Biomedical subjects

K Török

Publications and source records attributed to K Török.

At least 19 recordsLinked to original sources

PubMed2004

Anti-inflammatory effect and soft properties of etiprednol dicloacetate (BNP-166), a new, anti-asthmatic steroid.

In vitro and in vivo anti-inflammatory properties and soft characteristics of etiprednol dicloacetate (BNP-166) a new steroid, which has been developed for the treatment of asthma, were investigated in this study. The compound effectively decreased cytokine production in lipopolysaccharide stimulated lymphocytes and attenuated lectin-induced proliferation of blood mononuclear cells in tissue culture. In an animal model of allergen sensitized and challenged Brown Norway rats, using topical treatment, etiprednol dicloacetate substantially attenuated the extent of allergen induced bronchoalveolar fluid eosinophilia. At every examined parameter its pharmacological effects were comparable to those of budesonide. By means of in vitro biological and analytical methods the soft character of BNP-166 was also investigated. The anti-inflammatory effect of etiprednol dicloacetate in vitro was shown to be the function of the quantity of serum components, present in the assay. This loss of activity was most likely the result of the fast metabolism of etiprednol dicloacetate, which in the presence of sera could have been demonstrated by LC/MS/MS. Our data indicate that the significant local effect of the compound will very likely be accompanied with a drastically reduced systemic activity indicating an encouraging selectivity of the pharmacological action of etiprednol dicloacetate.

Adrenal Cortex Hormones↗

PubMed2002

Calmodulin conformational changes in the activation of protein kinases.

The conformation of Ca2+/calmodulin changes from extended when free in solution to compact when bound in peptide complexes. The extent and kinetics of calmodulin compaction in association with Ca2+/calmodulin-dependent protein kinases (CaMKs), as well as target peptides, were investigated by fluorescence, resonance energy transfer and stopped-flow kinetics. Compaction of Ca2+/calmodulin labelled with resonance energy-transfer probes in association with target peptides was rapid (>350 s(-1)). With the target enzymes smooth-muscle myosin light-chain kinase, CaMKIV and CaMKII, the rates of calmodulin compaction were one-two orders of magnitude lower compared with those of the peptides and in the case of alphaCaMKII, ATP binding and Thr(286) auto-phosphorylation were required for calmodulin compaction. In the absence of nucleotides, Ca2+/calmodulin bound to alphaCaMKII in extended conformations, initially probably attached by one lobe only. Kinetic data suggest that in the activation process of Ca2+/calmodulin-dependent protein kinases, productive as well as unproductive complexes are formed. The formation of productive complexes with Ca2+/calmodulin thus may determine the rate of activation.

Animals↗

PubMed2001

Dual effect of ATP in the activation mechanism of brain Ca(2+)/calmodulin-dependent protein kinase II by Ca(2+)/calmodulin.

The activation mechanism of Ca(2+)/calmodulin-dependent protein kinase II (alphaCaMKII) is investigated by steady-state and stopped-flow fluorescence spectroscopies. Lys(75)-labeled TA-cal [Török, K., and Trentham, D. R. (1994) Biochemistry 33, 12807-12820] is used to measure binding events, and double-labeled AEDANS,DDP-T34C/T110/C-calmodulin [Drum et al. (2000) J. Biol. Chem. 275, 36334-36340] (DA-cal) is used to detect changes in calmodulin conformation. Fluorescence quenching of DA-cal attributed to resonance energy transfer is related to the compactness of the calmodulin molecule. Interprobe distances are estimated by lifetime measurements of Ca(2+)/DA-cal in complexes with unphosphorylated nucleotide-free, nucleotide-bound, and Thr(286)-phospho-alphaCaMKII as well as with alphaCaMKII-derived calmodulin-binding peptides in the presence of Ca(2+). These measurements show that calmodulin can assume at least two spectrally distinct conformations when bound to alphaCaMKII with estimated interprobe distances of 40 and 22-26 A. Incubation with ATP facilitates the assumption of the most compact conformation. Nonhydrolyzable ATP analogues partially replicate the effects of ATP, suggesting that while the binding of ATP induces a conformational change, Thr(286)-autophosphorylation is probably required for the transition of calmodulin into its most compact conformer. The rate constant for the association of Ca(2+)/TA-cal with alphaCaMKII is estimated as 2 x 10(7) M(-1) s(-1) and is not substantially affected by the presence of ATP. The rate of net calmodulin compaction measured by Ca(2+)/DA-cal is markedly slower, occurring with a rate constant of 2.5 x 10(6) M(-1) s(-1), suggesting that unproductive complexes may play a role in the activation mechanism.

Adenosine Triphosphate↗

PubMed2001

Oligomeric structure of alpha-calmodulin-dependent protein kinase II.

The subunit stoichiometry and symmetry of the neuronal alpha-calmodulin-dependent protein kinase II (alphaCaMKII) is investigated in this report to understand the structural basis of its regulation and mechanism at the molecular level. Two preparations are studied, alphaCaMKII obtained by overexpression in baculovirus-transfected insect cells and CaMKII isolated from rat forebrain. The structures, are studied by electron microscopy and image analysis. Single-particle analysis of individual molecular images reveals a molecule with a circular outline and pronounced 6-fold rotational symmetry of the central part. The central part has an outer radius of approximately 6 nm and is composed of six lobes grouped around a hollow centre. The outer ring extends to approximately 15 nm and consists of 12 apparent domains. These data are interpreted in terms of a three-dimensional model of the alphaCaMKII complex consisting of 12 subunits, each corresponding to a single alphaCaMKII polypeptide chain. The inner ring corresponding to approximately one-third of the molecular mass of the complex is made up of the C-terminal association domains. The 12 association domains are arranged in two concentric hexagonal rings at different axial levels and in rotational register. The outer ring corresponding to the remaining molecular mass of the complex is made up of the 12 N-terminal catalytic domains located at an axial level halfway between the two levels of the association domains. The 6-fold symmetry of stacked association domains may derive from subunit arrangements corresponding to either the C6 or the D6 point group symmetries. The symmetry and the resulting subunit arrangement define the pattern and extent of regulatory autophosphorylation within the alphaCaMKII complex.

Animals↗

PubMed2001

Low physical performance in obese adolescent boys with metabolic syndrome.

OBJECTIVE: To assess cardiorespiratory exercise function in obese children with and without metabolic syndrome (MS). DESIGN: Comparing three groups of subjects with different cardiovascular risk profiles. SUBJECTS: Twenty-two MS (body weight (mean+/-s.d.) 97.3+/-15.3 kg; age (mean+/-s.d.) 14.2+/-1.9 y), 17 obese (82.6+/-15.7 kg; 14.2+/-2.6 y) and 29 normal weight control (64.3+/-8.5 kg; 15.3+/-1.0 y) boys. MEASUREMENTS: Exercise duration (ED), resting heart rate (HR(0)), peak heart rate (HR(peak)), physical working capacity at 170 beat/min (PWC-170), peak oxygen consumption (VO(2peak)) and the lactic acidosis threshold (LAT) were determined on treadmill, using a continuous ramp protocol. RESULTS: ED (MS (mean+/-s.d.); 655+/-86 s; obese 703+/-64 s; control 750+/-0 s) in absolute value and PWC-170 normalised for body weight (139+/-40 w; 177+/-40 w; 211+/-40 w) were significantly shorter and lower in the MS group, as compared to obese and control groups (P<0.05). VO(2peak) (2.2+/-0.4 l/min; 2.4+/-0.5 l/min; 2.9+/-0.4 l/min) and LAT (1.3+/-0.4 l/min; 1.5+/-0.4 l/ min; 1.8+/-0.4 l/min) normalised for body weight, were significantly shorter and lower in the MS group, as compared to control group (P<0.05). HR(0) was significantly higher (P<0.05) in MS group than in obese and control groups (88+/-12 bpm; obese 78+/-10 bpm; 73+/-10 bpm). CONCLUSION: Cardiorespiratory exercise performance capacity in MS boys are reduced. It still remains to be elucidated whether the metabolic alterations or the decreased physical activity is responsible for the observed reduction in cardiorespiratory performance.

Acidosis, Lactic↗

PubMed2001

Auxin and heat shock activation of a novel member of the calmodulin like domain protein kinase gene family in cultured alfalfa cells.

A calmodulin like domain protein kinase (CPK) homologue was identified in alfalfa and termed MsCPK3. The full-length sequence of cDNA encoded a 535 amino acid polypeptide with a molecular weight of 60.2 kDa. The deduced amino acid sequence showed all the conserved motifs that define other members of this kinase family, such as serine-threonine kinase domain, a junction region and four potential Ca2+ -binding EF sites. The recombinant MsCPK3 protein purified from E. coli was activated by Ca2+ and inhibited by calmodulin antagonist (W-7) in in vitro phosphorylation assays. The expression of MsCPK3 gene increased in the early phase of the 2,4-D induced alfalfa somatic embryogenesis. Heat shock also activated this gene while kinetin, ABA and NaCl treatment did not result in MsCPK3 mRNA accumulation. The data presented suggest that the new alfalfa CPK differs in stress responses from the previously described homologues and in its potential involvement in hormone and stress-activated reprogramming of developmental pathways during somatic embryogenesis.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2000

Ca2+-calmodulin inhibits Ca2+ release mediated by type-1, -2 and -3 inositol trisphosphate receptors.

InsP(3) binding to type-1, but not type-3, InsP(3) receptors is inhibited by calmodulin in a Ca(2+)-independent fashion [Cardy and Taylor (1998) Biochem. J. 334, 447-455], and Ca(2+) mobilization by type-1 InsP(3) receptors of cerebellum is inhibited by calmodulin [Patel, Morris, Adkins, O'Beirne and Taylor (1997) Proc. Natl. Acad. Sci. U.S.A. 94, 11627-11632]. Using cell types expressing predominantly type-1, -2 or -3 InsP(3) receptors, we show that InsP(3)-evoked Ca(2+) mobilization from each is similarly inhibited by calmodulin. In SH-SY5Y cells, which express largely type-1 receptors, calmodulin (IC(50) approximately 15 microM) inhibited InsP(3)-evoked Ca(2+) release only in the presence of Ca(2+). The inhibition was unaffected by calcineurin inhibitors. The effect of calmodulin did not result from enhanced metabolism of InsP(3) because calmodulin also decreased the sensitivity of the Ca(2+) stores to adenophostin A, a non-metabolizable InsP(3)-receptor agonist. Protein kinase A-catalysed phosphorylation of type-1 InsP(3) receptors was unaffected by Ca(2+)-calmodulin. Using a scintillation proximity assay to measure (125)I-calmodulin binding to glutathione S-transferase-fusion proteins, we identified two regions of the type-1 InsP(3) receptor (cyt1, residues -6 to 159; and cyt11, residues 1499-1649) that bound (125)I-calmodulin. The higher-affinity site (cyt11) was also photoaffinity labelled with N-hydroxysuccinimidyl-4-azidobenzoate (HSAB)-calmodulin. We speculate that Ca(2+)-independent binding of calmodulin to a site within the first 159 residues of the type-1 InsP(3) receptor inhibits InsP(3) binding and may thereby regulate the kinetics of Ca(2+) release. Ca(2+)-dependent inhibition of Ca(2+) release by calmodulin is mediated by a different site: it may reside on an accessory protein that associates with all three receptor subtypes, or Ca(2+)-calmodulin binding to a site lying between residues 1499 and 1649 of the type-1 receptor may inhibit Ca(2+) release from any tetrameric receptor that includes a type-1 subunit.

Adenosine↗

PubMed2000

Polyunsaturated fatty acids in plasma lipids of obese children with and without metabolic cardiovascular syndrome.

Previously we reported significantly higher values of gamma-linolenic acid (GLA, 18:3n-6), dihomo-gamma-linolenic acid (DHGLA, 20:3n-6), and arachidonic acid (20:4n-6) in plasma lipid classes in obese children than in nonobese controls. In the present study, fatty acid composition of plasma phospholipids (PL) and sterol esters (STE) was determined by high-resolution capillary gas-liquid chromatography in obese children with and without metabolic cardiovascular syndrome [MCS: defined as simultaneous presence of (i) dyslipidemia, (ii) hyperinsulinemia, (iii) hypertension, and.(iv) impaired glucose tolerance] and in nonobese controls. Fatty acid composition of PL and STE lipids did not differ between obese children without MCS and controls. Obese children with MCS exhibited significantly lower linoleic acid (LA, 18:2n-6) values in PL (17.43 [2.36], % wt/wt, median [range from the first to the third quartile]) than obese children without MCS (19.14 [3.49]) and controls (20.28 13.80]). In contrast, PL GLA values were significantly higher in obese children with (0.13 [0.08]) than in those without MCS (0.08 [0.04]), whereas STE GLA values were higher in obese children with MCS (1.04 [0.72]) than in controls (0.62 [0.48]). DHGLA values in PL were significantly higher in obese children with MCS (4.06 [0.74]) than in controls (2.69 [1.60]). The GLA/LA ratio was significantly higher, whereas the AA/DHGLA ratio was significantly lower in obese children with MCS than in obese children without MCS and in controls. In this study, LA metabolism was affected only in obese children with but not in those without MCS. In obese children with MCS, delta6-desaturase activity appeared to be stimulated, whereas delta5-desaturase activity appeared to be inhibited. Disturbances in LA metabolism may represent an additional health hazard within the multifaceted clinical picture of MCS.

Adolescent↗

PubMed2000

Safety and efficacy of treatment with an ephedrine/caffeine mixture. The first double-blind placebo-controlled pilot study in adolescents.

OBJECTIVE: The present study was performed to investigate the efficacy and safety of a caffeine/ephedrine (CE) mixture in obese adolescents. SUBJECTS: Thirty-two (m/f = 16/16) obese children were included into the study. They were treated by diet (calculated daily energy requirement minus 500 kcal) and either CE or placebo (PL) for 20 weeks in a randomized double-blind placebo-controlled trial. Those weighing less than 80 kg took one tablet three times (100 mg/10 mg), whereas those weighing more than 80 kg took two tablets three times per day. There were three dropouts (girls) from the PL group. The age, weight body mass index (BMI) values (mean (range)) of the PL and CE groups were 16.0 (14.3-17.6) and 16.0 (14.2-17.7) y, 103.0 (77.2-126.4) and 104.8 (69.8-150.2) kg, 35.2 (28.3-42.3) and 36.5 (31.3-51.8) kg/m2, respectively. RESULTS: The decrease in relative body weight, BMI and body fat (measured by bioelectric impedance) was significantly (P < 0.05) greater in the CE group (mean +/- s.d.; 14.4 +/- 10.5%, 2.9 +/- 1.9 kg/m2, 6.6 +/- 6.0 kg) than in the PL group (2.2 +/- 5.8%, 0.5 +/- 1.6 kg/m2, 0.5 +/- 2.7 kg). Relative body weight decreased by more than 5% in 81% of the CE group, out only in 31% of the PL group. Adverse events were negligible and did not differ between the CE and PL groups. Withdrawal symptoms were mild, transient and their frequency and severity were not different between the placebo and active groups. CONCLUSION: According to the present pilot study, CE can be a safe and effective compound for the treatment of obesity in adolescents.

Adipose Tissue↗

PubMed2000

A novel aldose/aldehyde reductase protects transgenic plants against lipid peroxidation under chemical and drought stresses.

Rapid accumulation of toxic products from reactions of reactive oxygen species (ROS) with lipids and proteins significantly contributes to the damage of crop plants under biotic and abiotic stresses. Here we have identified a stress-activated alfalfa gene encoding a novel plant NADPH-dependent aldose/aldehyde reductase that also exhibited characteristics of the homologous human enzyme. The recombinant alfalfa enzyme is active on 4-hydroxynon-2-enal, a known cytotoxic lipid peroxide degradation product. Ectopic synthesis of this enzyme in transgenic tobacco plants provided considerable tolerance against oxidative damage caused by paraquat and heavy metal treatment. These transformants could also resist a long period of water deficiency and exhibited improved recovery after rehydration. We found a reduced production of lipid peroxidation-derived reactive aldehydes in these transformed plants under different stresses. These studies reveal a new and efficient detoxification pathway in plants.

Adaptation, Physiological↗

PubMed2000

Calmodulin regulates the disassembly of cortical F-actin in mast cells but is not required for secretion.

Secretion is dependent on a rise in cytosolic Ca(2+)concentration and is associated with dramatic changes in actin organization. The actin cortex may act as a barrier between secretory vesicles and plasma membrane. Thus, disassembly of this cortex should precede late steps of exocytosis. Here we investigate regulation of both the actin cytoskeleton and secretion by calmodulin. Ca(2+), together with ATP, induces cortical F-actin disassembly in permeabilized rat peritoneal mast cells. This effect is strongly inhibited by removing endogenous calmodulin (using calmodulin inhibitory peptides), and increased by exogenous calmodulin. Neither treatment, however, affects secretion. Low concentrations ( approximately 1 microM) of a specific inhibitor of myosin light chain kinase, ML-7, prevent F-actin disassembly, but not secretion. In contrast, a myosin inhibitor affecting both conventional and unconventional myosins, BDM, decreases cortical disassembly as well as secretion. Observations of fluorescein-calmodulin, introduced into permeabilized cells, confirmed a strong (Ca(2+)-independent) association of calmodulin with the actin cortex. In addition, fluorescein-calmodulin enters the nuclei in a Ca(2+)-dependent manner. In conclusion, calmodulin promotes myosin II-based contraction of the membrane cytoskeleton, which is a prerequisite for its disassembly. The late steps of exocytosis, however, require neither calmodulin nor cortical F-actin disassembly, but may be modulated by unconventional myosin(s).

Actins↗

PubMed1999

[Role of intrauterine growth in later cardiovascular risk factors in children 6-10 years of age].

There has been considerable interest in the possibility that prenatal events could influence the adult life. Adults who were small at birth have been reported to have higher blood pressure and increased risk of death from ischaemic heart disease, although there are some contradictory results. The aim of the present study was to determine the association between size at birth and later risk factors (hypertension, hyperinsulinism, hyperglycaemia and dyslipidaemia) in prepubertal children. The authors examined 205 children (121 boys, 84 girls) at the age of 6-10. They compared children born full term with normal weight, height and head circumference (1st group), the children born full term with birthweight, height and head circumference less than 10th centile (2nd group), children born full term with birthweight less than 10th centile and with normal length and head circumference (3rd group) and children who were preterm at birth (4th group). The age of children at the time of investigation was comparable in the four groups. Weight and height of the children in the 2nd group were significantly lower than in the 1st and 4th groups (2nd group vs 4th group: p < 0.01; 2nd group vs 1st group: p < 0.001). Dyslipidaemia was found 21% in the 1st group, 17% in the 2nd group, 16% in the 3rd group and 28% in prematures. The mean of the systolic and diastolic blood pressures were similar in the four groups. Hypertension was 12.5% in the 1st and 3rd groups, 5.6% in the 2nd group and 8.9% among prematures. According to the results cardiovascular risk factors can not be proved among children at the age of 6-10 who were born with low birthweight. Further studies are required to determine whether which stage of pregnancy might influence birthweight and later risk factors.

Adolescent↗

PubMed1999

Hormone-induced secretory and nuclear translocation of calmodulin: oscillations of calmodulin concentration with the nucleus as an integrator.

Many important enzyme activities are regulated by Ca2+-dependent interactions with calmodulin (CaM). Some of the most important targets for CaM action are in the nucleus, and Ca2+-dependent CaM translocation into this organelle has been reported. Hormone-evoked cytosolic Ca2+ signals occur physiologically as oscillations, but, so far, oscillations in CaM concentration have not been described. We loaded fluorescent-labeled CaM into pancreatic acinar cells and monitored the fluorescence in various regions by confocal microscopy. Sustained high concentrations of the hormone cholecystokinin or the neurotransmitter acetylcholine evoked a transient movement of cytosolic CaM from the basal nonnuclear area into the secretory granule region and, thereafter, a more substantial and prolonged translocation of CaM into the nucleoplasm. About 50% of the CaM that bound Ca2+ translocated. At a lower hormone concentration, evoking Ca2+ oscillations, regular spikes of increased CaM concentration were seen in the secretory granule region with mirror image spikes of decreased CaM concentration in the basal nonnuclear region. The nucleus was able to integrate the Ca2+ spike-evoked pulses of CaM translocation into a sustained elevation of the nucleoplasmic concentration of this protein.

Acetylcholine↗

PubMed1999

Plants ectopically expressing the iron-binding protein, ferritin, are tolerant to oxidative damage and pathogens.

Transgenic tobacco plants that synthesize alfalfa ferritin in vegetative tissues--either in its processed form in chloroplasts or in the cytoplasmic nonprocessed form--retained photosynthetic function upon free radical toxicity generated by iron excess or paraquat treatment. Progeny of transgenic plants accumulating ferritin in their leaves exhibited tolerance to necrotic damage caused by viral (tobacco necrosis virus) and fungal (Alternaria alternata, Botrytis cinerea) infections. These transformants exhibited normal photosynthetic function and chlorophyll content under greenhouse conditions. We propose that by sequestering intracellular iron involved in generation of the very reactive hydroxyl radicals through a Fenton reaction, ferritin protects plant cells from oxidative damage induced by a wide range of stresses.

Alternaria↗

PubMed1999

[Microscopic study of dental calculus in cadavers from the 18th-19th centuries].

The authors studied the dental calculus of 20 mummies with ligth microscopy, polarized ligth microscopy and scanning electron microscopy. Gram positive bacteria could be detected in all preparates, while Gram negative bacteria in 12 and fungi only in 3 dental calculus was visible. Animal food remains within five, and plant remains in all dental calculus were identified. Anorgic element and cell debris were seen in all preparates.

Adult↗

PubMed1998

Imaging the spatial dynamics of calmodulin activation during mitosis.

BACKGROUND: Calcium is an important and ubiquitous signalling ion. In most cell types, changes in intracellular calcium concentrations are sensed by calmodulin, a signal transduction protein that regulates cell function through its interactions with kinases and phosphatases. Calcium signals show complex spatiotemporal patterning, but little, if anything, is known about the patterns of calmodulin activation inside cells. RESULTS: We have measured calmodulin activation continuously during mitosis in living cells with a new probe, a fluorescent adduct of calmodulin termed TA-calmodulin. We found that calmodulin was activated locally and episodically in the nucleus and mitotic spindle. The pattern of calmodulin activation was different from the pattern of calcium signals and could not be predicted from the pattern of calcium increase. Calmodulin activation was essential for mitotic progression: both entry into mitosis and exit from mitosis were blocked by a novel peptide that bound to calmodulin with high affinity and so prevented the interaction of calmodulin with its target proteins. CONCLUSIONS: These data suggest that calmodulin regulates mitotic transitions and demonstrate the utility of fluorescent adducts for studying protein activation in living cells with good temporal and spatial resolution.

Animals↗

PubMed1998

Inhibition of calmodulin-activated smooth-muscle myosin light-chain kinase by calmodulin-binding peptides and fluorescent (phosphodiesterase-activating) calmodulin derivatives.

Aspects of the biochemistry of calmodulin have been addressed that bear on its cell biological role as a mediator of Ca2+ regulation. Calmodulin-binding peptides derived from the amino acid sequence of smooth-muscle myosin light-chain kinase (MLCK) were characterized as inhibitors of calmodulin activation of MLCK-catalyzed phosphorylation of the smooth-muscle regulatory light chain (MLC). MLCK activity was determined by measuring the rate of formation of one of the reaction products, ADP, in a coupled enzymatic assay by continuous fluorimetric monitoring of NADH removal in 100 microM CaCl2 at ionic strength 0.15 M, pH 7.0 and 21 degreesC. The Km value of calmodulin was 3.5 nM, a value 16-35-fold greater than the Kd value of calmodulin for MLCK [Török, K., and Trentham D. R. (1994) Biochemistry 33, 12807-12820]. The different Km and Kd values are most likely associated with the rate-limiting step in MLC phosphorylation being associated with product release from MLCK. The values of the inhibition constants, Ki, were the following: Ac-R-R-K-W-Q-K-T-G-H-A-V-R-A-I-G-R-L-CONH2 (Trp peptide), 8.6 (+/-1. 4 sd) pM; Y4-analogue of Trp peptide (Tyr peptide), 7.3 (+/-0.1) nM; and A-R-R-K-W-Q-K-T-G-H-A-V-R-A-I-G-R-L-S-S (RS20-like peptide), 0. 11-0.39 nM. The Ki values were consistent with kinetically determined Kd values of the peptides to calmodulin. Kinetic determination of Kd values required the use of a fluorescently labeled calmodulin, 2-chloro-(epsilon-amino-Lys75)-[6-(4-N, N-diethylamino-phenyl)-1,3,5-triazin-4-yl]-calmodulin (TA-calmodulin).1 Since, as here, Lys75 is a convenient labeling site on calmodulin for the introduction of fluorescent probes, the biological activity of the Lys-modified calmodulins was evaluated. TA-calmodulin and calmodulin selectively modified by 1-N, N-dimethylaminonaphthalene-5-sulfonyl chloride (dansyl-C1) at Lys75 (dansyl-calmodulin) were characterized as activators of cyclic AMP phosphodiesterase (PDE) and inhibitors of MLCK. The Km value for dansyl-calmodulin was equal to that of calmodulin, and that of TA-calmodulin was 3.5-fold greater. TA-calmodulin and Lys75-labeled dansyl-calmodulin thus distinguish between PDE and MLCK being agonists to the former and antagonists to the latter.

Amino Acid Sequence↗

PubMed1997

Apparent antinociceptive and anti-inflammatory effects of GYKI 52466.

GYKI 52466 (1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine) was examined in a battery of analgesia and anti-inflammatory tests in rats and mice, respectively. Its 3-N-acetyl (GYKI 53773) and 3-N-methylcarbamoyl (GYKI 53784) derivatives were also examined in some assays. These 2,3-benzodiazepines, known as prototypic non-competitive antagonists of AMPA receptors, showed a peculiar profile in some routinely used antinociceptive tests. They were found fairly potent in rat tail flick and mouse phenylquinone writhing assays but the dose-response curves were rather shallow as compared to that of morphine. Their action is stereoselective, i.e., the (+) isomers were found inactive, in agreement with the previous in vitro studies. Their antinociceptive effect could not be reversed by naloxone and the GYKI compounds did not potentiate significantly the morphine-induced analgesia. In the mouse hot plate assay the 2,3-benzodiazepines were active only in doses inducing visible motor incapacitation. In rats, GYKI 52466 weakly reduced the hypersensitivity accompanying acute carrageenan edema. However, it potently inhibited the hyperalgesia during Freund adjuvant-induced chronic arthritis. In the latter assay GYKI 52466 also attenuated the body weight loss without altering the paw edema. The present findings confirm reports in the literature which indicate AMPA receptors may contribute to certain forms of pathological hyperalgesia, e.g., to that detectable in inflamed tissues.

Acetaminophen↗