied, yet many aspects remain poorly defined, such as the precise relationship between stromal cells and thymic selection. Positive and negative selection are crucial events in the development of T cells, leading to a diverse yet non‐autoreactive immune system. A breakdown in either of these processes could lead to either a reduced T cell repertoire or the escape into the periphery of autoreactive T cells – both clearly having deleterious consequences for the health of the individual. This review aims to summarise the current status of research in thymic positive selection with emphasis on the role of different cell types and peptides.

The Toll receptor family.

The Toll receptor family.

Single-cell analysis of bacteria by Raman microscopy: spectral information on the chemical composition of cells and on the heterogeneity in a culture

In the acetone–butanol (ABE) fermentation process, the utilised organisms from the group of the solventogenic Clostridia go through a complex cell-cycle. The role of different cell types in product formation is not understood in detail yet. We aim to use Raman spectroscopy to characterise the population distribution in Clostridium cultures. Cell suspensions were dried on calcium fluoride carriers. Raman spectra of single cells were obtained using a confocal Raman microscope (Dilor, Lille, France). The laser beam was focused on individual cells through the microscope objective. Spectra with good signal-to-noise ratio were obtained. Cells of different morphology, but also apparently similar cells, showed different spectra. Several cell components could be detected and varied in quantity. Compared to other methods for single-cell analysis, the new method is much more time-consuming to analyse one individual cell. However, a large amount of chemical information is obtained from each single cell in a non-destructive, non-invasive way. Raman microscopy appears to be a suitable method for studying population distributions in bacterial cultures.

Single Cell Ras-GTP Analysis Reveals Altered Ras Activity in a Subpopulation of Neurofibroma Schwann Cells but Not Fibroblasts

Neurofibromatosis type 1 (NF1) is a common genetic disorder characterized by multiple neurofibromas, peripheral nerve tumors containing mainly Schwann cells and fibroblasts. The NF1 gene encodes neurofibromin, a tumor suppressor postulated to function in part as a Ras GTPase-activating protein. The roles of different cell types and of elevated Ras-GTP in neurofibroma formation are unclear. To determine which neurofibroma cell type has altered Ras-GTP regulation, we developed an immunocytochemical assay for active, GTP-bound Ras. In NIH 3T3 cells, the assay detected overexpressed, constitutively activated K-, N-, and Ha-Ras and insulin-induced endogenous Ras-GTP. In dissociated neurofibroma cells from NF1 patients, Ras-GTP was elevated in Schwann cells but not fibroblasts. Twelve to 62% of tumor Schwann cells showed elevated Ras-GTP, unexpectedly revealing neurofibroma Schwann cell heterogeneity. Increased basal Ras-GTP did not correlate with increased cell proliferation. Normal human Schwann cells, however, did not demonstrate elevated basal Ras activity. Furthermore, compared with cells from wild type littermates, Ras-GTP was elevated in all mouse Nf1(-/-) Schwann cells but never in Nf1(-/-) mouse fibroblasts. Our results indicate that Ras activity is detectably increased in only some neurofibroma Schwann cells and suggest that neurofibromin is not an essential regulator of Ras activity in fibroblasts.

Cytokines that signal through the leukemia inhibitory factor receptor-beta complex in the nervous system.

Cytokines that signal through the leukemia inhibitory factor (LIF) receptor, such as LIF and ciliary neuronotrophic factor, have a wide range of roles within both the developing and mature nervous system. They play a vital role in the differentiation of neural precursor cells into astrocytes and can prevent or promote neuronal differentiation. One of the conundrums regarding signalling through the LIF receptor is how it can have multiple, often conflicting roles in different cell types, such as enhancing the differentiation of astrocytes while inhibiting the differentiation of some neuronal cells. Factors that can modulate signal transduction downstream of cytokine signalling, such as "suppressor of cytokine signalling" proteins, which inhibit the JAK/STAT but not the mitogen-activated protein kinase pathway, may therefore play an important role in determining how a given cell will respond to cytokine signalling. This review discusses the general effects of cytokine signalling within the nervous system. Special emphasis is placed on differentiation of neural precursor cells and the role that regulation of cytokine signalling may play in how a given precursor cell responds to cytokine stimulation.

Tissue distribution of primary metabolism between epidermal, mesophyll and parenchymatous bundle sheath cells in barley leaves

This paper originates from a presentation at the International Conference on Assimilate Transport and Partitioning, Newcastle, NSW, August 1999 In order to investigate the roles of different cell types, metabolite compartmentation in barley (Hordeum vulgare L.) leaf tissue was mapped at the single-cell level, using single-cell sampling and analysis (SiCSA) techniques. The partitioning of recently fixed photoassimilate was investigated for the first time at single-cell resolution, using BAMS (biological accelerator mass spectroscopy) for precise measurement of 14C in femtomole quantities. The data obtained by BAMS qualitatively reflect concentrations of sugars in different cell types measured by SiCSA. Calculation of 14C-specific activities showed that the radioactive label saturated the mesophyll and parenchymatous bundle sheath (PBS) pools within the 45-min labelling period. During the photoperiod, sucrose concentration increased to 200 mM in mesophyll cells. The concentration of malate also increased during the photoperiod in mesophyll and PBS cells. Epidermal cells contained very low concentrations of sugar but high concentrations of malate (120–180 mM) and did not show significant diurnal changes. Accumulation of sugars and fructan synthesis could be induced in mesophyll and PBS cells by reduced export of sugars from leaves or, alternatively, when sugars were supplied from excised leaf blade bases immersed in a sucrose solution in the dark. The epidermis accumulated additional malate in step with the accumulation of sugar by the mesophyll/PBS cells during the long-term reduction of export. Immunolocalisation of Rubisco and cytochrome oxidase proteins was used to analyse the distribution of enzymes of photoassimilation and respiration between functionally different cells in mature leaves of barley.

The endothelin system in human and monkey ovaries: in situ gene expression of the different components.

The endothelin system is composed of three endothelin isoforms (ET-1, ET-2, and ET-3), the endothelin receptors ETA and ETB, and the endothelin-converting enzyme (ECE). Besides having a major vasoactive role, endothelins have roles in different cell types at a local level. We investigated the presence of the different components of the endothelin system in primate ovaries. Human ovaries and gonadotropin-stimulated monkey ovaries were studied using immunohistochemistry for endothelin, and in situ hybridization with probes for ET-1, ET-2, ET-3, ETA and ETB receptors, and ECE. ET-1 and ETA receptors were detected in endothelial cells and vascular smooth muscle cells, respectively, in stromal vessels adjacent to follicles and corpora lutea. ETB receptors and ET-1 were found in the endothelial cells of capillaries of corpora lutea. ECE was present in internal theca cells of secondary, de Graaf, atretic follicles, and in luteinized granulosa cells of the corpora lutea. The endothelin system components are present in or around the follicles of human and monkey ovaries. Although the components are not expressed in the same cell types, they are synthesized, mainly in follicles, by cells that are in close proximity. Thus, the endothelin system could act in a paracrine manner. ECE expression in steroid-producing cells changes its compartmentalization during follicle maturation.

Matrix metalloproteinases and their inhibitors

The progressive breakdown of connective tissues of the articular joints is a major feature of the arthritides and becomes an irreversible process leading to permanent loss of function and disability. Recent research has been directed at the analysis of the relative roles of different cell types and the different classes of proteinases that they produce in such deg-radative processes. It is known that proteinases of all mechanistic classes have the potential to degrade individual connective tissue macromolecules in vitro, but the elucidation of their precise role in vivo is more difficult. The current view is that the initial step in the breakdown of the matrix in both physiological and pathological situations is an extracellular process, often involving matrix metalloproteinases (MMPs) which function at neutral pH. In certain special environments, cysteine proteinases with more acidic pH optima are also active and in rapid resorption or inflammatory events, serine proteinases are released by invading cells. Mechanical disruption and the presence of free radicals can also augment the degradative process. Matrix fragments are subsequently phagocytosed for processing intracellularly within the lysosomal system. These processes are normally tightly regulated by a complex interplay of cell-cell and cell-matrix interactions involving the production of proteinases, activators and inhibitors and other regulatory molecules. The accelerated breakdown of connective tissue seen in diseases such as rheumatoid arthritis may be due largely to a breakdown in these regulatory mechanisms.

Visualization of the endogenous NF-kappa B p50 subunit in the nucleus of follicular dendritic cells in germinal centers.

NF-kappa B, a 50 kDa/65 kDa (p50/p65) heterodimer, is a ubiquitous transcription factor involved in the positive regulation of various immune genes. The aim of this study was to determine whether NF-kappa B is related to a particular cell type and/or differentiation step during immunopoiesis. Using in situ hybridization on sections from non HIV hyperplastic lymph nodes, we found that the gene of the 105 kDa precursor of p50 was overexpressed in the light zone of germinal centers, with a network aspect, which suggested the involvement of follicular dendritic cells (FDC). By immunohistochemistry, p50 protein was detected in the cytoplasm and nucleus of FDC, confirming the involvement of FDC. Furthermore, p50 protein was detected in the cytoplasm of all lymphocytes. Thus, we focused our study on isolated FDC clusters from normal tonsils. As showed on tissue sections, we detected the p50 in both cytoplasm and nucleus of FDC. Nuclei of lymphocytes from FDC clusters were negative. We next studied p65 and c-Rel protein expression in FDC clusters. p65 was detected in the cytoplasm of FDC, whereas nuclei were negative. Furthermore, p65 was detected in the nuclei of some lymphocytes. c-Rel protein was detected only in the cytoplasm of lymphocytes and not in the nucleus and cytoplasm of FDC. Our results indicated that, in the context of T cell-dependent B cell immunopoiesis occurring in FDC clusters, p50 is mainly related to FDC with a massive overexpression in the nuclei, whereas p65 is expressed in a scattered manner in the nuclei of lymphocytes and c-Rel protein exclusively in the cytoplasm of lymphocytes from FDC clusters. These results suggested that the two subunits of NF-kappa B and the c-Rel protein have different roles in different cell types during B cell immunopoiesis.

Differential distribution of cellular forms of β-amyloid precursor protein in murine glial cell cultures

The production and localization of cell-associated forms of β-amyloid precursor protein (APP) of Alzheimer's disease was investigated in primary cultures of mouse glial cells. In both oligodendrocytes and astrocytes, immunofluorescence staining with an antibody against the car☐y terminus of APP revealed an intense cytoplasmic immunoreactivity. Immunoblotting of the cell extracts detected differences in the composition of APP between oligodendrocytes and astrocytes, notably the abundance of 107 kDa subtype in oligodendrocytes. Differences in immunoblot patterns were also noted between two buffer-insoluble, membrane-rich subcellular fractions of the glial cells, nuclear-mitochondrial and microsomal; the 119 kDa APP was enriched in the former, whereas the 73 and 115 kDa APPs in the latter. The results suggest that each APP subspecies may play a distinct functional role in different cell types and subcellular fractions.

Developmental changes of three phosphoinositide-specific phospholipase C isozymes in the rat nervous system

Developmental changes of 3 phosphoinositide-specific phospholipase C isozymes (PI-PLC-β, PI-PLC-γ and PI-PLC-δ) in the rat nervous system were studied by immunohistochemical and immunochemical methods. PI-PLC-γ immunoreactivity was intensely expressed in the radial fibers from the late fetal to early newborn stages, while weaker PI-PLC-β reaction was also demonstrated in these structures. PI-PLC-β and PI-PLC-γ immunoreactivity appeared in neurons of various regions after the first postnatal week and then increased to the adult stage. Bergmann glia and some astrocytes also showed weak immunoreactivity for both isozymes from the newborn stage, while such immunoreactive astrocytes were relatively restricted in distribution in the white matter and hippocampus at the adult stage. PI-PLC-δ immunoreactivity appeared in astrocytes of entire cerebral regions from the second postnatal week, although weak antigenicity was also present in some neurons. Immunoblot analysis revealed that the immunoreactivities of 3 PI-PLC isozymes were present in both fetal and adult brains, with strong reactions of PI-PLC-β and PI-PLC-δ in adult brain and that of PI-PLC-γ in fetal brain. These results suggest that each PI-PLC isozyme plays important roles in different cell types in the course of their differentiation, and that some PI-PLC isozymes, especially PI-PLC-γ, may be involved in cellular division and growth during the histogenesis of the central nervous system.

Prevention of primary simian adenovirus type 7 (SA7) tumors in hamsters by adoptive transfer of lymphoid cells: role of different cell types.

Malignant neoplasms in general acquire neo-antigens, usually called tumor-specific transplantation antigen (TSTA). Chemically induced tumors usually exhibit antigens unique to each tumor, whereas tumors induced by a virus share a common antigen specific for that virus regardless of the histological type of tumor or host species in which the tumor was induced (1–3). These TSTA invoke an immune response, mainly of cell-mediated type. The immune control or progressive growth of the tumor depends upon many factors including strength of the cellular immune response (degree of sensitization of lymphoid cells), “sneaking through” or appearance of serum blocking factor (1, 3–5), and suppressor cells (6–8). It has generally been accepted that thymus-dependent lymphocytes (T) are primarily responsible for rejection of tumors (9–15). There is considerable evidence that macrophages also contribute an important effector mechanism against tumors (16). Recently, natural killer (NK) cells are also thought to be involved in tumor surveillance (17–19). Most of the studies of effector mechanisms of tumor immunity have been carried out in vitro, using various cytotoxicity assays. To assess the role of in vivo cell-mediated immune responses in tumor immunity, two main approaches usually have been used. One consisted of studying the influence of immuno-suppression (x-irradiation, thymectomy, anti-lymphocyte serum) on the development of tumors (20–24). The alternate approach is to augment cellular immune responses either through non-specific stimulation such as Bacillus Calmette-Guerin (BCG), Corynebacterium parvum (CP), poly I:C, etc. (25–28), or through adoptive transfer of specifically sensitized lymphoid cells (29–31).

Analysis of the role of different cell types in the genetic regulation of antibody production to the thymus-independent synthetic polypeptide poly (DTyr, DGlu)-poly (DPro)--poly (DLys).

The immune response potential of mice to the thymus-independent synthetic polypeptide poly (DTyr, DGlu)-poly(DPro)--poly(DLys)[D(T,G)-Pro--L] is genetically regulated. The defect in the ability of low responder mice to mount an immune response to this antigen appears to be expressed in their B cell population since the presence of thymocytes, or addition of "educated T cells" or supernatant of T cells after stimulation with the antigen neither enhanced, nor suppressed the level of antibodies produced in both low and high responder mice. Low responsiveness could not be enhanced either by stimulation of macrophages or by injection of poly(A) - poly(U) in contrast to the significant effect of these agents on low responses to the thymus-dependent poly(LTyr, LGlu)-poly(LPro)--poly(LLys) [L(T,G)-Pro--L]. These results suggest that macrophages do not participate in the limiting step, or are not involved at all, in antibody production towards the thymus-independent polypeptide. The antibodies produced in response to D(T,G)-Pro--L were found to be mainly of the 7 S class. T cells are not required for the production of mercaptoethanol resistant antibodies to this immunogen since they were found in intact mice as well as in T cell depleted animals.

An electron microscopic study of the formation and structure of the periostracum in Astarte (Bivalvia)

An electron microscopic study of the outer and middle folds of the mantle edge of Astarte castanea reveals the fine-structural details of the cells which are involved in the formation of the periostracum. There are four types of cells in the outer fold whereas there is only one type in the middle fold. The role of different cell types in the formation of the periostracum has been discussed. The periostracum originates in the intercellular space between the basal cell of the outer fold and the first cell of the middle fold. Even at the point of origin it consists of two outer membranous layers and the inner dark homogeneous layer. The fibrous translucent layer, which is the third layer of the fully mature periostracum, does not appear until the young periostracum has moved down the periostracal groove at the level of the third cell. As the periostracum matures, the two membranous layers remain remarkably constant in width, whereas the two inner layers, dark homogeneous and fibrous translucent, increase in thickness. Scanning electron microscopy and thin sectioning reveal that the fully mature periostraca of A. castanea and A. elliptica appear uniformly pitted, but the nature of the pits between the two species is different. The fibrils of the fibrous layer show either uniform or random arrangements, depending on the region. It is the innermost part of the fibrous layer of the periostracum that provides the nuclei for calcification.