PHYSIOLOGY OF SELENITE REDUCTION BY ENTEROCOCCI: II. CHARACTERIZATION OF SELENITE INHIBITION AND ITS REVERSAL BY ASCORBATE

1967 ◽  
Vol 13 (9) ◽  
pp. 1183-1193 ◽  
Author(s):  
Richard C. Tilton ◽  
Haim B. Gunner ◽  
Warren Litsky
Keyword(s):  
Active Site ◽  
Flavin Adenine Dinucleotide ◽  
Inhibitory Effect ◽  
Inhibitory Effects ◽  
Selenite Reduction ◽  
Heat Stable ◽  
Oxygen Sensitive ◽  
Test Organisms ◽  
Reduced Nicotinamide Adenine Dinucleotide

Cell-free extracts of Streptococcus faecalis N83 and Streptococcus faecium K6A were shown to possess comparable enzyme systems for the reduction of selenite to metallic selenium. The enzymatic complement of each of the organisms was oxygen sensitive, heat stable, and required flavin adenine dinucleotide (FAD) for maximum stimulation. Potent reduced nicotinamide adenine dinucleotide (NADH2) oxidase activity was demonstrated in extracts of both organisms. Although the NADH2 oxidase of S. faecium was sensitive to sulfhydryl inhibitors, the enzyme in S. faecalis was unaffected. The addition of ascorbate to the medium reversed the inhibitory effects of selenite and enhanced selenite reduction by S. faecium. Radioisotope studies, utilizing selenium75, demonstrated that selenite was taken up by both test organisms. The addition of ascorbate increased the rate and extent of selenium75 incorporation. It was concluded that the inhibitory effect of selenite and the inability of S. faecium to reduce the ion is a reflection of the oxidation by selenite of sulfhydryl groups on the active site.

scholarly journals DIFFERENTIAL INHIBITORY EFFECTS OF CHOLERA TOXOIDS AND GANGLIOSIDE ON THE ENTEROTOXINS OF VIBRIO CHOLERAE AND ESCHERICHIA COLI

1973 ◽  
Vol 137 (4) ◽  
pp. 1009-1023 ◽  
Author(s):  
Nathaniel F. Pierce
Keyword(s):  
Escherichia Coli ◽  
Binding Sites ◽  
Competitive Inhibitor ◽  
Inhibitory Effect ◽  
Inhibitory Effects ◽  
E Coli ◽  
Stable Component ◽  
Heat Stable ◽  
Cholera Enterotoxin ◽  
Gut Mucosa

Natural cholera toxoid appears to act as a competitive inhibitor of cholera enterotoxin and is thus a useful tool for studying the interaction of cholera enterotoxin with cell membranes. Cholera enterotoxin binds to gut mucosa more rapidly than does its natural toxoid. Once binding occurs, however, it appears to be prolonged for both materials. Formalinized cholera toxoid has no inhibitory effect upon cholera enterotoxin. Enterotoxic activity, ability to bind to gut mucosa, and antitoxigenicity appear to be independent properties of cholera enterotoxin. Natural cholera toxoid does not inhibit Escherichia coli enterotoxin, indicating that although the two enterotoxins activate the same mucosal secretory mechanism they occupy different binding sites in the mucosa. Ganglioside, which may be the mucosal receptor of cholera enterotoxin, is highly efficient in deactivating cholera enterotoxin. By contrast, ganglioside is relatively inefficient in deactivating heat-labile E. coli enterotoxin and is without effect upon the heat-stable component of E. coli enterotoxin. These findings suggest that ganglioside is not likely to be the mucosal receptor for E. coli enterotoxin. Differences in cellular binding of E. coli and cholera enterotoxins may explain, at least in part, the marked differences in the time of onset and duration of their effects upon gut secretion.

scholarly journals 86Rb is not a reliable tracer for potassium in skeletal muscle

1994 ◽  
Vol 302 (3) ◽  
pp. 745-751 ◽  
Author(s):  
I Dørup ◽  
T Clausen
Keyword(s):  
Skeletal Muscle ◽  
Soleus Muscle ◽  
Inhibitory Effect ◽  
Transport Processes ◽  
Inhibitory Effects ◽  
Rat Erythrocytes ◽  
Calcitonin Gene ◽  
Rat Soleus Muscle ◽  
K Transport

For technical reasons, 86Rb is frequently preferred to 42K as a tracer for K+. Systematic comparisons of the two isotopes, however, are rarely done. In this paper we compare the transport of 42K and 86Rb in rat and mouse soleus muscle and in rat erythrocytes. Ouabain-suppressible K+ uptake in rat soleus was the same whether measured with 42K or 86Rb, both when stimulated by insulin, salbutamol and calcitonin-gene-related peptide (CGRP), and when inhibited by graded concentrations of ouabain. Control experiments with rat erythrocytes, where Na(+)-K(+)-Cl- co-transport has earlier been demonstrated, showed closely similar inhibitory effects of bumetanide on 42K and 86Rb uptake. In contrast, bumetanide produced no significant change in 42K uptake of rat and mouse soleus muscle, but clearly inhibited 86Rb uptake at concentrations down to 10(-7) M (P < 0.001). Whereas the addition of 150 mM NaCl had no effect on 42K uptake in rat soleus, 86Rb uptake, and in particular the bumetanide-suppressible component, was markedly increased by this addition. The inhibitory effect of bumetanide on 86Rb uptake gives rise to the false impression that skeletal muscle contains a NaKCl2 co-transport system. Efflux studies showed that the fractional loss of 42K from rat soleus muscle is 2.3 times larger than that of 86Rb. Salbutamol and CGRP increased 86Rb efflux, but inhibited 42K efflux. This implies that for studies of K+ efflux and bumetanide-sensitive K+ transport, 86Rb is not even an acceptable tracer for the detection of qualitative changes. Control experiments with 42K are essential in any characterization of unknown K+ transport processes.

Inhibitory effects of luteolin and its derivatives on osteoclast differentiation and differences in luteolin production by Capsicum annuum varieties

2021 ◽  
Author(s):  
Shintaro Onishi ◽  
Shinichi Tebayashi ◽  
Yasufumi Hikichi ◽  
Hiromasa Sawada ◽  
Yukiko Ishii ◽  
...  
Keyword(s):  
Capsicum Annuum ◽  
Osteoclast Differentiation ◽  
Inhibitory Effect ◽  
Plant Residue ◽  
Plant Residues ◽  
Inhibitory Effects ◽  
Effective Development ◽  
Osteoclastic Differentiation ◽  
Identification And Characterization

ABSTRACT Luteolin, an abundant flavonoid in the leaves of Capsicum annuum, has antioxidant activity and is, thus, a key chemical for promoting plant residue utilization, especially for the development of healthcare products. We assessed the inhibitory effect of luteolin and its glycosides on osteoclastic differentiation in human cells and found that the differentiation was effectively inhibited at noncytotoxic concentrations. We also screened 47 varieties of C. annuum for the accumulation of luteolin and apigenin to determine the prevalence of luteolin in diverse cultivars and identify varieties with high and/or selective luteolin production. The glycosides of luteolin and apigenin were found in all the tested varieties, with luteolin predominant over apigenin in most varieties. The identification and characterization of highly productive varieties of C. annuum is expected to be beneficial for the effective development of useful luteolin-based products from plant residues.

Isolation and characterization of chemical constituents from Chaerophyllum bulbosum roots and their enzyme inhibitory and antioxidant effects

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Gülsen Tel-Çayan ◽  
Ebru Deveci ◽  
Zeynep Molo ◽  
Mehmet Emin Duru ◽  
Mehmet Öztürk
Keyword(s):  
Chemical Constituents ◽  
Inhibitory Effect ◽  
Therapeutic Agents ◽  
Inhibitory Effects ◽  
Root Extracts ◽  
Isolation And Characterization ◽  
Therapeutic Uses ◽  
Antioxidant Effects ◽  
Novel Therapeutic

Abstract Isolation and bioactive effects of the roots of Chaerophyllum bulbosum L. were firstly investigated herein. Enzyme (acetylcholinesterase, butyrylcholinesterase, urease, α-amylase, α-glucosidase, and tyrosinase) inhibitory effects of C. bulbosum root extracts were tested. Three known compounds, n-heptadecanyl eicosanoate (1), stigmasterol (2), and β-sitosterol-3-O-β-d-glucopyranoside (3) were isolated from C. bulbosum. Antioxidant and enzyme inhibitory effects of isolated compounds were investigated. The hexane extract (IC50: 349.58 ± 0.06 μg/mL) displayed a higher α-glucosidase inhibitory effect than the standard (IC50: 378.66 ± 0.14 μg/mL). The best inhibitory effect was found in compound 2 on AChE (46.40 ± 0.31%), BChE (56.41 ± 0.54%), and urease (92.47 ± 0.11%); compound 1 on α-amylase (22.27 ± 0.61%); and compound 3 on α-glucosidase (12.43 ± 0.25%) and tyrosinase (19.00 ± 0.16%). All isolated compounds showed moderate antioxidant effects in all assays. This study contributes to the therapeutic uses of Chaerophyllum roots and emphasizes the value of C. bulbosum species for the development of novel therapeutic agents.

scholarly journals Characterization of the first non-insect invertebrate functional angiotensin-converting enzyme (ACE): leech TtACE resembles the N-domain of mammalian ACE

2004 ◽  
Vol 382 (2) ◽  
pp. 565-573 ◽  
Author(s):  
Guillaume RIVIÈRE ◽  
Annie MICHAUD ◽  
Laurence DELOFFRE ◽  
Franck VANDENBULCKE ◽  
Angélique LEVOYE ◽  
...  
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Active Site ◽  
Active Sites ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Inhibitory Effect ◽  
Converting Enzyme ◽  
Ovary Cells

Angiotensin-converting enzyme (ACE) is a zinc metallopeptidase that plays a major role in blood homoeostasis and reproduction in mammals. In vertebrates, both transmembrane and soluble ACE, containing one or two homologous active sites, have been characterized. So far, several ACEs from invertebrates have been cloned, but only in insects. They are soluble and display a single active site. Using biochemical procedures, an ACE-like activity was detected in our model, the leech, Theromyzon tessulatum. Annelida is the most distant phylum in which an ACE activity has been observed. To gain more insight into the leech enzyme, we have developed a PCR approach to characterize its mRNA. The approx. 2 kb cDNA has been predicted to encode a 616-amino-acid soluble enzyme containing a single active site, named TtACE (T. tessulatum ACE). Surprisingly, its primary sequence shows greater similarity to vertebrates than to invertebrates. Stable in vitro expression of TtACE in transfected Chinese-hamster ovary cells revealed that the leech enzyme is a functional metalloprotease. As in mammals, this 79 kDa glycosylated enzyme functions as a dipeptidyl carboxypeptidase capable of hydrolysing angiotensin I to angiotensin II. However, a weak chloride inhibitory effect and acetylated N-acetyl-SDKP (Ac SDAcKP) hydrolysis reveal that TtACE activity resembles that of the N-domain of mammalian ACE. In situ hybridization shows that its cellular distribution is restricted to epithelial midgut cells. Although the precise roles and endogenous substrates of TtACE remain to be identified, characterization of this ancestral peptidase will help to clarify its physiological roles in non-insect invertebrate species.

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.

Characterization of Thromboxane A2/Prostaglandin H2 Receptors in Porcine Coronary Artery -The Inhibitory Effect of a Novel Dibenzoxepin Derivative, KW-3635

1992 ◽  
Vol 67 (05) ◽  
pp. 582-584 ◽  
Author(s):  
Ichiro Miki ◽  
Akio Ishii
Keyword(s):  
Coronary Artery ◽  
Binding Sites ◽  
Thromboxane A2 ◽  
Inhibitory Effect ◽  
Scatchard Analysis ◽  
Single Class ◽  
Porcine Coronary Artery ◽  
Equilibrium Binding ◽  
H2 Receptors

SummaryWe characterized the thromboxane A2/prostaglandin H2 receptors in porcine coronary artery. The binding of [3H]SQ 29,548, a thromboxane A2 antagonist, to coronary arterial membranes was saturable and displaceable. Scatchard analysis of equilibrium binding showed a single class of high affinity binding sites with a dissociation constant of 18.5 ±1.0 nM and the maximum binding of 80.7 ± 5.2 fmol/mg protein. [3H]SQ 29,548 binding was concentration-dependently inhibited by thromboxane A2 antagonists such as SQ 29,548, BM13505 and BM13177 or the thromboxane A2 agonists such as U46619 and U44069. KW-3635, a novel dibenzoxepin derivative, concentration-dependently inhibited the [3H]SQ 29,548 binding to thromboxane A2/prosta-glandin H2 receptors in coronary artery with an inhibition constant of 6.0 ± 0.69 nM (mean ± S.E.M.).

Characterization of an Abnormal Antithrombin (Milano 2) with Defective Thrombin Binding

1986 ◽  
Vol 56 (03) ◽  
pp. 349-352 ◽  
Author(s):  
A Tripodi ◽  
A Krachmalnicoff ◽  
P M Mannucci
Keyword(s):  
Venous Thromboembolism ◽  
Active Site ◽  
Inhibitory Activity ◽  
Antithrombin Iii ◽  
Factor Xa ◽  
Molecular Defect ◽  
Affinity Adsorption ◽  
Italian Family ◽  
Crossed Immunoelectrophoresis

SummaryFour members of an Italian family (two with histories of venous thromboembolism) had a qualitative defect of antithrombin III reflected by normal antigen concentrations and halfnormal antithrombin activity with or without heparin. Anti-factor Xa activities were consistently borderline low (about 70% of normal). For the propositus’ plasma and serum the patterns of antithrombin III in crossed-immunoelectrophoresis with or without heparin were indistinguishable from those of normal plasma or serum. A normal affinity of antithrombin III for heparin was documented by heparin-sepharose chromatography. Affinity adsorption of the propositus’ plasma to human α-thrombin immobilized on sepharose beads revealed defective binding of the anti thrombin III to thrombin-sepharose. Hence the molecular defect of this variant appears to be at the active site responsible for binding and neutralizing thrombin, thus accounting for the low thrombin inhibitory activity.

Inhibition of ADP-Induced Responses in Human Platelets by Agents Elevating the Cyclic AMP Level: Comparison of Aggregation and Shape Change

1984 ◽  
Vol 52 (03) ◽  
pp. 333-335 ◽  
Author(s):  
Vider M Steen ◽  
Holm Holmsen
Keyword(s):  
Inhibitory Action ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Shape Change ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Inhibitory Effects ◽  
Early Step ◽  
Stimulus Response ◽  
Sequential Relationship

SummaryThe inhibitory effect of cAMP-elevating agents on shape change and aggregation in human platelets was studied to improve the understanding of the sequential relationship between these two responses.Human platelet-rich plasma was preincubated for 2 min at 37° C with prostaglandin E1 or adenosine, agents known to elevate the intracellular level of cAMP. Their inhibitory effects on ADP-induced shape change and aggregation were determined both separately and simultaneously. The dose-inhibition patterns for shape change and aggregation were similar for both PGE1 and adenosine. There was no distinct difference between the inhibitory action of these two inhibitors.These observations suggest that elevation of the intracellular concentration of cAMP interferes with an early step in the stimulus-response coupling that is common for aggregation and shape change.

Sign in / Sign up

Export Citation Format

Share Document