Abstract 489: Mechanisms of Carbon Monoxide Attenuation of Tubuloglomerular Feedback

Hypertension ◽  
2012 ◽  
Vol 60 (suppl_1) ◽  
Author(s):  
YiLin Ren ◽  
Martin A D'Ambrosio ◽  
Hong Wang ◽  
Jeffrey L Garvin ◽  
Oscar A Carretero
Keyword(s):  
Carbon Monoxide ◽  
Physiological Role ◽  
Inhibitory Effect ◽  
Tubuloglomerular Feedback ◽  
Renal Microcirculation ◽  
Low Concentrations ◽  
Cgmp Analog ◽  
Cell Depolarization ◽  
Toxic Concentrations

Tubuloglomerular feedback (TGF) is an autoregulatory mechanism of the renal microcirculation in which the macula densa (MD) senses NaCl concentration in the lumen of the nephron and sends a signal that controls glomerular filtration rate by constricting the afferent arteriole (Af-Art). We have shown that MD depolarization is sufficient for inducing TGF. Carbon monoxide (CO), either endogenous or exogenous, is known to inhibit TGF, at least in part via cGMP. However, whether cGMP-independent mechanisms are involved, and where in the TGF cascade CO exerts its inhibitory effect, remain unknown. Thus we hypothesize that CO, acting via both cGMP-dependent and -independent mechanisms, attenuates TGF by acting downstream from MD cell depolarization. In vitro , microdissected rabbit Af-Arts and their attached MD were simultaneously perfused and TGF was measured as the decrease in Af-Art diameter. Depolarization of the MD was induced by switching luminal KCl from 4 to 50 mM in the presence of the potassium ionophore valinomycin, while adding the CO-releasing molecule CORM-3 to the MD perfusate at non-toxic concentrations. CORM-3 blunted depolarization-induced TGF at a concentration of 50 μM, from 3.6±0.4 to 2.5±0.4 μm (P<0.01), and completely abolished it at a concentration of 100 μM, to 0.1±0.1 μm (P<0.001, n=6). Similar results were found with 100 μM CORM-3 when depolarization was induced by nystatin (3.0±0.2 vs. 0.4±0.2 μm, P <0.001, n=6). This indicates that CO inhibits TGF acting downstream from depolarization. When cGMP generation was blocked with the guanylate cyclase inhibitor LY-83583 (1 μM) added to the MD, CORM-3 no longer had an effect on depolarization-induced TGF at 50 μM (2.9±0.4 vs. 3.0±0.4 μm), but retained partial inhibitory effect on TGF at 100 μM (1.3±0.2 μm, P =0.02, n=9). This suggests that CO acts via cGMP at low concentrations, but additional mechanisms of action may be involved at higher concentrations. Finally, we confirmed that cGMP inhibits TGF downstream from MD depolarization by adding the degradation-resistant cGMP analog dibutyryl-cGMP (500 μM), which attenuated depolarization-induced TGF (from 3.9±0.5 to 0.6±0.2 μm, P <0.01, n=6). Our results could help explain the physiological role of CO in controlling the renal microcirculation.

In Vitro Effects of Ethanol on Rabbit Platelet Aggregation, Secretion of Granule Contents, and Cyclic AMP Levels in the Presence of Prostacyclin

1989 ◽  
Vol 61 (02) ◽  
pp. 254-258 ◽  
Author(s):  
Margaret L Rand ◽  
Peter L Gross ◽  
Donna M Jakowec ◽  
Marian A Packham ◽  
J Fraser Mustard
Keyword(s):  
Cyclic Amp ◽  
Inhibitory Effect ◽  
Rabbit Platelet ◽  
Inhibitory Effects ◽  
Low Concentrations ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
In Vitro Effects ◽  
Aggregation Of Platelets

SummaryEthanol, at physiologically tolerable concentrations, inhibits platelet responses to low concentrations of collagen or thrombin, but does not inhibit responses of washed rabbit platelets stimulated with high concentrations of ADP, collagen, or thrombin. However, when platelet responses to high concentrations of collagen or thrombin had been partially inhibited by prostacyclin (PGI2), ethanol had additional inhibitory effects on aggregation and secretion. These effects were also observed with aspirin- treated platelets stimulated with thrombin. Ethanol had no further inhibitory effect on aggregation of platelets stimulated with ADP, or the combination of ADP and epinephrine. Thus, the inhibitory effects of ethanol on platelet responses in the presence of PGI2 were very similar to its inhibitory effects in the absence of PGI2, when platelets were stimulated with lower concentrations of collagen or thrombin. Ethanol did not appear to exert its inhibitory effects by increasing cyclic AMP above basal levels and the additional inhibitory effects of ethanol in the presence of PGI2 did not appear to be brought about by further increases in platelet cyclic AMP levels.

Ticlopidine Selectively Inhibits Human Platelet Responses to Adenosine Diphosphate

1991 ◽  
Vol 66 (06) ◽  
pp. 694-699 ◽  
Author(s):  
Marco Cattaneo ◽  
Benjaporn Akkawat ◽  
Anna Lecchi ◽  
Claudio Cimminiello ◽  
Anna M Capitanio ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Adenosine Diphosphate ◽  
Inhibitory Effect ◽  
Clot Retraction ◽  
Fibrinogen Binding ◽  
Low Concentrations ◽  
Binding Inhibition ◽  
High Concentrations ◽  
Formalin Fixed

SummaryPlatelet aggregation and fibrinogen binding were studied in 15 individuals before and 7 days after the oral administration of ticlopidine (250 mg b.i.d.). Ticlopidine significantly inhibited platelet aggregation induced by adenosine diphosphate (ADP), the endoperoxide analogue U46619, collagen or low concentrations of thrombin, but did not inhibit platelet aggregation induced by epinephrine or high concentrations of thrombin. Ticlopidine inhibited 125I-fibrinogen binding induced by ADP, U46619 or thrombin (1 U/ml). The ADP scavengers apyrase or CP/CPK, added in vitro to platelet suspensions obtained before ticlopidine, caused the same pattern of aggregation and 125I-fibrihogen binding inhibition as did ticlopidine. Ticlopidine did not inhibit further platelet aggregation and 125I-fibrinogen binding induced in the presence of ADP scavengers. After ticlopidine administration, thrombin or U46619, but not ADP, increased the binding rate of the anti-GPIIb/IIIa monoclonal antibody 7E3 to platelets. Ticlopidine inhibited clot retraction induced by reptilase plus ADP, but not that induced by thrombin or by reptilase plus epinephrine, and prevented the inhibitory effect of ADP, but not that of epinephrine, on the PGE1-induced increase in platelet cyclic AMP. The number of high- and low-affinity binding sites for 3H-ADP on formalin-fixed platelets and their K d were not modified by ticlopidine. These findings indicate that ticlopidine selectively inhibits platelet responses to ADP.

Aromatase activity in the mare ovary during estrous cycle. Measurement of endogenous steroids and of their in vitro inhibitory effect

1993 ◽  
Vol 129 (6) ◽  
pp. 536-542 ◽  
Author(s):  
Hakima Amri ◽  
Pierre Silberzahn ◽  
Ihsan Al-Timimi ◽  
Jean-Luc Gaillard
Keyword(s):  
Follicular Fluid ◽  
Luteal Phase ◽  
Physiological Role ◽  
Inhibitory Effect ◽  
Aromatase Activity ◽  
Estrogen Production ◽  
Estrogen Synthesis ◽  
Luteal Tissue ◽  
Endogenous Steroids

This present study was undertaken to clarify estrogen synthesis in the mare ovary. First of all, an evaluation of endogenous steroid contents was carried out in the follicular fluid and in the luteal tissue at different stages of the luteal phase. Radioimmunoassays were performed after separation and purification of each hormone by chromatography. High amounts of conjugated (0.9 mg/l) and unconjugated (4 mg/l) estradiol-17β were found in the follicular fluid of the large follicules (50 mm). These concentrations of estrogens decreased drasticaly in the luteal tissue, and only low levels of circulating estrogens are found during the luteal phase. On the other hand, a high aromatization ability has been evidenced in the cyclic corpus luteum in vitro. In an attempt to clarify the regulation of estrogen synthesis, we have tested the inhibitory effect of several endogenous steroids on equine ovarian aromatase activity. 5α-Dihydrotestosterone appeared to be the most potent competitive inhibitor (Ki= 181 nmol/l) of aromatase activity, while the addition of a 3-sulfate group induced a slump in the inhibitory potency of estrone (Ki= 397 nmol/l vs 2206 nmol/l) and dehydroepiandrosterone (Ki = 291 nmol/l vs 6157 nmol/l). The physiological role of these conjugated steroids has not been known until now; we suggest that they would play a role in protecting aromatase from inhibition, in vivo. The high amounts of progesterone found in the luteal tissue (1.3 g/kg of proteins) might play a role in the regulation of estrogen production either by suppressing the induction of aromatase synthesis or by inhibiting the activity of the enzyme complex.

scholarly journals Studies on Analogues of L-Cysteine and L-Cystine

Blood ◽  
1956 ◽  
Vol 11 (1) ◽  
pp. 1-10 ◽  
Author(s):  
AUSTIN S. WEISBERGER ◽  
LEIF G. SUHRLAND ◽  
JOSEPH SEIFTER
Keyword(s):  
Amino Acids ◽  
Spatial Configuration ◽  
Spatial Relationship ◽  
Inhibitory Effect ◽  
Selenium Compounds ◽  
Low Concentrations ◽  
Relationship Of ◽  
Normal Cellular Function

Abstract The amino acids L-cysteine and L-cystine appear to have an important role in the metabolism of leukocytes. Decreased availability of these amino acids may therefore have important effects on leukocytes. The possibility of decreasing the influx of radioactive L-cystine into leukemic leukocytes was investigated by exposing the leukocytes to various analogues of cysteine (cystine) prior to incubation with S35 L-cystine. It was found that a highly specific structural and spatial configuration is required to decrease the influx of S35 L-cystine. Thus unlabeled L-cysteine is effective in decreasing the incorporation of radioactive L-cystine. However, analogues of cystine in which there is modification or substitution of the sulfhydryl, amino or carboxyl group do not decrease the influx of S35 L-cystine. Furthermore, any alteration in the spatial relationship of the sulfhydryl and amino groups of L-cysteine also results in a loss of the ability of an analogue to decrease the incorporation of S35 L-cystine. Of the compounds studied and in the concentrations employed, only unlabeled L-cysteine, selenium cystine and phenyl selenium cysteine were effective. Selenium cystine is identical with cystine except that selenium replaces the sulfur in the molecule. Phenyl selenium cysteine is also closely related structurally to cysteine. The mechanism of action of selenium cystine and phenyl selenium cysteine in decreasing the influx of S35 L-cystine is not known. Other selenium compounds tested were ineffective. These compounds may exert their inhibitory effect by (a) competitive combination with specific intracellular receptors for L-cysteine (L-cystine), (b) inactivation of enzymes or compounds essential for normal cellular function, (c) alteration in membrane permeability or (d) a toxic effect of selenium. Since selenium cystine and phenyl selenium cystine are inhibitory in low concentrations in vitro, these compounds may have important effects on leukemic leukocytes in vivo.

A novel mechanism of olanzapine-induced lipid accumulation

2011 ◽  
Vol 26 (S2) ◽  
pp. 906-906 ◽  
Author(s):  
S. Dzitoyeva ◽  
H. Chen ◽  
R. Manev ◽  
H. Manev
Keyword(s):  
Lipid Content ◽  
Direct Action ◽  
Inhibitory Effect ◽  
Experimental Conditions ◽  
Cell Content ◽  
Metabolic Alterations ◽  
Low Concentrations ◽  
Mrna Content ◽  
Quantitative Western Blot

IntroductionSecond generation antipsychotic drugs (SGADs) including olanzapine trigger adverse metabolic alterations possibly by a direct action on adipocytes.Objectives and aimsThe system of the inflammatory 5-lipoxygenase (5-LOX) and its activating protein (FLAP) have been implicated in lipid dysfunction in obesity. We investigated whether this system could participate in the adipogenic action of olanzapine.MethodsExperiments were performed in 3T3-L1 adipocytes in vitro. Cells were treated with olanzapine and a FLAP inhibitor MK-886. Their lipid content, 5-LOX and FLAP mRNA content, and FLAP protein content were measured.ResultsOlanzapine treatment did not affect the cell content of 5-LOX mRNA; however, it decreased FLAP mRNA content at day five but not 24 hours after olanzapine addition. The inhibitory effect of olanzapine on FLAP expression was confirmed by quantitative Western blot assays. In the absence of a FLAP inhibitor, low concentrations of olanzapine (0.5 and 5 μM) increased lipid content only by about 13% (compared to about a 56% increase induced by 50 μM olanzapine) whereas in the presence of MK-886 these concentrations of olanzapine produced lipid increases comparable to the increase caused by 50 μM. In these experimental conditions, MK-886 alone did not alter the cell content of lipids.Conclusions5-LOX system may be involved in lipid dysfunction not only in conditions of obesity but possibly in SGAD-related metabolic alterations. The known polymorphism in the genes of the human 5-LOX system could play a role in setting a variable individual susceptibility to the metabolic side effects of SGADs.

scholarly journals Effect of aluminium toxicity on the development of poplar (Populus tremula L. x P. alba L.) cultured in vitro

2014 ◽  
Vol 68 (4) ◽  
pp. 245-250 ◽  
Author(s):  
Krystyna Bojarczuk
Keyword(s):  
Aluminium Toxicity ◽  
Inhibitory Effect ◽  
Populus Tremula ◽  
Aluminium Chloride ◽  
Adventitious Bud ◽  
Aluminium Sulphate ◽  
Low Concentrations ◽  
The Media ◽  
High Concentrations

Adventitious bud cultures were established using vegetative buds from selected clones of poplar (<em>Populus tremula</em> L. x <em>P</em>. <em>alba</em> L.) as initial explants. For multiplication of shoots a modified Murashige and Skoog medium (MS) was used. Aluminium salts (aluminium sulphate and aluminium chloride) were added to the media. It was found that the pH of the medium had no effect on the development of cultures at low concentrations of nutrients (1/2 or 1/4 MS). Low concentrations of aluminium (Al 25mg•dm<sup>-3</sup> supplied as aluminium sulphate, Al 15 mg•dm<sup>-3</sup> as aluminium chloride) had no inhibitory effect on shoot development but decreased regeneration of adventitious roots. High concentrations of aluminium inhibited the development of shoots and roots, especially in a medium at pH 4.5. Microcuttings rooted in the highest percentage and formed the strongest rooting system on 1/4 strength MS medium at pH 4.5. It was found that there was no difference between the rooting of shoots excised from cultures cultivated with or without A1 in this medium at pH 5.5.

scholarly journals Invitro Toxicity of Binary Mixtures of Glyphosate and 2, 2 Dichlorovinyl Dimethyl Phosphate on Bacterial Isolates

2021 ◽  
pp. 36-48
Author(s):  
C. O. Anuniru ◽  
J. N. Ogbulie ◽  
C. C. Opurum ◽  
E. S. Asiwe
Keyword(s):  
Binary Mixtures ◽  
Bacterial Species ◽  
Aquatic Organisms ◽  
Inhibitory Effect ◽  
In Vitro Toxicity ◽  
Triphenyltetrazolium Chloride ◽  
Dimethyl Phosphate ◽  
Low Concentrations ◽  
Artificial Electron Acceptor

The in vitro toxicity of glyphosate (Gly) and 2, 2 Dichlorovinyl dimethyl phosphate (DDVP) single compound and binary mixtures was assessed against Pseudomonas sp. and Bacillus sp. isolated from Otamiri River, Imo state, Nigeria was investigated. The toxicity response was assessed using the inhibitory effect of the single and binary mixtures on isolates dehydrogenase activity; and 2,3,5 triphenyltetrazolium chloride (TTC) was used as the artificial electron acceptor. The binary mixtures were composed using fixed ratios of glyphosate and 2, 2 Dichlorovinyl dimethyl phosphate in ratios of 20% Gly:80% DDVP, 40% Gly: 60% DDVP, 50% Gly: 50% DDVP, 60% Gly: 40% DDVP and 80% Gly: 20% DDVP. Results obtained showed that the isolates exhibited different degrees of logistic and sigmoidal toxicity trends with areas of hormesis at low concentrations of the toxicants. Furthermore, isobolographic analysis on the toxic interaction of the mixtures presented both synergism and antagonism, based on the relative ratio of the component mixtures. Increasing concentration of glyphosate in the binary mixture caused a shift in the interaction effect from antagonism to synergism. Our findings showed that isolates exhibited tolerance to glyphosate and 2,2 dichlorovinyl dimethyl phosphate and their binary mixtures exposure at concentration range of 0-1000mg/L; above which has deleterious effects on the aquatic organisms. It is evident that there are considerable differences in pesticide sensitivity among the bacterial species and that the presence of glyphosate and 2, 2-dichlorovinyl dimethyl phosphate in the aquatic environment may present toxicological risk to microbial diversity.

Accumulation of Unphosphorylated Calponin in the Submembranous Cytoskeletons of Arachidonic Acid-stimulated Human Platelets

1996 ◽  
Vol 75 (04) ◽  
pp. 617-622 ◽  
Author(s):  
Thomas Meyer ◽  
Christina Unterberg ◽  
Heinrich Kreuzer ◽  
Arnd B Buchwald
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase ◽  
Muscle Protein ◽  
Physiological Role ◽  
Protein Band ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Calpain Inhibitor ◽  
Dependent Protein

SummaryCalponin, a basic smooth-muscle protein capable of binding to F-actin, tropomyosin and calmodulin in vitro, was tested for its expression and subcellular localization in resting and stimulated human platelets. Using immunoblotting techniques calponin was revealed as a single protein band with a molecular weight of 34 kDa. Although calponin has been shown to be proteolytically degraded by calpain, in the presence of the calpain inhibitor E-64 and EGTA a significant hydrolysis of calponin could not be detected. Upon stimulation with 10 μM arachidonic acid calponin became increasingly incorporated into Triton X-100 insoluble cytoskeletal fractions reaching a plateau after 15 s. The accumulation of calponin in the cytoskeletons of stimulated platelets paralleled the polymerization of actin into newly formed microfilaments. Immunofluorescence microscopy revealed a sub-membranous co-localization of calponin and actin in aggregated platelets. Since isolated calponin is phosphorylated by protein kinase C and Ca2+/calmodulin-dependent protein kinase II thereby losing its inhibitory effect on the actomyosin MgATPase activity, we examined whether changes in cell shape due to platelet stimulation are accompanied by a phosphorylation of calponin. By performing immunoblotting analysis on either resting or stimulated platelets phosphorylation of calponin on tyrosine, serine or threonine residues could not be demonstrated. In line, [32P]radiolabeling experiments were unable to detect phosphate incorporation into calponin. These observations support the hypothesis that calponin plays a physiological role in regulating contraction and secretion of human platelets even in the absence of its phosphorylation.

Regulation of Thromboplastin Synthesis in Mouse Placental Cells In Vitro

1983 ◽  
Vol 50 (04) ◽  
pp. 831-834 ◽  
Author(s):  
Knut Dalaker ◽  
Hans Prydz
Keyword(s):  
Cyclic Amp ◽  
Phosphodiesterase Inhibitor ◽  
Inhibitory Effect ◽  
Low Concentrations ◽  
Placental Cells ◽  
Dose Dependent ◽  
Higher Doses ◽  
Dose Dependent Effect ◽  
Methyl Xanthine

SummaryMouse placental cells are probably constitutive producers of the thromboplastin apoprotein in vitro. The effect of cyclic AMP- elevating compounds on their expression of thromboplastin activity has been studied. Dibutyryl cyclic AMP, the phosphodiesterase inhibitor Ro 20-1724 and the adenyl cyclase stimulator forskolin all decrease the synthesis of thromboplastin. Prostaglandin E2 and the phosphodiesterase inhibitor butyl-methyl-xanthine have a biphasic dose dependent effect. A stimulation was observed at low concentrations, whereas higher doses decreased the synthesis of thromboplastin. Adrenaline had no effect. Combination of two compounds, each at maximally inhibiting concentration gave no significant additive inhibitory effect, showing that they probably act via the same pathway.

Extracellular Nucleoside Diphosphate Kinase NDPK/Nm23 Protein Isoforms A and B Support Erythropoiesis and Have a Burst-Promoting Activity.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1625-1625
Author(s):  
Zwi N. Berneman ◽  
Roel Willems ◽  
Griet Nijs ◽  
Marc Lenjou ◽  
Dirk R. Van Bockstaele
Keyword(s):  
Physiological Role ◽  
Nucleoside Diphosphate Kinase ◽  
Fold Increase ◽  
Protein Isoforms ◽  
Bone Marrow Mononuclear Cell ◽  
Gm Csf ◽  
Low Concentrations ◽  
High Concentrations ◽  
Macrophage Colony

Abstract We previously demonstrated the in vitro hematopoietic effects of different nucleoside diphosphate kinase NDPK/Nm23 proteins, i.e. increase of burst-forming units erythroid (BFU-E) and decrease of colony-forming units macrophage (CFU-M) (Willems R et al. Experimental Hematology2002;30: 640–648). The effect was especially pronounced in the marrows that had a particular low BFU-E count. Since these experiments were performed under optimal erythroid growth factor stimulation including adequately high concentrations of erythropoietin (Epo) and stem cell factor (SCF 100 ng/mL), subtle effects of NDPK/Nm23 proteins on erythropoiesis could have been missed. In the present series of experiments on 7 normal bone marrow mononuclear cell suspensions, we deliberately created suboptimal in vitro conditions for early (BFU-E) erythropoiesis: i.e. serum free conditions with a limited number of cytokines (only Epo and SCF) and a low concentration of burst-promoting activity (SCF at 5 ng/ml). The results show that addition of NDPK A/Nm23-H1 and NDPK B/Nm23- H2 (but not of NDPK C) at high (40 μg/mL), but not low, extracellular concentration is sustaining and improving in vitro erythropoiesis in a statistically significant manner (P<0.05). Red cell colonies increased by a factor of 1.9 and 1.4 following addition of NDPK A/Nm23-H1 and NDPK B/Nm23- H2 respectively. Especially with NDPK A/Nm23-H1, this approaches levels attained under optimal conditions for erythropoiesis, i.e. at SCF concentration of 100 ng/mL, where a 2.1-fold increase was seen, as compared to cultures with low concentrations of SCF (5 ng/mL) without addition of extracellular NDPK/Nm23. In cultures without Epo no erythroid colonies were seen, even following addition of NDPK A/Nm23-H1 or NDPK B/Nm23-H2. This study strongly suggests that NDPK/Nm23 has a burst-promoting activity. The fairly high concentrations of NDPK/Nm23 constitutively present in plasma supports the physiological role of this protein in stimulating early erythropoiesis. Of the (known) cytokines or proteins with burst-promoting activity (eg. SCF, interleukin 3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), NDPK/Nm23 (this study)), only SCF and NDPK/Nm23 are produced in a constitutive fashion, strongly supporting their role in the steady-state support of early erythropoiesis.

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