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At least 1,621 records · Page 90Linked to original sources
PubMed1999

Lymphocyte dynamics in the pulmonary microenvironment: implications for the pathophysiology of pulmonary sarcoidosis.

It is generally accepted that lymphocytes play a role in sarcoidosis. Lymphocyte numbers and in particular certain subsets are increased in the bronchoalveolar lavage fluid, and these parameters have been used as indicators for prognosis. To understand the pathophysiology of sarcoidosis the localisation and kinetics of lymphocytes in the normal lung have to be known. Lymphocytes are found in different compartments of the lung: the pulmonary vascular bed with the marginal lymphocyte pool, intraepithelial lymphocytes, the lamina propria of the bronchial tree, at a young age and under certain pathological conditions the bronchus-associated lymphoid tissue, the interstitial lymphocyte pool and the lymphocytes in the bronchoalveolar space as recovered by bronchoalveolar lavage. The lymphocyte subsets differ in these compartments. The number and subset composition are influenced by the balance of immigration, regulated by adhesion molecules, local proliferation, apoptosis and migration. In sarcoidosis lymphocyte proliferation and cell death in the bronchoalveolar space are increased several fold in the lung. More studies on regulatory factors of lymphocyte kinetics are needed in the lung of sarcoidosis patients before new therapeutic strategies can be tested.

Apoptosis↗
PubMed2000

The influence exerted by a restricted phospholipid microenvironment on the expression of tissue factor activity at the cell plasma membrane surface.

Phosphatidylserine (PhtdSer) is an anionic aminophospholipid necessary for the development of optimal tissue factor (TF) activity at the cell surface. This study investigates the implication of a restricted lipid environment with respect to PhtdSer availability on TF expression and activity. K562 cells, showing a reduced ability to externalize PhtdSer, were transfected with human TF cDNA. PhtdSer exposure and TF activity were examined in transfected cells and compared to monocytic THP-1 cells expressing constitutive and inducible TF or megakaryocytic HEL cells showing a high PhtdSer externalization potency. TF expression was evidenced by flow cytometry and its activity measured using functional assays. PhtdSer exposure was monitored by enzymatic prothrombinase assay. One clone (DC9) expressed a stable amount of TF antigen without global modification of its membrane status. Despite a noticeable TF expression level, clone DC9 presented only a weak TF activity even after ionophore stimulation. The apparent Km, relative to factor X (FX) activation by TF-factor VIIa (FVIIa) complex, was 335 nM versus 70 nM for THP-1 cells. The velocity of the reaction was found 3-fold slower in DC9 than THP-1 cells. Ionophore treatment resulting in slightly enhanced amounts of available PhtdSer abolished this difference. The DC9 clone appears suitable for further investigations on the biology of TF expressed at the surface of cells where the contribution of PhtdSer is significantly attenuated. Such cells should enable further assessment of the role of TF as a receptor coupled to intracellular signaling pathways and its fate during apoptotic cell death.

Antigens, Surface↗
PubMedDate not supplied

[Regularities in the kinetic of photoactivation of lactate dehydrogenase by the action of UV light in different microenvironment].

The kinetics of photoinactivation of cardiac (H4) and muscular (M4) isoforms of lactate dehydrogenase irradiated by UV light (240-390 nm) in the free form and in the presence of sodium azide, D-mannitol, and serotonin was studied. It was shown that the decrease in the catalytic activity of both enzymes can be described by the kinetics of the first-order monomolecular reaction. The inactivation rate constant of lactate dehydrogenase M4 is considerably higher than that of lactate dehydrogenase H4, indicating a greater photochemical lability of the isoform M4. It was shown that sodium azide has a different protective action on the proteins studied. The irradiation of the muscular isoform in the presence of serotonin and D-mannitol did not change the character of the "dose-effect" curve and only led to a decrease in the photoinactivation rate constant of the protein.

Animals↗
PubMedDate not supplied

Immunocytochemical detection of the homeobox B3, B4, and C6 gene products within the human thymic cellular microenvironment.

The homeobox (HOX) was originally described as a conserved DNA motif of about 180 base pairs. The protein domain encoded by the homeobox, the homeodomain, is thus about 60 amino acids long. The homeodomain is a DNA-binding domain, and many homeobox genes have now been shown to bind to DNA and regulate the transcription of other genes. Thus homeodomain proteins are basically transcription factors, most of which play a role in development. The homeobox genes seem to represent another class of oncofetal antigens involved in both normal development and carcinogenesis, as well as tumor progression. The expression pattern of three homeobox gene products (HOX-B3, HOX-B4, and HOX-C6) was examined immunocytochemically in human thymuses of different ages and developmental stages (prenatal: 16 weeks and postnatal: 3 years, 5 years, and 21 years) employing an indirect alkaline phosphatase conjugated antigen detection technique on formalin-fixed, paraffin-embedded tissue sections. The immunoreactivity was located in the thymic RE cellular network (cortical and medullar), showing different intensity (+3 to +4 or 50% to 90% and over 90% in the prenatal thymic tissue and +2 to +3 or 50% to 90% during the three different postnatal stages). Intense expression was identified in the thymic medulla, including very strong immunoreactivity in the immigrating, committed hematopoietic stem cells (HSCs) present within the interlobular connective tissue (ICT). Strong presence of the HOX-B3 and HOX-B4 proteins was detected in the thymic Hassall's bodies (HBs), suggesting an intensive functional activity of the RE cells present within these unique formations within the thymic medulla. The precise role of these and other HOX gene products in the various steps of intrathymic T lymphopoieis should be elucidated through further basic molecular biological research.

Adult↗
PubMed1975

Evidence for an abnormal microenvironment in the thymus of New Zealand black mice.

The proliferative response of NZB and DBA/2 thymocytes and spleen cells to allogeneic cells and mitogens was studied in intact and lethally irradiated bone marrow-repopulated syngeneic recipients. The major findings were complete recovery of function in NZB spleen cells and premature recovery in thymocytes compared to the control DBA/2 strain. This recovery was not influenced by the administration of thymosin to the recipients, and was not due to functional thymocytes present in the donor marrow inoculum. These results suggest normal or increased support of T cell differentiation by the radioresistant thymus in 4-month-old NZB mice. Thymic epithelial cell products regulating T cell maturation may be disordered or unbalanced but do not appear to be broadly deficient at this age.

Animals↗
PubMed1975

[Survival in gazeous phase and reconstitution "in vitro" of the natural microenvironment of alveolar macrophages].

Alveolar macrophages of guinea pigs laid on a porous membrane applied to the surface of a reservior filled with nutrient fluid, may be maintained in survival in gaseous phase. The addition of biological material obtained by centrifugation of the broncho-alveolar nutrient fluid, creates in vitro a micro-environment comparable to the physiological alveolar or bronchial environment. Examination of these macrophages under the light and electron microscopes, and study of their phagocytic and bactericidal activity, demonstrate the value of this experimental model, which opens new possibilities for research on the means of phagocytic defence of the respiratory apparatus and their disturbances by gases which pollute the atmosphere.

Air Pollutants↗
PubMed2001

Selected cell and selective microenvironment in neoplastic development.

Recent analysis of genetic alterations in human cancer points to a major role for selection in neoplastic development but provides few details about the dynamics of the process. Many such details, however, have emerged from quantitative studies of spontaneous transformation among mammalian cells in culture. The chief insight of these studies is that there is a continuous generation of variants in proliferative potential among growing cells that provides the substratum for progressive development to a frankly neoplastic state when selective growth conditions are persistently applied. Much of the selection occurs before the cells are capable of producing discrete neoplastic foci. The varied observations in cell culture draw attention to analogous features of carcinogenesis in experimental animals and the development of human cancer.

Animals↗
PubMed2000

Low dose UV-B induced modification of chromophore conformation and it's interaction with microenvironment in cyanobacterial phycobilisomes.

Phycobilisomes (Pbsomes) are the supra macromolecular pigment protein complexes of cyanobacteria. Synechococcus Pbsomes are comprised of phycocyanins (PC) and allophycocyanins (APC). Pbsomes are major light harvesting antennae and also absorb ultraviolet-B (UV-B) radiation (280-320 nm). Synechococcus Pbsomes, upon exposure to low dose of UV-B (0.28 mW cm-2) for different time intervals showed profound alteration in their steady state absorption, fluorescence excitation and emission characteristics (Sah et. al. Biochem. Mol. Biol.Int., Vol. 44, No. 2, 245-247). In the present study, we investigated the effect of low dose of UV-B on isolated Pbsome of Synechococcus. Our results demonstrate the following alterations. Absorbance at 623 nm initially showed a sharp decrease with increasing exposure time to UV-B radiation. The changes in the visible to near ultraviolet absorption and excitation ratio indicated a change in chromophore conformation, upon prolonged exposure of Pbsomes to UV-B radiation. This modification of chromophore conformation appeared to be associated with the loss of energy transfer from PC to APC. Circular dichroism spectra in the amide region showed a significant loss of the alpha helical content of Pbsomes when exposed for longer duration to UV-B. CD spectra in the visible region revealed a marked decrease in the rotational strength at 620 nm. Close monitoring of CD signals emanating in the 500 to 700 nm range further revealed that the decrease in the rotational strength was closely associated with an initial red shift in the positive CD band of Pbsomes when exposed to UV-B for short duration. However, the peak became constant over prolonged exposure to UV-B radiation and accompanied a prominent blue shoulder in the positive CD band which suggests the modification and uncoupling of the various phycocyanobilin (PCB) chromophores of the Synechococcus Pbsomes.

Bacterial Proteins↗
PubMed2000

The Hematopoietic Microenvironment: The Osteogenic Compartment of Bone Marrow: Cell Biology and Clinical Application.

The marrow stromal cells of the bone cavities are of mesenchymal origin. These cells are maintaining bone remodeling and control the differentiation of hemopoietic cells during the life span. The function of the marrow stroma is based on cells that differentiate into various subtypes that are derived from a common stem cell. Plating the bone marrow at low density, they form colonies with a fibroblast-like appearance (CFU-F). The fibroblastic colonies may differentiate to distinct cell types as fibroblasts, endothelial, osteogenic and adipocytes. Understanding of the control mechanism of these cells' differentiation is very important. We used an in vitro system from established primary cultures and continuos cell lines, MBA cells from mouse bone marrow. The MBA cells were used to study the stromal cells subtypes. Herein, we summarized the knowledge on the osteogenic cells' differentiation using the marrow-derived stromal osteogenic cells, MBA-15 and clonal lines. The characterization of cells was based on morphology, rate of cell growth, gene expression and biochemical profile. A deeper understanding of the osteogenic cells differentiation will lead to better use of the marrow stroma cells in clinical application and tissue engineering to ensure healing of bone defects or skeletal genetic diseases.

Journal Article↗
PubMedDate not supplied

[The hematopoietic stem cell and the stromal microenvironment].

The hematopoietic system is the adult cellular model in which the biology of the stem cells is the best known and may be a model for numerous other tissues. This model is theoretically based on a hierarchy of cells, which begin on a stem cell that differentiates into mature cells through a large number of cellular stages including hematopoietic progenitors. Hematopoietic stem cells have three ain properties: (1) Self-renewal capacities. However, in transplantation experiments this property is limited and may be regulated by the stem cell niche. (2) Multipotentiality. Hematopoietic stem cells are capable of differentiation towards all myeloid and lymphoid lineages. However, recent experiments suggest that, like other somatic stem cells, hematopoietic stem cells are capable

Animals↗
PubMed2002

Retinal microenvironment controls resident and infiltrating macrophage function during uveoretinitis.

PURPOSE: Macrophages infiltrating an inflamed or injured tissue undergo development of coordinated sets of properties that contribute to tissue damage, repair, and remodeling. The purpose of this study was to determine whether macrophages isolated from normal or inflamed retina are programmed to a distinct set of properties and to examine whether the development of experimental autoimmune uveoretinitis (EAU) affects macrophage function. METHODS: EAU was induced in Lewis rats, and a retina-derived macrophage-enriched population was generated by density centrifugation during the prepeak, peak, and resolution phases of the disease. Cell surface phenotype was assessed by two- and three-color flow cytometry, and function was determined in vitro by nitric oxide (NO) production, with or without further cytokine stimulation or by immunohistochemistry to determine expression of beta-glucuronidase, nitric oxide synthase (NOS)-2, and nitrotyrosine. RESULTS: Myeloid-derived cells from normal retina were programmed similar to TGF-beta-stimulated uncommitted bone-marrow-derived macrophages (BMDMs). Contrary to BMDM behavior, retina-isolated macrophages displayed distinct properties and phenotype at different phases of the disease course and remained resistant throughout, to further cytokine challenge in vitro. During peak disease, retina-isolated macrophages had characteristics of IFN-gamma/TNF-alpha primed cells (nitrotyrosine positive and NO producing). Despite equivalent numbers of macrophages during resolution, their function reverted to characteristics of TGF-beta primed cells (beta-glucuronidase positive). CONCLUSIONS: Resident retinal myeloid-derived cells are primed and are resistant to further cytokine stimulation, and, similar to macrophages derived during EAU recovery, behave operationally as though TGF-beta primed. During peak inflammation, infiltrating macrophages adapt to concurrent hierarchical Th1 T-cell response (IFN-gamma/TNF-alpha), generating NO. The results provide evidence of in vivo programming of macrophages within the retina.

Animals↗