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At least 1,117 records · Page 62Linked to original sources
PubMed1999

Suppressive influences of methotrexate on the generation of CD14(+) monocyte-lineage cells from bone marrow of patients with rheumatoid arthritis.

An adequate supply of peripheral blood monocytes, granulocytes, and platelets is necessary for an optimal inflammatory process. We have previously demonstrated that the generation of CD14(+) monocyte lineage cells from the bone marrow is accelerated in patients with rheumatoid arthritis (RA). The current studies examined the influences of methotrexate (MTX), a potent disease modifying antirheumatic drug (DMARD), on the capacity of bone marrow progenitor cells to generate CD14(+) cells in patients with RA, in order to delineate its mechanism of action. CD14(-) cells purified from bone marrow specimens of 14 patients with active RA were cultured in the presence or the absence of pharmacologically attainable concentrations of MTX (0.2 microM). After incubation for 14 days, the cells were analyzed by flow cytometry for expression of CD14 and HLA-DR. The generation of CD14(+) cells from RA bone marrow CD14(-) progenitor cells was significantly suppressed by MTX. However, the expression of HLA-DR on bone marrow-derived CD14(+) cells was not significantly influenced by MTX. There was no significant difference in the effect of MTX on the generation of CD14(+) cells between patients with prednisolone and those without prednisolone. The production of IL-12 in bone marrow cell cultures was not inhibited, but was rather enhanced, by MTX, suggesting that the suppression of the generation of CD14(+) cells might not be due to the inhibition of cytokine production. The results are consistent with the hypothesis that one of the effects of DMARDs may involve the interference with monocyte differentiation in the bone marrow. Moreover, the data suggest that the generation of CD14(+) cells and the expression of HLA-DR on such marrow-derived CD14(+) cells are regulated by different mechanisms.

Adult↗
PubMed2002

Comparison of the functional properties of murine dendritic cells generated in vivo with Flt3 ligand, GM-CSF and Flt3 ligand plus GM-SCF.

Flt3 ligand (FL) and granulocyte-macrophage colony-stimulating factor (GM-CSF) are important growth factors for dendritic cells (DC). Substantial numbers of DC can be generated in vivo following the administration of either factor. We sought to extend our knowledge of the functional properties of these cells including their ability to prime naïve CD8(+) T cells. In addition, we compared the nature of the DC generated in vivo with the single cytokines to those generated with the combination of FL+polyethylene glycol-modified GM-CSF (pGM-CSF). Treatment with FL+pGM-CSF yielded greater numbers of both CD11b(low) and CD11b(high) DC than with either cytokine alone, and these DC were more efficient at antigen (Ag) capture. The FL+pGM-CSF-generated CD11b(low) DC lacked expression of CD8alpha. Following treatment with LPS in vivo, all DC subsets upregulated CD40, CD80, CD86, and MHC class II expression, but surprisingly Ag capture was not downregulated and some DC subsets retained expression of intracellular MHC class II vesicles. Thus, even after activation in vivo with LPS, DC retained Ag capture properties of immature DC, and Ag presentation/costimulation properties of mature DC. Though all DC subsets stimulated CD4(+) T cell proliferation equivalently, FL-generated DC were more efficient at priming Ag-specific CD8(+) cytolytic T cells than DC generated with either pGM-CSF alone or FL+pGM-CSF, and CD11b(high) DC were more efficient at priming CD8(+) T cells than CD11b(low) DC.

Adjuvants, Immunologic↗
PubMed1999

Spontaneous generation of superoxide anion by human lens proteins and by calf lens proteins ascorbylated in vitro.

The proteins isolated from aged human lenses and brunescent cataracts exhibit extensive disulfide bond formation. Diabetic rat lenses similarly contain disulfide-bonded protein aggregates. These observations are consistent with the known link between diabetes, glycation and oxidative damage, and suggest a role for reactive oxygen species (ROS) in this process. To assess whether the glycation-related modifications in human lens proteins spontaneously generate ROS, superoxide anion formation was measured using both cataractous lens proteins and calf lens proteins glycated in vitro with ascorbic acid (ascorbylated). The water-insoluble fraction from aged normal human lenses generated 0.3-0.6 nmol superoxide h(-1)mg protein(-1), whereas the activity increased to 0.5-1.8 nmol h(-1)mg protein(-1)with the WI fraction from brunescent cataracts, and 2.3 nmol h(-1)mg protein(-1)with calf lens proteins ascorbylated for 4 weeks in vitro. The activity in the human lens proteins was observed in both the water-soluble and water-insoluble fractions, and was completely dependent upon the presence of oxygen. The pH optimum curve for superoxide formation increased from pH 6.5 to 10 with both the cataract and ascorbylated proteins. The superoxide-generating activity in human lens was completely bound to a boronate affinity column, but only partially bound with the ascorbylated proteins. The superoxide anion produced by a 5 m m solution of purified N(epsilon)-fructosyl-lysine was barely detectable, and therefore, could not account for the superoxide formed by any of the lens protein preparations. Also, superoxide formation increased 10-fold at pH 8.8 with fructosyl-lysine, but only 1.3-1.8-fold with human lens proteins. The addition of copper-stimulated superoxide formation with glycated bovine serum albumin, but no stimulation was seen with cataractous proteins. Assays of specific compounds showed that catechol, hydroquinone, 3-OH kynurenine and 3-OH anthranylic acid exhibited the greatest activity for superoxide generation, but had a very short halflife. 2,3-Dihydroxypyridine and 4,5 dihydroxynaphthalene were one and two orders of magnitude less reactive. In long-term incubations at 37 degrees, cataractous proteins retained the potential to produce superoxide anion, losing only half of the initial activity after 6-7 days. Therefore, the water-insoluble fraction from aged human lenses and dark brown cataracts are potentially capable of generating >100 nmol mg protein(-1)and >170 nmol mg protein(-1)of superoxide anion respectively, likely due to the presence of advanced glycation endproducts in human lens proteins. This spontaneous generation of superoxide anion in vivo could account for a major portion of the oxidation of sulfur amino acids seen during aging and cataract formation.

Aged↗
PubMed1995

A two-generation reproduction study in rats receiving drinking water containing vinyl acetate.

Vinyl acetate (VA) is a commonly used chemical in polymerization and copolymerization processes and as a chemical intermediate. As part of a collaborative effort between VA producers of the United States and British Petroleum, the present study was carried out to provide a base set of data for risk assessment. Groups of male and female Crl:CD(SD)BR rats were given 0, 200, 1000, or 5000 ppm VA via the drinking water over two generations. In addition, a cross-mating trial of control and 5000-ppm male and female rats was conducted in the F1 generation to investigate the slightly decreased litter production in the high-dose group. No treatment-related mortality was observed in any of the groups. Water consumption was significantly reduced in the 5000-ppm groups in both generations and in the 1000-ppm F1 female rats. The body weights of the F0 and F1 male rats and the F1 female rats in the 5000-ppm group tended to be slightly lower than those of the control group. Body weight gain was significantly decreased during lactation in the F0 females at 5000 ppm and in the F1 females at 1000 and 5000 ppm. Pup weights in the F1 generation, but not in the F2 generation, were significantly lower than those of the control on lactation Day 21. The number of litters produced in the F1 generation in the 5000-ppm group was slightly lower than that of the control group and was attributed to lower fertility. Fewer pups were produced when control females were mated with the 5000-ppm males; however, the decrease was due to poor mating performance rather than decreased fertility. No decrease was apparent when the 5000-ppm females were mated with the control group males. Under the conditions of this study, the no-observed adverse effort level was considered to be 1000 ppm.

Administration, Oral↗
PubMed2002

Prorenin uptake in the heart: a prerequisite for local angiotensin generation?

Interference with locally generated angiotensin II most likely underlies the beneficial effects of renin-angiotensin system blockers in cardiac disorders. Since renin is not synthesized in the heart, this enzyme must be sequestered from the circulation in order to allow angiotensin generation at cardiac tissue sites. This review addresses the various ways through which circulating (i.e., kidney-derived) renin may reach cardiac tissue sites, considering in particular the possibility that prorenin, the inactive precursor of renin, is involved in cardiac angiotensin generation, as the plasma concentrations of prorenin are tenfold higher than those of renin. Renin and prorenin diffuse into the cardiac interstitial space and bind to cardiac (pro)renin receptors/renin-binding proteins. One of these receptors is the mannose 6-phosphate/insulin-like growth factor II receptor. This receptor not only binds mannose 6-phosphate-containing ligands like renin and prorenin, it also internalizes these enzymes, and activates prorenin intracellularly. This process possibly represents (pro)renin clearance, since intracellular angiotensin generation could not be demonstrated following (pro)renin uptake by cardiomyocytes. Angiotensin II-mediated myocyte proliferation did occur when incubating cardiomyocytes with prorenin plus angiotensionogen. The effects of prorenin plus angiotensinogen were comparable to those of 100nmol/l angiotensin II, although the angiotensin II levels in the medium during exposure of the cells to prorenin plus angiotensinogen were <1nmol/l. This suggests that cardiac angiotensin II generation by circulating renin occurs predominantly on the cell surface. The presence of ACE and/or renin on the cell membrane, in the microenvironment of angiotensin receptors, would allow maximal efficiency of local angiotensin II generation, i.e., immediate binding of angiotensin II to its receptors with minimal loss into the extracellular space.

Angiotensins↗
PubMed1997

Beta-adrenergic stimulation down-regulates neutrophil priming for superoxide generation, but not elastase release.

Platelet-activating factor (PAF) concordantly primes neutrophils (PMNs) for superoxide generation and elastase release. beta-Adrenergic stimulation of PMNs enhances cAMP-dependent protein kinase A (PKA) activity and has been shown to inhibit PAF-mediated NADPH-oxidase activity. PMN superoxide generation is thought to play a predominate microbicidal role, whereas elastase is known to mediate untoward PMN-endothelial interactions. We hypothesized that beta-adrenergic neutrophil stimulation has disparate effects on PAF-mediated PMN superoxide generation versus elastase release. Human PMNs were isolated using a standard Ficoll/Hypaque gradient. PMNs were then primed with PAF (200 nM) and activated with fMLP (1 microM). Subsets of PMNs were pretreated for 5 min with a beta agonist (10(-4) M isoprotereno) or an adenylate cyclase agonist (10(-5) M forskolin). Superoxide generation was determined by superoxide dismutase inhibitive cytochrome c reduction. Elastase activity was measured by the cleavage of n-methoxylsuccinyl-A-A-P-V-p-nitroanilide. Pretreatment with isoproterenol and forskolin yielded superoxide generation of 3.2 +/- 0.6 and 3.1 +/- 1.2 nmole/2.5 x 10(5) PMN/min compared to 9.0 +/- 0.6 nmole/2.5 x 10(5) PMN/min for PAF/fMLP alone, whereas isoproterenol and forskolin did not significantly affect PAF-mediated neutrophil elastase release, 22.4 +/- 5.3 and 24.0 +/- 3.6%, respectively, compared to 39.4 +/- 9.1% for PAF/fMLP alone. Disparate PMN signal transduction for superoxide generation versus elastase release may explain the SICU clinical paradox, in which patients are both susceptible to infection and vulnerable to PMN-mediated multiple organ failure.

Adrenergic beta-Agonists↗
PubMed2001

Nitric oxide- and oxygen-derived free radical generation from control and lipopolysaccharide-treated rat polymorphonuclear leukocyte.

Previous studies from this lab have shown NO-mediated modulation of free radical generation from polymorphonuclear leukocytes (PMNs), following hypoxic-reoxygenation as well as in the normoxic cells. The present study is an attempt to investigate further the regulation of NO and free radical generation in the lipopolysaccharide (LPS)-treated PMNs. PMNs were isolated from the rat blood and peritoneal cavity, 4 h after LPS (1 mg/kg, i.p.) treatment. Nitric oxide synthase (NOS) activity and nitrite content were increased in the peripheral and peritoneal PMNs following LPS treatment. An increase in the apparent V(max) for l-arginine uptake was also observed in the LPS-treated peripheral PMNs, while peritoneal PMNs exhibited increase in both apparent V(max) and affinity for l-arginine. Synthesis of nitrite did not augment after increasing the availability of substrate to control PMNs, however, peripheral and peritoneal PMNs from LPS-treated rats utilized l-arginine more efficiently for nitrite synthesis. NOS activity, l-arginine uptake, and its utilization were maximal in the peritoneal PMNs. Arachidonic acid (AA, 1 x 10(-6) M)-induced free radical generation from PMNs was also enhanced significantly after LPS treatment. Preincubation of PMNs with nitrite elevated the free radical generation and myeloperoxidase (MPO) release. MPO and antioxidant enzyme activity in the PMNs was significantly augmented after LPS treatment. NOS inhibitors, aminoguanidine and 7-nitroindazole, inhibited arachidonic acid-induced free radical generation from LPS treated PMNs. The results obtained thus indicate that augmentation of free radical generation from rat PMNs following LPS treatment appears to be regulated by NO and MPO.

Animals↗
PubMed1997

Bisaramil and antiarrhythmics as inhibitors of free radical generation.

The aim of this study was to investigate the effect of bisaramil--an antiarrhythmic drug under clinical trials-on free radical generation of isolated polymorph neutrophil granulocytes (PMN) and furthermore to compare its activity to that of well-known antiarrhythmics which have different modes of action. PMNs were isolated from healthy beagle dogs, and superoxide radical generation was induced by phorbol-myristate-acetate. Stimulated free radical generation capacity of PMNs and the time lag necessary for the initiation of free radical production were measured. All compounds were used at the concentrations of 10, 25, 50, 75, 100 micrograms ml-1. None of the antiarrhythmics stimulated by itself the free radical generation. Bisaramil exerted concentration dependent inhibitory effect on PMA-stimulated free radical generation and prolonged the time lag concentration dependently. At the investigated concentration range of antiarrhythmics only propafenon, mexiletine and diltiazem showed similar activity to bisaramil, but clear concentration dependency could not be seen in any of the cases. According to the results of this study inhibition of the stimulated free radical production of isolated PMNs cannot be closely connected merely to either membrane stabilizing or Ca-antagonistic activity of drugs. In vitro and earlier measured in vivo inhibitory action of bisaramil on free radical generation indicate a possible cardioprotective effect existing independently from its antiarrhythmic one. This observation may be important in outlining of the clinical indication field of bisaramil, and may be useful in the treatment of reperfusional damage.

Animals↗
PubMed1999

Two-generation reproductive toxicity study of plant stanol esters in rats.

Plant stanol esters are intended for use as an ingredient in food to reduce the absorption of cholesterol from the gastrointestinal tract. Consumption of plant stanol esters has a demonstrated diet-derived public health benefit, as shown by numerous clinical studies. Plant stanol esters are ring-saturated analogs of common dietary sterols that are transesterified with fatty acids from vegetable oils such as canola oil. The reproductive and developmental toxicity of plant stanol esters was investigated in male and female Wistar rats during F0 and F1 generations using dietary concentrations of 1.75, 4.38, and 8.76% stanol esters (equivalent to 1, 2.5, and 5% total stanols). No adverse treatment-related effects were noted on reproductive performance of male or female rats in any dose group. Increased food consumption was observed in high-dose F0 generation males throughout the entire premating period and in F1 males at specific time periods during the premating period. This increase in food consumption was also observed in F0 generation females (mid- and high-dose groups) and F1 generation females (low-, mid-, and high-dose groups) at specific time periods throughout the 10-week premating period. At different intervals throughout the gestation and lactation periods, increased food consumption was observed in F0 generation females of the mid- and high-dose groups, while increased food consumption was noted in F1 generation females of the mid- and high-dose groups during gestation, but not during lactation. Such increases in food consumption are expected as a result of the animals' attempt to compensate for the reduced caloric value of the test diet compared to controls. No adverse developmental effects were noted in F1 or F2 pups of the low- and mid-dose groups based on evaluation of the following parameters: litter size, pup mortality, pups weights, and sex ratio. However, a treatment-related effect on body weight and body weight change was observed in both F1 and F2 male and female pups of the high-dose group, particularly during the latter stages of lactation (postnatal days 14 and 21) in F1 pups, and during the majority of the lactation period (postnatal days 4-21). Lower body weight in the high-dose pups is attributed to a reduction in the caloric value of the test diet compared to control. The pups, unlike adult animals, are particularly sensitive to reductions in caloric value of feed since they are in a rapid growth phase of their development. It is likely that they could not increase their food consumption enough to adequately meet their caloric and nutritional needs. In conclusion, dietary concentrations of up to 4.38% plant stanol esters (equivalent to 2.5% total stanols in the diet) are not associated with adverse effects on reproduction, pup mortality, pup body weight, or pup body weight change.

Animals↗
PubMed1993

Evidence for structural changes in crossbridges during force generation.

During muscle contraction, it is generally thought that myosin heads undergo large scale conformational changes, such as an oar-like rotation between 90 degrees and 45 degrees while attached to actin. However, evidence for conformational changes of the attached crossbridges associated with force generation has been ambiguous. In this study, we compared the conformations of attached crossbridges in (i) the pre-force generating state, (ii) force generating state, (ii) rigor state. High resolution equatorial X-ray diffraction patterns have been obtained from single chemically skinned rabbit psoas fibers under relaxed, fully Ca(2+)-activated and rigor conditions. The experimental condition was chosen (ionic strength = 50 mM and temperature = 5 degrees C) such that there are large fractions (80-100%) of crossbridges attached in all the three states, and the attached crossbridges in the relaxed muscle represent the pre-force generating state. Upon activation, changes in the two innermost intensities I10 and I11 did not follow the familiar reciprocal changes. Instead, there was almost no change in I11 while I10 decreased by 30%. Similarly, greater changes were found in I10 as the fiber goes into rigor from the activate state. Changes were also found in the higher order reflections suggesting that the structure of the force generating crossbridges is not a mixture of those found in the weakly bound and rigor crossbridges. Therefore, our data provides evidence that the average conformation of the force generating crossbridges is different from the weakly attached and from rigor crossbridges.

Actins↗
PubMed1995

A computational theory for movement pattern recognition based on optimal movement pattern generation.

We have previously proposed an optimal trajectory and control theory for continuous movements, such as reaching or cursive handwriting. According to Marr's three-level description of brain function, our theory can be summarized as follows: (1) The computational theory is the minimum torque-change model; (2) the intermediate representation of a pattern is given as a set of via-points extracted from an example pattern; and (3) algorithm and hardware are provided by FIRM, a neural network that can generate and control minimum torque-change trajectories. In this paper, we propose a computational theory for movement pattern recognition that is based on our theory for optimal movement pattern generation. The three levels of the description of brain function in the recognition theory are tightly coupled with those for pattern generation. In recognition, the generation process and the recognition process are actually two flows of information in opposite directions within a single functional unit. In our theory, if the input movement trajectory data are identical to the optimal movement pattern reconstructed from an intermediate representation of some symbol, the input data are recognized as that symbol. If an error exists between the movement trajectory data and the generated trajectory, the putative symbol is corrected, and the generation is repeated. In particular, we present concrete computational procedures for the recognition of connected cursive handwritten characters, as well as for the estimation of phonemic timing in natural speech. Our most important contribution is to demonstrate the computational realizability for the 'motor theory of movement pattern perception': the movement-pattern recognition process can be realized by actively recruiting the movement-pattern formation process. The way in which the formation process is utilized in pattern recognition in our theory suggests a duality between movement pattern formation and movement pattern perception.

Algorithms↗
PubMed1980

Fission MO-99/Tc-99m Generators -- a study of their performance and quality.

Five 99mTc-generators, based on fission Mo-99, from five different manufacturers were studied in April and May of 1977 -- with regard to their performance and to the quality of the eluates. The study covers types of generators not already dealt with in a previous publication [5]. One generator was overloaded with Mo-99; one generator had Tc-99m yields below 70%. One generator yielded eluates containing appreciable gamma-emitting impurities other than Mo-99. Two generators yielded eluates containing trace amounts of Al+++. The content of alpha- and pure beta-emitting nuclidic impurities (other than Tc-99) were in all cases below the limits set in the DLS 79 [2] monograph on Tc-99m pertechnetate obtained from fission Mo-99.

Drug Contamination↗
PubMed1994

Enrichment of generated murine osteoclasts.

Biochemical and molecular studies of osteoclasts generally require cells in a reasonable degree of purity. The chicken has been extremely useful in this regard, as abundant avian osteoclasts can be generated in vitro entirely from pure populations of marrow macrophage precursors. Propagation of murine osteoclasts is, in contrast, far less efficient, demanding the presence of stromal cells. The aims of this study were to develop a method by which murine osteoclasts generated in culture, can be effectively enriched while maintaining viability and, to explore the mechanisms by which stromal cells promote murine osteoclast generation and survival. We find that 10(6) fractionated murine marrow cells enriched, for marrow-residing colony-forming units (CFU-cs), yield 3000-4000 tartrate-resistant acid phosphatase (TRAP)-expressing multinucleated giant cells when cultured for 12 days with ST-2 stromal cells. These cells are osteoclasts as evidenced by their ability to "pit" bone slices, resorb radiolabeled bone particles, and generate cyclic AMP in response to calcitonin. Treatment of these generated osteoclast cultures with bacterial collagenase for 2 hours at 37 degrees selectively removes virtually all ST-2 cells, yielding a > 60% pure population of TRAP and calcitonin receptor-expressing cells, 90% of which are viable. These cells continue to respond to calcitonin and survive for 24 hours in the absence of ST-2 cells. We also found that murine osteoclast generation depends upon contact of osteoclast precursors with viable ST-2 cells. Furthermore, the stromal cells secrete macrophage colony-stimulating factor (CSF-1), and the anti-CSF-1 antibody 5A1 inhibits murine osteoclastogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Phosphatase↗
PubMed1993

The generation of colony-forming cells (CFC) and the expansion of hematopoiesis in cultures of human cord blood cells is dependent on the presence of stem cell factor (SCF).

We have analyzed the effect of stem cell factor (SCF), alone or in combination with other growth factors, on the generation of colony-forming cells (CFC) and on the expansion of hematopoiesis in vitro from light density, soybean agglutinin-, CD34+ cord blood cells under serum-deprived conditions. The growth factors were either added only once at the onset of the culture or added every few days when the cultures were demidepopulated and refed with fresh medium. No growth factor, alone, generated CFC or expanded hematopoiesis under these conditions. However, SCF, in combination with interleukin 3 (IL-3) or with "late-acting factors" (granulocyte colony-stimulating factor (G-CSF) or erythropoietin (Epo)), generated large numbers of mature cells as well as CFC. The number of CFC generated depended on the refeeding procedure adopted. In cultures never refed, the CFC numbers increased from < 160 CFC/culture at day 0 to > 3000 CFC at day 10. The CFC numbers stayed above the input levels for 25 days before declining. Almost no CFC were detectable after one month. In contrast, in cultures regularly refed, CFC were detectable for at least 40 days. The lineages of the mature cells and the types of CFC generated varied with the different growth factors. In the presence of SCF plus IL-3, erythroid burst-forming cells (BFU-E) and granulocyte/macrophage colony-forming cells (GM-CFC) were generated and erythroid as well as myelomonocytic precursors were present among the differentiated cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, CD↗
PubMed1985

Chemiluminescence and superoxide generation by leukocytes stimulated by polyelectrolyte-opsonized bacteria. Role of histones, polyarginine, polylysine, polyhistidine, cytochalasins, and inflammatory exudates as modulators of oxygen burst.

Human blood leukocytes generate intense luminol-dependent chemiluminescence (LDCL) following stimulation by streptococci and by Gram negative rods which had been preopsonized by cationic polyelectrolytes (histone, poly L-arginine-PARG, poly L-histidine-PHSTD). Streptococci but not Gram negative rods or hyaluronic acid-rich streptococci (group C) also induced intense LDCL following opsonization with the anionic polyelectrolytes-dextran sulfate or polyanethole sulfonate (liquoid) suggesting that the outer surfaces of different bacteria bound anionic polyelectrolytes to different extents. Both normal and immune serum, synovial fluids and pooled human saliva inhibited the LDCL responses induced by streptococci preopsonized with poly cations. On the other hand, bacteria which had been first preopsonized by the various body fluids and then subjected to a second opsonization by cationic ligands ("sandwiches"), induced a very intense LDCL response in leukocytes. Streptococci which had been preopsonized by PARG, histone or by PHSTD also triggered superoxide generation by blood leukocytes, which was markedly enhanced by a series of cytochalasins. PHSTD alone induced the formation of very large amounts of superoxide. Paradoxically, the same concentrations of cytochalasins B or C which markedly boosted the generation of superoxide following stimulation of leukocytes with soluble or particulate ligands, had a strong inhibitory effect on the generation of LDCL. On the other hand cycochalasins failed to inhibit LDCL which had been induced by phorbol myristate acetate (PMA). Peritoneal macrophages which had been harvested from C. parvum-stimulated mice, generated more LDCL and superoxide following stimulation by PARG than macrophages obtained from proteose peptone-stimulated mice. Macrophages which had been activated either by proteose peptone or by C. parvum and cultivated for 2 hours on teflon surfaces, generated much more LDCL than macrophages which had been cultivated for 24 hours on teflon surfaces. Both cationic and anionic polyelectrolytes mimic the effects of antibodies as activators of the oxygen burst in blood leukocytes and in macrophages. Such polyelectrolytes can serve as models to further study leukocyte-bacteria interactions in infectious and inflammatory sites.

Adult↗
PubMed1993

The brainstem esophagomotor network pattern generator: a rodent model.

The evidence reviewed in this essay supports the following working model of the central function generator for esophageal peristalsis in the rat: solitarial subnucleus centralis (NTSc) neurons operate in a dual capacity as esophagomotor reflex interneurons and as command neurons programming respective outputs from nucleus ambiguus compact formation (AMBc) motoneurons during secondary and primary peristalsis. In both conditions, there is a critical requirement for cholinergic input which enables NTSc neurons to generate the timed sequence of AMBc motoneuronal activity. In primary peristalsis, the cholinergic coupling mechanism is activated centrally, probably via projections from deglutitive premotor neurons to the parvicellular reticular formation and thence to the NTS. In reflex (or secondary) peristalsis, the cholinergic input could in part be generated by cholinergic vagal viscerosensory fibers innervating the esophagus. Postulated connections between NTS deglutitive neurons and the parvicellular cholinergic neurons of the intermediate reticular formation have yet to be demonstrated. Premotor input from NTSc to AMBc is generated by somatostatinergic and excitatory aminoacidergic neurons. Coactivation of both inputs by cholinergic afferents is necessary to generate esophagomotor output from AMBc neurons. The model under study is derived from investigations into central mechanisms governing striated muscle peristaltic activity. Whether the basic operational principles revealed thus far apply to peristaltic pattern generation in species with a smooth muscle esophagus, requires further investigation.

Animals↗
PubMed1995

Regulation of superoxide anion generation in bovine alveolar macrophages by bacterial lipopolysaccharide, serum proteins, and modulators of signal transduction.

The respiratory burst of phagocytes in an important leukocyte function which results in generation of oxygen species that are both microbicidal and potentially damaging to host tissues. We investigated regulation of the respiratory burst of alveolar macrophages in response to lipopolysaccharide (LPS) derived from gram-negative bacteria, serum proteins, and several modulators of signal transduction. When employed as a single stimulus, LPS (E. coli 055:B5, 10 ng/ml-1 microgram/ml) was a weak stimulus for generation of superoxide anion (O2-) as compared to the potent effect of the protein kinase C activator, phorbol 12-myristate 13-acetate (PMA; 500 ng/ml). However, when LPS was combined with fetal bovine serum (FBS; 0.4-1.0% vol/vol, equivalent to 128-320 micrograms protein/ml), O2- generation was enhanced approximately two-fold over LPS alone. A chromatographically-derived bovine serum fraction which contained bovine lipopolysaccharide-binding protein (bLBP; 0.25-1.0 microgram/ml) was an effective substitute for FBS at a much lower protein concentration than whole FBS, and a similar synergistic effect with LPS on O2- generation was observed. Stimulation of macrophages for generation of O2- either with LPS alone or with LPS plus serum/serum fraction was suppressed by the protein tyrosine kinase inhibitor heribimycin A (0.2 ng/ml), and the calcium chelator BAPTA (12 microM), but not by modulators of G-proteins, including pertussis toxin (10 ng/ml) and cholera toxin (5 micrograms/ml protein). Essentially complete inhibition of O2- synthesis by herbimycin A and BAPTA occurred in the presence of LPS and the bLBP-containing serum fraction (1 microgram/ml protein), but only partial inhibition (46.7% and 64.1%, respectively) was observed in the presence of LPS plus FBS (256 micrograms/ml protein). These results indicate that when LPS is used as a sole stimulus it induces modest respiratory burst activity. However, when LPS is combined with appropriate serum components, it stimulates alveolar macrophages to generate larger amounts of O2-. Cellular signaling pathways important in stimulation of macrophages by LPS and serum components are protein tyrosine kinase- and Ca(++)-dependent, but do not relay on G-protein-mediated signaling.

Animals↗
PubMed1987

In vitro effect of N-methoxy-3-(3,5-ditert-butyl-4-hydroxybenzylidene)-2-pyrrolidon e (E-5110), a novel nonsteroidal antiinflammatory agent, on generation of some inflammatory mediators.

Cultured rat synovial cells generate PGE2 upon stimulation with a factor derived from rate polymorphonuclear cells (Prostaglandins 27, 697, 1984). E-5110 inhibited PGE2 generation by the synovial cells. The IC50 values (microM) for inhibition of PGE2 generation were 0.026 for E-5110, 0.008 for indomethacin, 0.112 for piroxicam, 0.003 for R-830, 0.667 for BW-755C and 2.05 for benoxaprofen. Calcium ionophore A-23187-stimulated LTB4 generation by human neutrophils was inhibited by E-5110 with an IC50 value of 0.20 microM, which was similar to NDGA. The inhibition of LTB4 by E-5110 was more potent than that of R-830, BW-755C or benoxaprofen. E-5110 also inhibited superoxide generation by human neutrophils stimulated with opsonized zymosan, f-Met-Leu-Phe and phorbol myristate acetate. These results indicate that E-5110 is a potent dual inhibitor that suppresses superoxide generation.

Animals↗