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PubMed1982

Formation of IgE-binding factors by rat T lymphocytes. VI. Cellular mechanisms for the formation of IgE-potentiating factor and IgE-suppressive factor by antigenic stimulation of antigen-primed spleen cells.

Analysis of cellular mechanisms of formation of IgE-binding factors by KLH-primed spleen cells revealed that the presentation of KLH to KLH-primed T cells by adherent cells resulted in the formation of lymphokines that in turn stimulated unprimed lymphocytes to form IgE-binding factors. Lymphokines released from KLH-alum-primed spleen cells induced normal lymphocytes to form IgE-potentiating factors, whereas those released from KLH-CFA-primed spleen cells induced the formation of IgE-suppressive factors. Fractionation of the lymphokines from KLH-primed spleen cells and analysis of cell sources of the lymphokines revealed that multiple factors are involved in the selective formation of one or the other IgE-binding factors. Thus, KLH-alum primed splenic T cells from "inducers" of IgE-binding factors and glycosylation-enhancing factors upon antigenic stimulation, and these factors in combination stimulate unprimed W 3/25+ Fc gamma R+ T cells to form IgE-potentiating factors. Antigenic stimulation of KLH-CFA-primed T cells results in the formation of the "inducers" and glycosylation-inhibiting factors, and these two lymphokines collectively stimulate unprimed W 3/25+ Fc gamma R+ T cells to form IgE-suppressive factors. Cell sources of "inducers" are W 3/25+ Fc gamma R- T cells, cells different from the source of IgE-binding factors. The glycosylation-enhancing factor is derived from W 3/25+ F gamma R+ T cells in KLH-alum-primed spleen; the glycosylation-inhibiting factor is derived from OX 8+ T cells in KLH-CFA-primed spleen. Evidence was obtained that these lymphokines, which modulate the protein glycosylation of IgE-binding factors during their biosynthesis, are derived from antigen-primed T cells and determine the nature of IgE-binding factors formed.

Animals↗
PubMed1980

[Genetic control of plasmid F' formation. II. Role of recipient recA- in the process of plasmid F' formation].

We have chosen the process of F'-plasmid formation as a model for a study of the illegitimate, recA-independent recombination. Our genetic data showed that F'-formation was under genetic control of the Hfr donor cells. To determine the role of recipient cells in the process of F-prime formation we compared the pattern of transconjugant formation in the crosses of Hfr and F' donors with the recA-nalA+ and recA-nalA- recipients, nalA- mutation in the recipient lead to the sharp decrease of the total yield of transconjugants selected for proximal markers and decrease the fraction of conjugative plasmids in progeny. The plasmids inherited in the nalA- recipient in HfrxF- crosses possess only proximal selected markers while the appropriate distribution of proximal and more distal markers took place in the nalA+ recipient. The homogeneity for the sensitivity of nalA- progeny to the male specific phages in comparison with the nalA+ transconjugants was also observed. The data obtained show that the nalA- mutation has a strong influence on the process of final inheritance and probably formation of F'-plasmids in the recipient cells. The extent of the influence of the nalA- mutation on the pattern of F'-plasmid inheritance was dependent upon the primary F' structure formed (or existed) in the donor cell.

Conjugation, Genetic↗
PubMedDate not supplied

[Effect of the length of molecular chain on the formation of triple-helical collagen-like complex in solutions. The role of water in the formation of triple helix].

Effect of molecular chain length on the formation of the collagen-like triple helix in synthetic oligotripeptides Z-(Gly-Pro-Pro)n-OMe (n-1,2,3,...,8) in solutions has been studied, using IR- and CD-spectroscopy methods. The helix formation under different conditions is investigated: in the presence of a relatively inert solvent (chloroform), in the presence of a hydrogen bond acceptor (dioxan), in the presence of a hydrogen bond acceptor and donor as well (ethanol). Special attention is paid to the role of water in the formation of a stable triple-helical structure. Successive stages in the formation of a stable triple-helical structure in solutions during elongation of the peptide chain is revealed, which may be correlated with the helix nucleation process. A minimum peptide length, when peptide chains are still able to associate in the collagen-like triple-helical complex, involves three triplets for oligomers in chloroform solution, four triplets for oligomers in dioxan and ethanol solutions, six triplets for oligomers in aqueous solution. The main features of the completed triple-helical structure in water are found already in the oligotripeptide with n-8, where the formation one full turn of the superhelix is finished.

Circular Dichroism↗
PubMed1998

Fibrin-rich and platelet-rich thrombus formation on neointima: recombinant tissue factor pathway inhibitor prevents fibrin formation and neointimal development following repeated balloon injury of rabbit aorta.

Thrombus formation and neointimal growth are the critical events in restenosis after balloon angioplasty. However, the responses of diseased vessels to injuries caused by balloon angioplasty have not been well examined. We investigated the thrombus formation and neointimal development following the balloon injury to the previously induced neointima in the rabbit aorta and the effects of recombinant tissue factor pathway inhibitor (rTFPI) on these responses. Rabbit thoracic aortas were subjected to injury with a Fogarty 4F balloon catheter at 1.75 atm (first injury), and 4 weeks later the same vessels were subjected to the second injury with a Swan-Ganz 5F balloon catheter at 1.4 atm (mild-injury group) or 1.8 atm (severe-injury group), and immediately after that a retrograde bolus injection of rTFPI (100 microg/kg body weight) or saline was performed into the injured segments via the central tube of the Swan-Ganz catheter. Twenty minutes after the second injury, the injured surfaces were covered with platelet-rich thrombi in the mild-injury group and with fibrin-rich thrombi in the severe-injury group. Damaged intimal smooth muscle cells, which were immunohistochemically positive for tissue factor (TF), were observed beneath the fibrin-rich thrombi. The neointima 4 weeks after the second injury was significantly thicker in the severe-injury group than in the mild-injury group. The bolus infusion of rTFPI markedly inhibited fibrin formation on the injured surfaces, and significantly reduced the neointimal development in the severe-injury group at 4 weeks after the second injury. These results indicate that TF-dependent coagulation pathway is primarily responsible for fibrin-rich thrombus formation and may play an important role in neointimal development following the balloon injury to the rabbit aortic neointima. Additionally the bolus administration of rTFPI to the injured vessels could prevent mural thrombus formation and neointimal growth after balloon angioplasty.

Animals↗
PubMed1963

Antibody formation. IV. Formation of rapidly and slowly sedimenting antibodies and immunological memory to bacteriophage phi-X 174.

Injection of a sufficient dose of bacteriophage phiX 174 into guinea pigs results in the formation of rapidly sedimenting antibody molecules (19S), and later, slowly sedimenting molecules (7S). Above a threshold dose of antigen, the relative rate of 19S formation is maximal and dose-independent; below this dose, slower relative rates are obtained. The time for doubling the serum 19S level is as short as 6 to 8 hours, suggesting that the absolute rate of antibody formation per cell is increasing in addition to proliferation of antibody-producing cells. Synthesis of 19S after injection of 10(10) phiX virtually ceases at 10 days after which 19S antibody activity disappears from the circulation with a half-life of approximately 24 hours. A second injection of phiX on day 5 or 9 prolongs 19S synthesis, indicating that antigen not only can regulate the relative rate, but also is essential for continued synthesis of 19S. 19S synthesis is also prolonged in guinea pigs by injection of phiX with endotoxin or by 400 r whole body x-irradiation 24 hours after injection of phage into rabbits. The primary 7S response is not detected until approximately 1 week after immunization and relative rates are antigen-dependent. Primary 7S synthesis can continue for many months and leads to preparation for a secondary antibody response (immunological memory) during which only 7S is detected. In contrast, in animals that form precipitating 19S without detectable 7S, a second injection of phage 1 month later results in a second 19S response which closely resembles the first. These findings have led to the suggestion that formation of 19S does not lead to persisting immunological memory.

Animals↗
PubMed1978

Role of the chlC gene in formation of the formate-nitrate reductase pathway in Escherichia coli.

Five temperature-sensitive chlC mutants were isolated from Escherichia coli by the technique of localized mutagenesis. All of the mutants produced severely reduced levels of both nitrate reductase and formate dehydrogenase when grown at 43 degrees C. In three of the mutants, the nitrate reductase activity produced at the permissive temperature was shown to be thermolabile compared with the activity produced by the parent wild-type strain, both in membrane preparations and in preparations released from the membrane by deoxycholate. In each case, formate dehydrogenase activity was similar to the wild-type activity in its stability to heat. It is concluded that the chlC gene codes for at least one of the polypeptide chains of nitrate reductase and that the chlC mutations affect indirectly the formation of formate dehydrogenase.

Aldehyde Oxidoreductases↗
PubMed1983

Evidence for formation of superoxide and formate radicals in Methanobacterium formicicum.

Using spin labeling and spin trapping techniques in combination with electron paramagnetic resonance spectrometry, we have detected the formation of superoxide by whole cells of Methanobacterium formicicum under aerobic conditions in the presence and absence of sodium formate. Rates of superoxide generation have been estimated. The formation of additional free radical species, including formate, was observed. Production of these and other free radicals resulted in lipid peroxidation and concomitant cell damage.

Electron Spin Resonance Spectroscopy↗
PubMed1990

Escherichia coli formate-hydrogen lyase. Purification and properties of the selenium-dependent formate dehydrogenase component.

The formate-hydrogen lyase complex of Escherichia coli decomposes formic acid to hydrogen and carbon dioxide under anaerobic conditions in the absence of exogenous electron acceptors. The complex consists of two separable enzymatic activities: a formate dehydrogenase and a hydrogenase. The formate dehydrogenase component (FDHH) of the formate-hydrogen lyase complex was purified to near homogeneity in two column chromatographic steps. The purified enzyme was composed of a single polypeptide of molecular weight 80,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Metal analysis showed each mole of enzyme contained 3.3 g atoms of iron. Denaturation of FDHH released a compound which, when oxidized, displayed a fluorescence spectrum similar to that of the molybdopterin cofactor found in certain other enzymes. The enzyme contained selenium in the form of selenocysteine as determined by radioactive labeling of the enzyme with 75Se and amino acid analysis. FDHH activity was maximal between pH 7.5 and 8.5; however, the enzyme was maximally stable at pH 5.3-6.4 and highly unstable above pH 7.5. Nitrate and nitrite salts caused a drastic reduction in activity. Although azide inhibited FDHH activity, it also protected the enzyme from inactivation by oxygen.

Amino Acid Sequence↗
PubMed1980

Reconstitution of a formate-NADP+ oxidoreductase from formate dehydrogenase and a 5-deazaflavin-linked NADP+ reductase isolated from Methanococcus vannielii.

The formate-dependent reduction of NADP+ by extracts of Methanococcus vannielii is catalyzed by a coupled system consisting of formate dehydrogenase, a 5-deazaflavin cofactor, and 5-deazaflavin-dependent NADP+ reductase. All three components were purified from crude extracts of M. vannielii. Recombination of these components reconstituted the formate-NADP+ oxidoreductase system. The formate dehydrogenase also can utilize FAD, FMN, and a number of artificial dyes as electron acceptors, but these do not replace the 5-deazaflavin cofactor in the coupled enzyme system. The reduced form of 5-deazaflavin binds readily to the NADP+ reductase apoprotein and is not dissociated by ammonium sulfate treatment at neutral pH under anaerobic conditions. This electron transfer cofactor from M. vannielii is identical in many of its properties to the 5-deazaflavin isolated from other methane-producing bacteria.

Aldehyde Oxidoreductases↗
PubMed1997

Lumen formation during angiogenesis in vitro involves phagocytic activity, formation and secretion of vacuoles, cell death, and capillary tube remodelling by different populations of endothelial cells.

BACKGROUND: We have utilised an in vitro model of angiogenesis to investigate the morphological changes which occur during the formation of a lumen in capillary tubes. METHODS AND RESULTS: On collagen 1 gel in the presence of phorbol myristate acetate (PMA) and anti-alpha 2 beta 1 antibody, cell aggregation and alignment takes place within two hours of plating. The initial apparently homogeneous population of endothelial cells (EC) actually display at least three distinct phenotypes. One population, characterised by a phagocytic phenotype, migrated through the gel creating channels and defines the extent of the capillary network. These are later enveloped by a second population of cells characterised by intracellular vacuoles. The ultimate fate of these vacuoles is fusion with the plasma membrane. By 12 hours the original phagocytic cell population undergoes cell death, which morphologically appears apoptotic in nature. A consequence of the secretion of vacuoles and programmed cell death is the extensive remodelling of the capillary tubes, resulting in expansion of the intercellular space into a lumen. The remodelling results in 45% of the EC membrane contacting the lumenal surface at the expense of EC-EC and EC-matrix contact. A third population of cells implant between the EC involved in lumen formation and thus expand the size of the capillary tube. CONCLUSION: Thus, in the formation of a mature multicellular lumen we have identified a number of key events. First, cell-cell contact is essential in order to define the intercellular space. Second, at least three morphologically distinct subpopulations of ECs are involved. Third, vacuole formation and programmed cell death are required for expansion of the intercellular space which ultimately becomes the lumen.

Antibodies↗
PubMed2002

Anteroposterior axis formation in Xenopus limb bud recombinants: a model of pattern formation during limb regeneration.

We previously showed that recombinant limb buds with dissociated and reaggregated mesenchyme develop more than 30 digits in Xenopus laevis, which exhibits different capacities for limb regeneration at different developmental stages (Yokoyama et al. [1998] Dev Biol 196:1-10). Cell-cell contact among anterior- and posterior-derived mesenchymal cells is required for anteroposterior (AP) axis formation of recombinant limbs in an intercalary manner. However, whether one-way induction from posterior cells to anterior cells as proposed by the polarizing zone model or interactions between anterior and posterior cells evoke the AP axis formation in recombinant limbs remains unclear. In this study, we found, by a combination of X-ray irradiation and a recombinant limb technique, that not one-way induction but interactions between anterior and posterior cells accompanied by cell contribution are indispensable for AP axis formation in recombinant limbs. Shh was expressed in posterior-derived not anterior-derived cells. We propose that the recombinant limb is an excellent model for examining the axis formation mechanism in regenerating limbs because, as in recombinant limbs, cell-cell contact among cells derived from different positions of an amputation plane occurs in the blastema of regenerating limbs.

Animals↗
PubMed2000

Abnormal down-regulation of PKC is responsible for giant granule formation in fibroblasts from CHS (beige) mice--a thiol proteinase inhibitor, E-64-d, prevents giant granule formation in beige fibroblasts.

We have previously reported that the abnormally rapid down-regulation of protein kinase C (PKC) activity is responsible for the cellular dysfunction in natural killer (NK) cells and polymorphonuclear leukocytes (PMNs) from Chediak-Higashi syndrome (beige) mice. In this report, we examined whether the down-regulation of PKC is associated with giant granule formation in fibroblasts from beige mice. In cultured beige fibroblasts, the membrane-bound PKC activity declined significantly after phorbol ester stimulation. We found that E-64-d, which is a thiol proteinase inhibitor and protects PKC from calpain-mediated proteolysis, reversed the declined PKC activity and prevented giant granule formation in beige fibroblasts. Moreover, E-64-d corrected the reduced lysosomal elastase and cathepsin G activity in beige fibroblasts. In contrast, specific PKC inhibitors, chelerythrin and calphostin C, promoted giant granule formation in normal fibroblasts. We also demonstrate that ceramide production is enhanced in beige fibroblasts and is involved in the rapid down-regulation of PKC. These results suggest that the accelerated breakdown of PKC observed in beige fibroblasts is caused by enhanced ceramide production and is also responsible for giant granule formation.

Animals↗
PubMed1996

An alpha 2 beta 1 integrin-dependent pinocytic mechanism involving intracellular vacuole formation and coalescence regulates capillary lumen and tube formation in three-dimensional collagen matrix.

Human endothelial cells, when suspended within three-dimensional collagen matrices, develop intracellular vacuoles that coalesce to form capillary lumens and tubes. Vacuole and lumen formation are completely dependent on the collagen-binding integrin alpha 2 beta 1, while other endothelial cell integrins had no apparent influence. Vacuole formation occurs by a pinocytic process with internalization of plasma membrane and molecules from the extracellular space, such as fluorescent tracers. By immunofluorescence, vacuole membranes were found to contain associated cell surface proteins, proteins involved in endosomal trafficking (i.e., caveolin and annexin II), and F-actin. Furthermore, some vacuole compartments contained von Willebrand factor. Integrin-regulated vacuole formation and coalescence are major mechanisms controlling capillary lumen and tube formation within a three-dimensional extracellular matrix.

Capillaries↗
PubMed1991

Molecular mechanisms of deletion formation in Escherichia coli plasmids. I. Deletion formation mediated by long direct repeats.

Derivatives of plasmid pBR327 with the tet gene interrupted by 165 pb or 401 bp direct repeats were constructed. In cells harboring these plasmids, deletions which restored the wild-type tet gene gave rise to tetracycline-resistant colonies, thereby allowing a simple phenotypic test for deletion formation. The frequencies of deletions in these plasmids were measured in Escherichia coli strains proficient or deficient in general recombination. The structure of plasmid DNA isolated from tetracycline-resistant transformants was analyzed by agarose gel electrophoresis, restriction mapping and sequencing. The data presented here demonstrate that deletion formation is always associated with dimerization of plasmid DNA. Dimeric plasmids were of two types. Those which carried both a deletion and a compensating duplication were the major type in a Rec+ background and were rare in recA, recF, recJ and recO backgrounds. Dimers of the second type contained deletions, but no compensating duplications, and their formation was RecA-independent. The data presented demonstrate that deletion formation mediated by long direct repeats is mainly the result of unequal crossing-over between two plasmid molecules.

Chromosome Mapping↗
PubMed2001

The level of pyruvate-formate lyase controls the shift from homolactic to mixed-acid product formation in Lactococcus lactis.

Regulation of pyruvate-formate lyase (PFL) activity in vivo plays a central role in the shift from homolactic to mixed-acid product formation observed during the growth of Lactococcus lactis on glucose and galactose, respectively. Characterisation of L. lactis MG1363 in anaerobic batch cultures showed that the specific in vivo activity (flux) of PFL was 4-fold higher in L. lactis cells grown with galactose, compared with cells grown with glucose. The change in the PFL flux correlated with the observed variation in the PFL enzyme level, i.e. the PFL enzyme level was 3.4-fold higher in L. lactis cells grown on galactose than in those grown on glucose. To investigate whether a variation in the level of PFL was responsible for the shift in pyruvate metabolism, L. lactis strains with altered expression of pfl were constructed. The pfl gene was expressed under the control of different constitutive promoters in L. lactis MG1363 and in the PFL-deficient strain CRM40. Strains with five different PFL levels were obtained. Variation in the PFL level markedly affected the resulting end-product formation in these strains. During growth on galactose, the flux towards mixed-acid products was to a great extent controlled by the PFL level. This demonstrates that a regulated PFL level plays a predominant role in the regulation of the metabolic shift from homolactic to mixed-acid product formation in L. lactis.

Acetyltransferases↗
PubMed1994

PAF stimulates cAMP formation in P388D1 macrophage-like cells via the formation and secretion of prostaglandin E2 in an autocrine fashion.

The role of cAMP in the formation of prostaglandin E2 (PGE2) was investigated in bacterial lipopolysaccharide (LPS)-primed P388D1 macrophage-like cells stimulated with platelet activating factor (PAF). cAMP levels and PGE2 secretion were correlated with stimulation by PAF or ionomycin. Indomethacin inhibited cAMP formation induced by PAF, but not PGE2-stimulated cAMP production. Inositol (1,4,5)-trisphosphate levels were strongly reduced by exogenous PGE2 and increased by H-89, an inhibitor of PKA. However, exogenous PGE2 did not affect PAF-stimulated PGE2 formation. These results suggest that cAMP levels in P388D1 cells are regulated by PGE2 in an autocrine fashion. Evidence is presented that this feedback mechanism regulates inositol (1,4,5)-triphosphate levels in these cells, while PGE2 formation is not affected.

Animals↗
PubMed2003

Role of vascular endothelial growth factor and placental growth factor in basal adhesion formation and in carbon dioxide pneumoperitoneum-enhanced adhesion formation after laparoscopic surgery in transgenic mice.

OBJECTIVE: To evaluate the role of vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) in adhesion formation after laparoscopic surgery. DESIGN: Prospective, randomized study. SETTING: Academic research center. ANIMAL(S): Female wild-type mice and transgenic mice (n = 110), expressing exclusively VEGF-A(164) (VEGF-A(164/164)) or deficient for VEGF-B (VEGF-B(-/-)) or for PlGF (PlGF(-/-)). INTERVENTION(S): Adhesions were induced during laparoscopy. To evaluate "basal adhesions" and "CO(2) pneumoperitoneum-enhanced adhesions," the pneumoperitoneum was maintained for a minimum (10 minutes) or prolonged (60 minutes) period. The role of PlGF was also evaluated by administration of antibodies. MAIN OUTCOME MEASURE(S): Adhesions were blindly scored after 7 days. RESULT(S): In all wild-type mice, CO(2) pneumoperitoneum enhanced adhesion formation. In comparison with wild-type mice, basal adhesions were higher in VEGF-A(164/164) mice and similar in VEGF-B(-/-) and PlGF(-/-) mice. Pneumoperitoneum did not enhance adhesions in any of these transgenic mice. The effects observed in PlGF(-/-) mice were confirmed in PlGF antibody-treated mice. CONCLUSION(S): The data demonstrate that the VEGF family plays a role in adhesion formation and confirm that CO(2) pneumoperitoneum enhances adhesions. VEGF-A(164) has a direct role in basal adhesions. Absence of pneumoperitoneum-enhanced adhesions in VEGF-A(164/164), VEGF-B(-/-), and PlGF(-/-) mice indicates up-regulation of VEGF-A(164), VEGF-B, and PlGF by CO(2) pneumoperitoneum as a mechanism for pneumoperitoneum-enhanced adhesion formation.

Animals↗
PubMed2003

Role of hypoxia inducible factors 1alpha and 2alpha in basal adhesion formation and in carbon dioxide pneumoperitoneum-enhanced adhesion formation after laparoscopic surgery in transgenic mice.

OBJECTIVE: To evaluate the role of hypoxia inducible factors (HIFs) 1alpha and 2alpha in adhesion formation after laparoscopic surgery. DESIGN: Prospective, randomized study. SETTING: Academic research center. ANIMAL(S): Forty Swiss/129SvJ wild-type mice and transgenic mice partially deficient for the genes encoding for HIF-1alpha (HIF-1alpha(+/-)) or HIF-2alpha (HIF-2alpha(+/-)). INTERVENTION(S): Adhesions were induced by standardized lesions during laparoscopy. To evaluate "basal adhesions" and "pneumoperitoneum-enhanced adhesions," the pneumoperitoneum was maintained for a minimum (10 minutes) or prolonged (60 minutes) period, respectively. MAIN OUTCOME MEASURE(S): Adhesions were blindly scored after 7 days. RESULT(S): In both HIF-1alpha and HIF-2alpha wild-type mice, pneumoperitoneum enhanced adhesion formation. In comparison with wild-type mice, basal adhesions were lower in HIF-1alpha(+/-) and similar in HIF-2alpha(+/-) mice. Pneumoperitoneum did not enhance adhesion formation in HIF-1alpha(+/-) or in HIF-2alpha(+/-) mice. Therefore, in comparison with the correspondent wild-type mice, pneumoperitoneum-enhanced adhesions were lower in HIF-1alpha(+/-) and HIF-2alpha(+/-) mice. CONCLUSION(S): These data confirm that CO(2) pneumoperitoneum enhances adhesion formation and indicate that this effect is mediated, at least in part, by an up-regulation of HIF-1alpha and HIF-2alpha.

Animals↗