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PubMed1983

Ribosomal subunits and ribosomal proteins of Tetrahymena thermophila. Effect of the presence of iodoacetamide during ribosome extraction on the properties of the subunits.

Proteolytic degradation of ribosomal proteins occurs during the preparation of subunits of the cytoplasmic ribosomes of the protozoa Tetrahymena thermophila and the isolated subunits are inactive. Addition of 5 mM iodoacetamide to cell suspensions before extraction inhibits proteolytic activity and permits isolation of active subunits. The protein complements of these subunits have been characterized in two different two-dimensional electrophoretic systems, and their molecular weights have been determined.

Animals↗
PubMed1975

Sequential morphological changes of ulceration in the glandular stomach of rats induced by iodoacetamide.

Two groups of 25 male Wistar rats were given 0.1% iodoacetamide (IAM) with or without 0.4% Tween 60 in their drinking water for 12 weeks. Two or three rats from each group were sacrificed at intervals for sequential morphological observations on ulceration of gastric mucosa. The ulcers invariably developed in the fundic region adjacent to the limiting ridge, and they penetrated the muscle coats and extended to the serosal lining on continuous treatment with IAM for 9 weeks. The ulcers appeared chronic, but when IAM was discontinued the healing process began rapidly and the mucosa regenerated almost completely within six weeks. Regenerating epithelium on areas of ulcer differentiated progressively, and the renewed mucosa showed pyloric metaplasia.

Animals↗
PubMed1985

Marked epithelial hyperplasia of the rat glandular stomach induced by long-term administration of iodoacetamide.

Iodoacetamide (IAA), an ulcerogenic compound, was continuously given to male Wistar rats for up to 74 weeks. No carcinomas developed but marked glandular hyperplasias were frequently observed accompanied by chronic ulcer or erosion in the fundic region. They showed pseudo-invasive growth into the submucosa, the granulomatous tissue and even into the muscle layer, but no cellular and nuclear atypia was observed in their glands. Characteristically the mucosal damage caused by chronic IAA treatment was restricted to the fundic mucosa along the limiting ridge. Abnormally regenerated mucosa in the damaged area showed pyloric gland type metaplasia, demonstrated histochemically by paradoxical concanavalin A-staining and high-iron diamine-Alcian blue staining for mucin. No intestinal metaplasia was observed in these mucosa.

Animals↗
PubMed1993

Characterization of skeletal muscle actin labeled with the triplet probe erythrosin-5-iodoacetamide.

We have labeled rabbit skeletal muscle actin with the triplet probe erythrosin-5-iodoacetamide and characterized the labeled protein. Labeling decreased the critical concentration and lowered the intrinsic viscosity of F-actin filaments; labeled filaments were motile in an in vitro motility assay but were less effective than unlabeled F-actin in activating myosin S1 ATPase activity. In unpolymerized globular actin (G-actin), both the prompt and delayed luminescence were red-shifted from the spectra of the free dye in solution and the fluorescence anisotropy of the label was high (0.356); filament formation red shifted all excitation and emission spectra and increased the fluorescence anisotropy to 0.370. The erythrosin phosphorescence decay was at least biexponential in G-actin with an average lifetime of 99 microseconds while in F-actin the decay was approximately monoexponential with a lifetime of 278 microseconds. These results suggest that the erythrosin dye was bound at the interface between two actin monomers along the two-start helix. The steady-state phosphorescence anisotropy of F-actin was 0.087 at 20 degrees C and the anisotropy increased to approximately 0.16 in immobilized filaments. The phosphorescence anisotropy was also sensitive to binding the physiological ligands phalloidin, cytochalasin B and tropomyosin. This study lays a firm foundation for the use of this triplet probe to study the large-scale molecular dynamics of F-actin.

Actins↗
PubMed1979

Non-competitive-non-equilibrium alpha-adrenoceptor blocking properties of N-benzyl iodoacetamide, betsamide.

N-Benzyl iodoacetamide, betsamide, at 10 mg kg-1 i.v. blocked the hypertensive and contractile responses of the nictitating membrane of the cat to adrenaline. The blockade had a lag period before full development. Pretreatment of cats with betsamide for 7 or 18 h showed a non-equilibrium type of alpha-adrenoceptor blockade. The responses of the nictitating membrane to adrenaline were markedly depressed and did not recover after high doses of adrenaline. In the same cats, adrenaline caused a profound hypotension. The effect of betsamide lasted for at least 72 h. In the rat isolated vas deferens, 3 X 10(-5) M betsamide non-competitively blocked the contractile responses to noradrenaline; the adrenoceptor blockade was less effective when betsamide was applied with noradrenaline. The blockade lasted for more than 24 h, and was not reversible after extensive washing. Betsamide antagonized the contractile effects of carbachol and 5-hydroxytryptamine on the rat vas deferens, but not the beta-responses of the guinea-pig trachea to adrenaline and isoproenaline. Results are discussed in relation to a probable mechanism of action.

Adrenergic alpha-Antagonists↗
PubMed1992

Monomer and excimer fluorescence of horse plasma gelsolin labelled with N-(1-pyrenyl)iodoacetamide.

Horse plasma gelsolin was labelled with the sulfhydryl-specific fluorescent reagent N-(1-pyrenyl)iodoacetamide. The level of incorporation of probe was 1.6 +/- 0.3 mol pyrene/mol gelsolin. The circular dichroism spectrum of pyrenyl-gelsolin and its ability to interact with muscle actin were not different from that found for unmodified gelsolin. The emission from pyrenyl-gelsolin was dominated by a broad emission band centred near 483 nm, characteristic of the presence of pyrene excimers. Analysis of excitation spectra for the monomer and excimer-type fluorescence suggested that ground-state interactions may occur between adjacent pyrenes in the gelsolin structure. In the case either of excimer formation or of ground-state pyrene-pyrene interactions in doubly labelled gelsolin molecules, the modified Cys residues must be in close proximity in the folded protein structure. Thermal denaturation of gelsolin could be monitored by observing the decrease in excimer emission that accompanied heating and unfolding of the tertiary structure. While heat treatment alone did not eliminate excimer fluorescence, digestion of gelsolin with chymotrypsin completely abolished such emission. Also, pyrenyl-gelsolin prepared and studied in 6 M guanidine-HCl exhibited fluorescence characteristic of pyrene monomers exclusively.

Actins↗
PubMed2006

Morphological and biochemical alterations in the jejunum following iodoacetamide-induced colitis in rats.

This study aims to describe the morphological alterations in the small and large intestines as well as the expression of some enterocyte enzymes and carriers in a rat model of iodoacetamide-induced colitis. Biopsies from the large and small intestines were taken at 1, 2, 4, 8, and 16 days postinduction and studied by light microscopy. The expressions of lactase, sucrase, aminopeptidase, and Glut-5 in the jejunum were studied by immunohistochemistry. Gene expressions of enterocyte lactase and sucrase were determined by RT-PCR using specific oligonucleotides. Microscopic examination of the large intestines revealed manifestations concordant with inflammation. Such alterations peaked at 2 days, were maintained to a lesser extent for 4 days, regressed by 8 days, and healed by 16 days. In the jejunum, the expression of lactase, sucrase, and aminopeptidase decreased 2 days after colitis induction, and recovered 2 days later. Similarly, Glut-5 expression decreased transiently with partial recovery by day 8. Compared with sham, gene expression of jejunal brush border enzymes sucrase and lactase showed a 4-fold increase in lactase and a 9-fold increase in sucrase after 4 days. We conclude that colitis can induce significant functional abnormalities in distant noninflamed small bowel regions.

Aminopeptidases↗
PubMed1997

Cytotoxicity of naphthoquinones toward cultured resting murine leukemia L1210 cells in the presence of glutathione, diethyl maleate, or iodoacetamide.

Sixteen naphthoquinones with various substituents were tested for cytotoxicity toward cultured resting leukemia L1210 cells. The cytotoxicity of all the naphthoquinones examined was not affected at all by the treatment in combination with diethyl maleate, a glutathione-specific SH-blocking agent in the cells. Depending on the characteristics of the response to the treatment in combination with iodoacetamide (IAA) and glutathione (GSH), these naphthoquinones were tentatively classified into three groups. The chemicals of Group I, which include naphthoquinones carrying an electron-donating group(s) other than an OH group on the quinone ring moiety, showed synergistic cytotoxicity with IAA and no reduction in cytotoxicity with GSH. Those of Group II, which include naphthoquinones without an electron-donating group on the quinone ring moiety, showed no synergy with IAA but appreciable reductions in cytotoxicity with GSH. Group III includes 2-hydroxylated naphthoquinones, which showed neither synergy with IAA nor cytotoxicity reduction with GSH. Cytotoxicity was discussed in terms of the electron-deficiency of the quinone ring moiety. It is suggested that the cytotoxicity of Group I quinones comes from the active oxygen generation which follows semiquinone formation, whereas that of the other groups of quinones is not likely caused simply by either SH-blocking of biomolecules or active oxygen-related mechanism.

Alkylating Agents↗
PubMed1977

The effect of iodoacetamide-induced fundic ulcers on gastric carcinogenesis produced by N-methyl-N'-nitro-N-nitrosoguanidine in rats.

This study was undertaken to determine the effect of ulcer induced by iodoacetamide on the development of gastric carcinoma by N-methyl-N'-nitro-N-nitrosoguanidine in male Wistar rats. Fifty-six of the 62 ulcers induced by IAM were located in the fundic gland area along the limiting ridge. The incidence of fundic carcinoma was 16% in the groups treated with IAM and MNNG, while no fundic carcinoma was found in the group treated with MNNG alone. This difference was statistically significant. All the carcinomas in the fundic gland area were confined within the ulcer itself or its scar tissue, produced by IAM. These findings indicate that if an ulcer is present, carcinoma develops even in the fundic mucosa which is, if intact, resistant to the carcinogenic stimulation of MNNG. It was concluded that gastric ulcer predisposes the development of gastric carcinoma.

Adenocarcinoma↗
PubMed1992

[Metabolic and functional consequences of complete inhibition of creatine kinase by iodoacetamide in the perfused heart].

Treatment of perfused rat hearts with 0.5 mM iodoacetamide (IAAm) for 15 min at different workloads resulting in a nearly complete inhibition of creatine kinase (CK, 99%) was followed by a rapid decline of the phosphocreatine (PCr) level (30%) and a 2-fold increase of the P(i) level which then stabilized. Conversely, the ATP content started to drop monotonously at the beginning of the IAAm washout and reached 30% 90 min after the IAAm removal under medium load. Under low workload the ATP decay occurred at later periods. Neither the ADP-stimulated mitochondrial respiration in skinned fibers, nor the Ca(2+)-stimulated ATPase activity of myofibrils was affected by IAAm treatment. The sensitivity of the resting tension of skinned fibers to Ca2+ tended to a slight increase. The cardiac work index (PRP-pressure-rate product) decreased by 25%, while the end diastolic pressure (EDP) rose by 15 mm Hg when IAAm acted under medium load. In contrast, under low work these parameters were practically stable. The hearts poisoned with IAAm performed a two times lower maximal work and had reduced (by 35%) oxygen consumption rates. The efficiency of energy utilization for mechanical work decreased by 40%. The changes in PRP and EDP correlated with the cytosolic [ATP]/[ADP] ratio in such a way that the decrease in the latter was associated with a decrease in PRP and the elevation of EDP. These data suggest that the creatine kinase system is necessary for the effective translation of a high [ATP]/[ADP] ratio from the intermembrane space of mitochondria to the cytoplasm, myofibrils and ionic pumps. This provides a high level of mechanical work and good relaxation of the left ventricle and protects cytosolic adenine nucleotides from the breakdown.

Adenine Nucleotides↗
PubMed1989

Studies on the catalytic site of rat liver HMG-CoA reductase: interaction with CoA-thioesters and inactivation by iodoacetamide.

The localization of reactive cysteines and characterization of the HMG-CoA binding domain of rat liver HMG-CoA reductase were studied using iodoacetamide (IAAD) and short-chain acyl-CoA thioesters. Freeze-thaw-solubilized HMG-CoA reductase is irreversibly inactivated by IAAD with a second order rate constant of 0.78 M-1 sec-1 at 37 degrees C and pH 7.2. This IAAD inactivation is slowed down by pretreatment of the enzyme with disulfides, indicating that inactivation of HMG-CoA reductase occurs mainly through alkylation of specific cysteine residues in the protein. The substrate HMG-CoA, but not NADP(H), effectively protects the reductase from IAAD inactivation. When both HMG-CoA and NADP(H) are present, the reductase is inactivated by IAAD at a rate much faster than the inactivation in the presence of HMG-CoA alone. Of the two moieties of the HMG-CoA thioester, the CoA moiety confers protection from IAAD inactivation whereas HMG is totally ineffective. A series of CoA-thioesters of mono- and dicarboxylic acids of various size were tested for their effect on the activity of HMG-CoA reductase. The CoA analog, desulfo-CoA (des-CoA), and all CoA-thioesters of monocarboxylic acids of up to 6 carbons in length exhibit mixed-type inhibition of reductase activity. The competitive inhibition constants (Ki) for these compounds vary between 1 and 2 mM, whereas the noncompetitive component (K'i) is relatively constant (540 +/- 20 microM). As the acyl chain length increases beyond 6 carbons, the thioesters of monocarboxylic acids become more potent and acquire the characteristics of pure noncompetitive inhibitors. In contrast, the monothioesters of dicarboxylic acids are pure competitive inhibitors with Ki values which are similar to the Ki values of the corresponding thioesters of monocarboxylates. HMG does not affect reductase activity in concentrations of up to 2 mM, yet it greatly enhances the inhibition of the enzyme by des-CoA. Specifically, HMG affects only the Ki value of des-CoA by decreasing it from 1030 microM to 280 microM. The results indicate that reactive cysteine(s) are localized in the catalytic site of HMG-CoA reductase. Within the active site, these cysteines are closely associated with and probably participate in the binding of the CoA moiety of the substrate HMG-CoA. The results are also consistent with the existence of a noncatalytic hydrophobic site in HMG-CoA reductase.

Acyl Coenzyme A↗
PubMed1985

The effects of colchicine analogues on the reaction of tubulin with iodo[14C]acetamide and N,N'-ethylenebis(iodoacetamide).

We have previously found (Ludueña, R. F., and Roach, M. C. (1981b) Biochemistry 20, 4444-4450) that colchicine and podophyllotoxin inhibit the alkylation of tubulin by iodo[14C]acetamide and the formation of an intrachain cross-link in the beta-tubulin subunit by N,N'-ethylenebis(iodoacetamide) (EBI). It was not clear whether these effects were due to conformational changes in tubulin induced by drugs or to direct steric blockage of the sulfhydryl groups involved. In an effort to characterize further these phenomena, we have examined the effects of single-ring and bicyclic analogues of colchicine on the reaction of tubulin with iodo[14C]acetamide and EBI. We have found that neither the A-ring analogues, 3,4,5-trimethoxybenzyl alcohol, 3,4,5-trimethoxybenzaldehyde, 2,3,4-trimethoxybenzaldehyde, and benzaldehyde, nor the C-ring analogues, tropolone and tropolone methyl ether, inhibited alkylation. In contrast, colchicine, podophyllotoxin, and nocodazole and the bicyclic analogues, 5-(2',3',4'-trimethoxyphenyl)-2-methoxytropone and combretastatin, inhibited tubulin alkylation. Since the presence of a bond joining the A and C rings seems to be the determining factor in the suppression of alkylation, it is likely that inhibition by colchicine of the reaction with iodo[14C] acetamide is due largely to a conformational change induced by colchicine. A different pattern was obtained when the effects on cross-link formation by EBI were examined. Here, all the A-ring analogues, the bicyclic analogues, and colchicine, podophyllotoxin, and nocodazole all inhibited formation of the cross-link, whereas the C-ring analogue tropolone methyl ether did not inhibit cross-link formation. Since compounds whose effect on alkylation is markedly different have the same effect on cross-link formation, it is possible that this effect is a steric one and that perhaps the A-ring of colchicine binds to tubulin very close to one of the sulfhydryls involved in the intrachain cross-link formed by EBI in beta-tubulin.

Alkylation↗
PubMed1981

Cyclic AMP-dependent protein kinase activity and lipolysis in adipose tissue. Effect of fasting, oligomycin and iodoacetamide.

The release of glycerol into the medium, the concentration of cAMP, and the cAMP-dependent protein-kinase activity were studied in adipocytes and in fat-pads obtained from epididymal adipose tissue of rats under different conditions of feeding. An increase in the tissue concentration of cAMP and in the protein-kinase activity was observed in vivo at 48 and 96 h of fasting. A diminished release of glycerol was found in adipocytes from rats fasted for 48 h, in the absence of glucose, and the maximum concentration of cAMP was inferior to that of fed rats. Oligomycin and iodoacetamide, in the presence of epinephrine and glucose, produce a diminution in the values of the parameters studied. No significant differences were observed, however, in the responses of tissue obtained from fed and fasting rats to these compounds. The present results confirm previous observations and show the dependence of the lipolytic process on carbohydrate metabolism.

Adipose Tissue↗
PubMed1982

Interactions of the tau-tubulin-vinblastine complex with colchicine, podophyllotoxin, and N,N'-ethylenebis(iodoacetamide).

Microtubule assembly is inhibited by anti-mitotic drugs such as colchicine or podophyllotoxin and also by sulfhydryl-oxidizing reagents, but it is not known which tubulin-tubulin interactions are disrupted by these agents. We have studied the interactions of a complex of tubulin, vinblastine, and tau protein with these agents. This complex has the form of a spiral filament and may consist of tubulin dimers joined end to end as in a protofilament; presumably, therefore, the lateral interaction sites should be accessible in this structure but not in the intact microtubule. Unlike the microtubule, the complex binds to colchicine and podophyllotoxin with high affinity. Again, unlike intact microtubules, the complex reacts with N,N'-ethylene-bis(iodoacetamide) to generate an intra-chain cross-link in beta-tubulin. Tubulin molecules containing this cross-link are unable to polymerize, suggesting that formation of this cross-link involves sulfhydryl groups that are critical for assembly. These results are consistent with a model whereby colchicine-, podophyllotoxin-, and sulfhydryl-oxidizing agents inhibit microtubule assembly by preventing lateral interactions between tubulin molecules in adjacent protofilaments.

Animals↗
PubMed1981

Fluorimetry study of N-(1-pyrenyl)iodoacetamide-labelled F-actin. Local structural change of actin protomer both on polymerization and on binding of heavy meromyosin.

A fluorescent reagent, N-(1-pyrenyl)iodoacetamide, was conjugated to rabbit skeletal muscle actin at the site of the most reactive sulfhydryl group, and fluorescence characteristics (excitation and emission spectra, quantum yields, lifetimes) of the conjugate were investigated. Associated with polymerization of labelled G-actin, the fluorescence intensity at 407 nm, after excitation at 365 nm, was enhanced by a factor of about 25. It was reduced to about 25% on the binding of heavy meromyosin (or subfragment 1). The results suggest that binding of heavy meromyosin to the protomer of F-actin alters the local structure of the protomer towards a G-actin-like one.

Actins↗
PubMed1995

Rat epididymal sperm exhibit on dithiothreitol treatment in vitro quantifiable differences in patterns of light scatter, uptake of 14C-iodoacetamide and binding of ethidium bromide to DNA.

The extent to which chromatin of rat caput (CAP), corpus (COR), cauda (CAU) spermatozoa undergo condensation and compaction is known to be a function of progressive increase in the formation of inter- as well as intra-protamine disulphide bridges during their transit through the epididymis. Relative compaction undergone by the nuclear chromatin of these sperm populations was studied by monitoring their susceptibility to in vitro decondensation induced by varying concentrations (0, 0.01, 1, 5, 10, 50 mM) of disulphide reducing agent, dithiothreitol (DTT) after an initial exposure to 0.01% papain. Following this treatment and staining with the nucleic acid specific fluorochrome, ethidium bromide (EB), it was observed that irrespective of the epididymal region from which they were collected, spermatozoa exhibited DTT dose-dependent (a) increase in nuclear size as seen under fluorescence microscopic examination, (b) decrease in flow cytometrically quantifiable light scatter parameters--forward scatter (FSc, 'nuclear size') and side scatter (SSc, nuclear 'granularity'), (c) increase in individual cell EB binding when analyzed by DNA flow cytometry, and (d) increase in thiol specific 14C-iodoacetamide (14C-IA) uptake. The decrease in both FSc and SSc occurring in spite of actual increase in nuclear size has been attributed to increase in translucency of spermatozoan nuclei consequent to decondensation. The FSc, SSc and EB bindability were studied by monitoring both the channels of maximal cell concentration detected in the flow cytograms as well as by digitally quantitating the numbers of cells within specific channels (1-64, 65-128, 129-192 and 193-256) of the flow cytogram. The latter indicated a measure of the variability in the response of populations of sperm within each sample to DTT induced decondensation. At any given concentration of DTT, especially between 5-10 mM, the differences observed between sperms of different regions were consistent and significant (P < 0.01-P < 0.001), maximal changes being shown by CAP and minimal by CAU sperm, COR sperm appearing in between. The effective concentration of DTT required to elicit 50% of maximal (i.e. that exhibited by CAP sperm when taken as 100%) effect (ED50) varied significantly among CAP, COR and CAU sperms for each of the parameters studied (P < 0.01-P < 0.001). It is concluded that the differences observed among the three epididymal sperm populations are due to differences in the extent of susceptibility to decondensation in vitro and that this is dependent upon the variation in the -S-S-content of their chromatin during different stages of epididymal transit. All the parameters used (with the exception of fluorescence microscopy) can be quantified and as all of them show a similar dose dependency to DTT treatment, any one of these parameters can be conveniently used to determine the mature/immature status of the sperms voided. Application of such a method to determine the quality of sperms voided by man appears feasible.

Animals↗
PubMed1996

[Selective chemical modification of cytochrome P450scc (CYP11A1) with diiodofluorescein iodoacetamide in the study of the role and topology of interdomain hinge of the hemoprotein molecule].

Bovine adrenocortical cytochrome P450scc (CYP11A1) was selectively modified with diiodofluorescein iodoacetamide (DIFIA). Only Cys264 is labeled in the P450 polypeptide chain. The modification significantly affected the cholesterol-hydroxylating activity in the reconstituted system containing NADPH, adrenodoxin reductase, adrenodoxin, and soluble or membrane-bound P450scc. The inhibitory effect correlates with decreased affinity of cytochrome P450scc to intermediate electron carrier, adrenodoxin. Cytochrome P450scc is modified in liposomes and the modified membrane-bound protein is cleaved by trypsin forming two large fragments F1 and F2 corresponding to the N- and C-terminal regions of the molecule. The data indicate that the Cys264-containing region of the cytochrome P450scc molecule is exposed to the surface of protein globule, located outside of the membrane, and can participate in protein-protein interactions.

Adrenal Cortex↗