scholarly journals Effects of penicillins and 6-aminohexanoic acid on the kinetics of human plasmin

1989 ◽  
Vol 260 (2) ◽  
pp. 609-612 ◽  
Author(s):  
A A A Higazi ◽  
M Mayer
Keyword(s):  
Active Site ◽  
Dependent Manner ◽  
Chromogenic Substrate ◽  
Regulatory Site ◽  
Amidolytic Activity ◽  
Plasmin Activity ◽  
Maximal Inhibition ◽  
Sigmoidal Curve ◽  
Kinetics Of ◽  
Dose Dependent

Human plasmin activity is inhibited by various penicillins in a dose-dependent manner. Ampicillin and cloxacillin produce a 50% inhibition of the globinolytic activity of plasmin at 4.5 and 5.3 mM respectively. A lower inhibitory capacity is displayed by carbenicillin. Assay of plasmin by its amidolytic activity on D-valyl-L-leucyl-L-lysine p-nitroanilide dihydrochloride showed that ampicillin at a concentration producing half-maximal inhibition converted the hyperbolic activity-substrate concentration curve into a sigmoidal curve. A similar conversion occurred in the presence of ampicillin when plasmin was assayed with an alternative chromogenic substrate, L-pyroglutamyl-glycyl-L-arginine p-nitroanilide hydrochloride 6-Aminohexanoic acid at 7.5 microM abolished the inhibition of plasmin induced by ampicillin. The present observations suggest that ampicillin interacts with plasmin at a regulatory site different from the active site of the enzyme. The effect of 6-aminohexanoic acid indicates that the lysine-binding site may be part of a regulatory site. It is possible that modulation of plasmin activity by ligands plays a role in the control of fibrinolysis.

scholarly journals Kinetics of Mushroom Tyrosinase and Melanogenesis Inhibition byN-Acetyl-pentapeptides

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Ching-Yi Lien ◽  
Ching-Yu Chen ◽  
Shih-Ting Lai ◽  
Chin-Feng Chan
Keyword(s):  
Kojic Acid ◽  
Lag Time ◽  
Melanoma Cells ◽  
Dependent Manner ◽  
Mushroom Tyrosinase ◽  
Inhibitory Effects ◽  
B16f10 Melanoma ◽  
B16f10 Melanoma Cells ◽  
Kinetics Of ◽  
Dose Dependent

We investigated the kinetics of 4N-acetyl-pentapeptides, Ac-P1, Ac-P2, Ac-P3, and Ac-P4, regarding inhibition of mushroom tyrosinase activity. The peptides sequences of Ac-P1, Ac-P2, Ac-P3, and Ac-P4 were Ac-RSRFK, Ac-KSRFR, Ac-KSSFR, and Ac-RSRFS, respectively. The 4N-acetyl-pentapeptides were able to reduce the oxidation ofL-DOPA by tyrosinase in a dose-dependent manner. Of the 4N-acetyl-pentapeptides, only Ac-P4 exhibited lag time (80 s) at a concentration of 0.5 mg/mL. The tyrosinase inhibitory effects of Ac-P4 (IC500.29 mg/mL) were more effective than those of Ac-P1, Ac-P2, and Ac-P3, in which IC50s were 0.75 mg/mL, 0.78 mg/mL, and 0.81 mg/mL, respectively. Kinetic analysis demonstrated that all 4N-acetyl-pentapeptides were mixed-type tyrosinase inhibitors. Furthermore, 0.1 mg/mL of Ac-P4 exhibited significant melanogenesis inhibition on B16F10 melanoma cells and was more effective than kojic acid. The melanogenesis inhibition of Ac-P4 was dose-dependent and did not induce any cytotoxicity on B16F10 melanoma cells.

scholarly journals Inhibition of plasmin by fibrinogen

1990 ◽  
Vol 269 (2) ◽  
pp. 299-302 ◽  
Author(s):  
A A R Higazi ◽  
M Mayer
Keyword(s):  
Competitive Inhibition ◽  
Hill Coefficient ◽  
Coagulation System ◽  
Amidolytic Activity ◽  
Plasmin Activity ◽  
Straight Line ◽  
Non Linear ◽  
The Hill ◽  
Kinetics Of ◽  
Kinetics Of Inhibition

The kinetics of inhibition of the amidolytic activity of plasmin on D-Val-L-Leu-L-Lys p-nitroanilide hydrochloride (S-2251) by fibrinogen and fibrin were determined. Reciprocal (1/v versus 1/[S]) plots of plasmin inhibition by 0.50 microM-fibrinogen showed a non-linear downward curve. The Hill coefficient (h) was 0.68, suggesting negative co-operativity. By contrast, fibrin produced a simple competitive inhibition of plasmin (Ki = 12 micrograms/ml). Addition of 0.1 mM-6-aminohexanoic acid shifted the non-linear curve obtained in the presence of fibrinogen to a straight line as for controls, indicating that 6-aminohexanoic acid abolishes the fibrinogen-induced inhibition. Transient exposure of the enzyme to pH 1.0 abrogates the ability of fibrinogen to inhibit plasmin activity. Acidification had no effect on the Vmax but increased the Km of plasmin. The present evidence for modulation of plasmin reveals a novel mechanism for control of fibrinolysis by fibrinogen, a component of the coagulation system and the precursor of the physiological substrate of plasmin.

scholarly journals Localization and differential induction of cytochrome P450IVA and acyl-CoA oxidase in rat liver

1991 ◽  
Vol 275 (1) ◽  
pp. 247-252 ◽  
Author(s):  
D R Bell ◽  
R G Bars ◽  
G G Gibson ◽  
C R Elcombe
Keyword(s):  
Peroxisome Proliferator ◽  
Peroxisome Proliferators ◽  
Dependent Manner ◽  
Early Markers ◽  
Acyl Coa Oxidase ◽  
Significant Change ◽  
Kinetics Of ◽  
Dose Dependent ◽  
Induced Proteins ◽  
Hepatic Cytochrome

The peroxisome proliferators are structurally diverse chemicals which induce hyperplasia, hypertrophy and the proliferation of peroxisomes in the rodent liver. Cytochrome P450IVA1 and peroxisomal enzymes, such as acyl-CoA oxidase, are induced and are early markers of treatment with peroxisome proliferators. In this study, rats were dosed intraperitoneally with the potent peroxisome proliferator methylclofenapate and the hepatic induction response was studied. There was no significant change in the enzyme activities of laurate hydroxylase (cytochrome P450IVA1) or acyl-CoA oxidase in the first 8 h after treatment, but the activities had doubled at 24 h, suggesting that these enzymes are not involved in the mediation of early events in peroxisome proliferation. Hepatic cytochrome P450IVA1 mRNA was significantly increased at 6 and 8 h after treatment, rising to 15-fold above control values at 30 h. In contrast, acyl-CoA oxidase mRNA showed no significant change in the first 8 h, but increased to 13-fold above control values at 24 and 30 h, thereby demonstrating different kinetics of induction of the two mRNAs. In order to determine whether cytochrome P450IVA1 and peroxisomal enzymes were included in the same cells, rats were treated daily with sub-maximal (2 or 5 mg/kg) and maximal (25 mg/kg) inducing doses of methylclofenapate for 4 days. The lobular distribution of induced proteins was determined immunocytochemically with antibodies raised against P450IVA1 and acyl-CoA oxidase. Livers from control animals showed minimal staining for both proteins. However, in the livers of animals treated with 2 or 5 mg of methylclofenapate/kg, both acyl-CoA and P450IVA immunostaining was increased, mainly in the centrilobular area. Immunostaining of serial sections revealed that these proteins were induced in the same region of the lobule. A maximal inducing dose of methylclofenapate (25 mg/kg) caused panlobular induction of both proteins. The results demonstrate that these proteins are induced in a dose-dependent manner in the same, spatially distinct, sensitive region of the liver lobule.

scholarly journals Pedigree analyses of yeast cells recovering from DNA damage allow assignment of lethal events to individual post-treatment generations.

Genetics ◽  
1990 ◽  
Vol 124 (1) ◽  
pp. 57-65
Author(s):  
F Klein ◽  
A Karwan ◽  
U Wintersberger
Keyword(s):  
Dna Damage ◽  
Post Treatment ◽  
Yeast Cells ◽  
Dependent Manner ◽  
The Third ◽  
Lethal Mutations ◽  
Dna Damaging Agents ◽  
Kinetics Of ◽  
Dose Dependent ◽  
Insight Into

Abstract Haploid cells of Saccharomyces cerevisiae were treated with different DNA damaging agents at various doses. A study of the progeny of individual such cells (by pedigree analyses up to the third generation) allowed the assignment of lethal events to distinct post treatment generations. By microscopically inspecting those cells which were not able to form visible colonies we could discriminate between cells dying from immediately effective lethal hits and those generating microcolonies (three to several hundred cells) probably as a consequence of lethal mutation(s). The experimentally obtained numbers of lethal events (which we call apparent lethal fixations) were mathematically transformed into mean probabilities of lethal fixations as taking place in cells of certain post treatment generations. Such analyses give detailed insight into the kinetics of lethality as a consequence of different kinds of DNA damage. For example, X-irradiated cells lost viability mainly by lethal hits (which we call 00-fixations); only at a higher dose also lethal mutations fixed in the cells that were in direct contact with the mutagen (which we call 0-fixations), but not in later generations, occurred. Ethyl methanesulfonate (EMS)-treated cells were hit by 00-fixations in a dose dependent manner; 0-fixations were not detected for any dose of EMS applied; the probability for fixation of lethal mutations was found equally high for cells of the first and second post treatment generation and, unexpectedly, was well above control in the third post-treatment generation. The distribution of all sorts of lethal fixations taken together, which occurred in the EMS-damaged cell families, was not random.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Modulation of electrical activity and ionic currents of isolated neurons by orexin A

2013 ◽  
Vol 11 (4) ◽  
pp. 54-60
Author(s):  
Petr Dmitriyevich Shabanov ◽  
Anatoliy Ivanovich Vislobokov
Keyword(s):  
Membrane Potential ◽  
Lymnaea Stagnalis ◽  
Ionic Currents ◽  
Maximal Effect ◽  
Dependent Manner ◽  
Isolated Neurons ◽  
Orexin A ◽  
High Concentrations ◽  
Kinetics Of ◽  
Dose Dependent

The changes in intracellular potential of resting (PR) and potential of action (PA) of the identified neurons of pedal and visceral ganglia of the CNS mollusk Planorbarius corneus registered by means of intracellular electrodes, and ionic currents of isolated neurons under fixed potential after administration of orexin A in concentrations 1, 10, 100 and 1000 µg/ml were studied by the method of fixation of membrane potential in isolated neurons of the Lymnaea stagnalis mollusk. Dibazol in concentrations of 1 and 10 µM effected slightly on the ionic currents. High concentrations of dibazol (100 and 1000 µM) inhibited all currents in dose dependent manner with maximal effect on potassium currents amplitude. ЕС50 were 7.4 мМ for INa, 4.0 мМ for ICa, 83.9 µM for IKs,1 (one group of neurons) and 2.9 мМ for IKs,2 (the another group of neurons). The voltage-amper membrane characteristics shift was not registered, but the kinetics of currents development was changed. Dibazol was more effective in inhibition of ionic currents compared to its structural analogs.

Retinoic Acid Inhibits CD40 + Interleukin-4–Mediated IgE Production In Vitro

Blood ◽  
1998 ◽  
Vol 92 (5) ◽  
pp. 1713-1720 ◽  
Author(s):  
M. Worm ◽  
J.M. Krah ◽  
R.A. Manz ◽  
B.M. Henz
Keyword(s):  
Retinoic Acid ◽  
B Cells ◽  
B Cell ◽  
Mononuclear Cells ◽  
Interleukin 4 ◽  
Dependent Manner ◽  
Maximal Inhibition ◽  
Ige Synthesis ◽  
Dose Dependent

Abstract To elucidate the role of retinoic acid (RA) in anti-CD40 + interleukin-4 (IL-4)–mediated B-cell activation, the effect of 10−12 to 10−6 mol/L RA was studied in anti-CD40 (1 μg/mL) + IL-4 (5 ng/mL)-mediated proliferation and Ig synthesis by human peripheral blood mononuclear cells (PBMC) and B cells in healthy donors. Anti-CD40 + IL-4–mediated proliferation of PBMC and B cells was inhibited by RA in a dose-dependent manner, with maximal inhibition of 62% ± 5% in PBMC and 55% ± 4.4% in B cells by all-trans RA, and 58% ± 6.7% and 51% ± 4.7%, respectively by 13-cis RA. IgE synthesis was even more markedly inhibited by RA starting at concentrations of >10−14mol/L for B cells and >10−10 mol/L for PBMC. Maximal inhibition of IgE production for B cells was at 10−8mol/L for all-trans RA (94% ± 1.8%) and 96% ± 3.2% for 13-cis RA. Low concentrations of RA inhibiting IgE synthesis (10−10 mol/L) affected neither B-cell proliferation nor the production of IgA, IgG, and IgM. Elucidation of the mechanism involved in this inhibition of IgE production shows that epsilon germline transcription is decreased by RA, whereas production of interferon-γ (IFN-γ) was not enhanced in the presence of RA. To differentiate whether the RA effect was mediated by RA receptors , β, and γ, the expression of the retinoic acid receptors (RAR) was examined by reverse transcriptase-polymerase chain reaction (RT-PCR). The data show that unstimulated human peripheral B cells express mRNA of the RA receptor , β, and γ. Using retinoids with different receptor binding specificity (CD336, CD437, CD2019, CD367), dose-dependent inhibition of IgE synthesis was shown by all four derivates, but was most marked by an RA binding the  receptor with high specificity. Taken together, this study shows that RA inhibits IgE production of anti-CD40 + IL-4–stimulated B cells in vitro. © 1998 by The American Society of Hematology.

scholarly journals Allosteric modulation of the activity of thrombin

1997 ◽  
Vol 321 (2) ◽  
pp. 361-365 ◽  
Author(s):  
Edward J. DUFFY ◽  
Herbert ANGLIKER ◽  
Bernard F. Le BONNIEC ◽  
Stuart R. STONE
Keyword(s):  
Active Site ◽  
Protein C ◽  
Allosteric Modulation ◽  
Anion Binding ◽  
Thrombin Receptor ◽  
Allosteric Modulator ◽  
Amidolytic Activity ◽  
Inactivation Rate Constant ◽  
Km Value ◽  
Kinetics Of

Substrates containing a P3 aspartic residue are in general cleaved poorly by thrombin. This may be partly due to an unfavourable interaction between the P3 aspartate and Glu192 in the active site of thrombin. In Protein C activation and perhaps also thrombin receptor cleavage, binding of ligands at the anion-binding exosite of thrombin seems to improve the activity of thrombin with substrates containing a P3 aspartate. To investigate the importance of Glu192 and exosite-binding in modulating thrombin's interactions with a P3 aspartate, peptidyl chloromethanes based on the sequence of the thrombin receptor (containing a P3 aspartate) have been synthesized and the kinetics of their inactivation of α-thrombin and the mutant Glu192 → Gln determined. The values of the inactivation rate constant (ki) for the chloromethanes containing a P3 aspartate were about two-fold higher with the Glu192 → Gln mutant. A peptide based on the sequence of hirudin (rhir52Ő65), which binds to the anion-binding exosite of thrombin, was an allosteric modulator of the amidolytic activity of the Glu192 → Gln mutant; a 5-fold decrease in the Km value for the substrate d-Phe-pipecolyl-Arg-p-nitroanilide was observed in the presence of saturating concentrations of rhir52Ő65. This exosite-binding peptide also increased the ki values of chloromethanes containing a P3 aspartate with both α-thrombin and the Glu192 → Gln mutant. However, the increases in the ki values were greater with the Glu192 → Gln mutant (5-fold compared with 2-fold for α-thrombin). Thus exosite binding does not seem to mitigate putative unfavourable interactions between Glu192 and the P3 aspartate. Moreover, increases in the ki caused by exosite binding were not unique to chloromethanes containing a P3 aspartate; increases of the same magnitude were also observed when the P3 position was occupied by the favourable d-phenylalanine in place of the unfavourable aspartate. The results obtained were consistent with exosite binding's causing changes in the conformation of the S2 and/or S1 sites of thrombin.

scholarly journals THE MOLLUSC IONIC CURRENTS CHANGES AFTER ADMINISTRATION OF N-PHENYLALKYL DERIVATIVES OF TAURINE

2012 ◽  
Vol 10 (4) ◽  
pp. 67-72
Author(s):  
Anatoliy Ivanovich Vislobokov ◽  
Lyudmila Konstantinovna Khnychenko ◽  
Yuriy Dmitriyevich Ignatov ◽  
Nikolay Sergeyevich Sapronov ◽  
Petr Dmitriyevich Shabanov
Keyword(s):  
Lymnaea Stagnalis ◽  
Ionic Currents ◽  
Ionic Channels ◽  
Dependent Manner ◽  
Isolated Neurons ◽  
Sodium Potassium ◽  
Fixed Membrane ◽  
Kinetics Of ◽  
Dose Dependent ◽  
Derivatives Of

The transmembrane sodium, potassium and calcium ionic currents were studied after extracellular administration of N-phenylalkyl derivatives of taurine in concentrations 1, 10, 100 and 1000 mM. The method of intracellular dialysis with fixed membrane potential was used in model of isolated neurons of the mollusks Lymnaea stagnalis and Planorbarius corneus. The solutions containing 1 and 10 mM of the compounds studied did not change ionic channels activity in isolated neurons. Concentrations 100 and mM depressed reversibly all currents in the dose-dependent manner: taurine < TAU-02 < TAY-15 < TAU-60. The voltage-amplitude membrane characteristics as well as kinetics of the currents did not change.

The kinetics of exsheathment of infective nematode larvae is disturbed in the presence of a tannin-rich plant extract (sainfoin) both in vitro and in vivo

Parasitology ◽  
2007 ◽  
Vol 134 (9) ◽  
pp. 1253-1262 ◽  
Author(s):  
S. BRUNET ◽  
J. AUFRERE ◽  
F. El BABILI ◽  
I. FOURASTE ◽  
H. HOSTE
Keyword(s):  
Parasite Species ◽  
Gastrointestinal Nematodes ◽  
Dependent Manner ◽  
Early Step ◽  
Nematode Larvae ◽  
Kinetics Of ◽  
Dose Dependent

SUMMARYThe mode of action of bioactive plants on gastrointestinal nematodes remains obscure. Previous in vitro studies showed that exsheathment was significantly disturbed after contact with tannin-rich extracts. However, the role of important factors (extract concentration, parasite species) has not been assessed and no information is available on the occurrence in vivo. These questions represent the objectives of this study. The model incorporated the parasites Haemonchus contortus and Trichostrongylus colubriformis with sainfoin as the bioactive plant. A set of in vitro assays was performed, measuring the changes observed, after 3 h of contact with increasing concentrations of sainfoin, on the rate of artificial exsheathment. The results indicated that sainfoin extracts interfered with exsheathment in a dose-dependent manner and the process overall was similar for both nematodes. The restoration of control values observed after adding PEG to extracts confirms a major role for tannins. A second study was performed in vivo on rumen-cannulated sheep fed with different proportions of sainfoin in the diet to verify these in vitro results. The consumption of a higher proportion of sainfoin was indeed associated with significant delays in Haemonchus exsheathment. Overall, the results confirmed that interference with the early step of nematode infection might be one of the modes of action that contributes to the anthelmintic properties of tanniniferous plants.

5,5'-Diphenylhydantoin decreases the entry of 3,5,3'-triiodo-L-thyronine but not L-thyroxine in cultured GH-producing cells

1988 ◽  
Vol 117 (3) ◽  
pp. 392-398 ◽  
Author(s):  
Leonard R. Zemel ◽  
David R. Biezunski ◽  
Lawrence E. Shapiro ◽  
Martin I. Surks
Keyword(s):  
Plasma Membrane ◽  
Thyroid Hormone ◽  
Dependent Manner ◽  
Exit Rate ◽  
Entry And Exit ◽  
Serum Free ◽  
Fractional Rate ◽  
Serum Free Conditions ◽  
Kinetics Of ◽  
Dose Dependent

Abstract. We determined the effect of 5,5'-diphenylhydantoin (DPH) on the kinetics of T3 and T4 uptake in cultured GH-producing (GC) cells under serum-free conditions. GC cells accumulated [125I]T3 at a greater fractional rate than [125I]T4. The t½ of exit of [125I]T4 and [125I]T3 previously equilibrated in GC cells was 28 min for T4 and 66 min for T3. T3 and T4 entry rates were not influenced by up to a 10 000-fold molar excess of nonradioactive T3, T4, d-T4, rT3, 3,5-T2 and diiodotyrosine. Thus, entry of T3 and T4 in GC cells appeared nonsaturable and was not influenced by various thyroid hormone analogues. DPH, 25–200 μmol/l, decreased the rate of T3 entry in a dose-dependent manner and did not influence the T3 exit rate. At 200 μmol/l DPH, T3 entry decreased by 40%. Rates of entry and exit of T4 were unaffected by DPH. DPH may affect T3 and T4 entry differentially at the level of the plasma membrane.

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