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PubMed2003

[Analysis of the growth system of Candida albicans in a host and the development of new antifungal material].

Hyphal cells of Candida albicans bind to human hemoglobin, but not yeast cells. The amount of hemoglobin receptor is significantly higher in hyphal cells than on yeast cells. Only the hyphal cells of C. albicans use hemoglobin as a source of iron. The culture supernatant of C. albicans promoted the disruption of human red blood cells (RBC). Hemolytic activity was detected in a sugar-rich fraction (about 200 kDa) purified by Sephacryl S-100 chromatography. As the hemolytic activity was adsorbed by concanavalin A (Con A)-Sepharose, the hemolytic factor might be a mannoprotein. The activity was inactivated by periodate oxidation, indicating that the sugar moiety of the mannoprotein plays an important role in hemolysis. The structure of the sugar moiety of the mannoprotein was identified as a cell wall mannan by 1H-NMR analysis, and purified C. albicans mannan promoted the disruption of RBC. The binding of mannan to RBC was demonstrated by flow cytometric analysis and was inhibited by the addition of the band 3 protein inhibitor, 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS). The hemolysis caused by mannan is inhibited by DIDS, 4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulfonic acid, and Bis (sulfosuccinimidyl) suberate, but not by pyridoxal-5'-phosphate. A new platinum derivative of the form H[Pt(IV) (Hdigly)Cl2(OH)2] (Hdigly = glycylglycine) has candidacidal activity 10-fold lower than that of cisplatin.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1990

Role of prostaglandin-H synthase in mediating genotoxic and carcinogenic effects of estrogens.

Diethylstilbestrol (DES) has been found to be oxidized in Syrian hamster embryo (SHE) cells by prostaglandin-H synthase (PGH synthase). It is hypothesized that PGH synthase mediates adverse effects of DES and other carcinogenic estrogens such as induction of neoplastic transformation and genotoxicity. Interest in PGH synthase-catalyzed reactions focuses on two aspects: oxidation and metabolic activation of stilbene and steroid estrogens by PGH synthase, and modulation of prostaglandin biosynthesis via effects of these compounds on PGH synthase. Studies of the former aspect of PGH synthase-catalyzed in vitro metabolism have revealed that cooxidation of DES, DES analogues, and steroid estrogens gives rise to reactive intermediates; DES and DES analogues known to transform SHE cells are metabolized by PGH synthase in vitro; PGH synthase catalyzes both the formation and oxidation of catechol metabolites from steroid estrogens, and reactive intermediates from DES and from steroid estrogens are stable enough to bind both to the catalytic enzyme PGH synthase and to other proteins. The data support the contention that PGH synthase-catalyzed metabolic activation plays a role in the induction of neoplastic transformation by stilbene and steroid estrogens but is not conclusive evidence for a cause-effect relationship. More recently, two closely related DES indanyl analogues have been found to differ in their interaction with PGH synthase: indenestrol A is cooxidized and activated like DES, whereas indenestrol B inhibits the enzyme. They provide useful tools to test the above hypothesis from a new perspective.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Rat and human liver cytosolic epoxide hydrolases: evidence for multiple forms at level of protein and mRNA.

Two forms of human liver cytosolic epoxide hydrolase (cEH) with diagnostic substrate specificity for trans-stilbene oxide (cEHTSO) and cis-stilbene oxide (cEHCSO) have been identified, and cEHCSO was purified to apparent homogeneity. The enzyme had a monomer molecular weight of 49 kDa and an isoelectric point of 9.2. Pure cEHCSO hydrolyzed CSO at a rate of 145 nmole/min/mg. TSO was not metabolized at a detectable level, and like cEHTSO, the enzyme was about three times more active at pH 7.4 than at pH 9.0. Unlike cEHTSO, cEHCSO was efficiently inhibited by 1 mM 1-trichloropropene oxide (90.5%) and 1 mM STO (92%). Similarly, liver cEH purified 541-fold from fenofibrate induced Fischer 344 rats was shown to be a native 120 kDa dimer of two 61 kDa subunits. The enzyme expressed maximum activity of 205 nmole/min/mg at pH 7.4 toward the diagnostic substrate TSO with an apparent Km of 1.7 microM. In Western blots, polyclonal antibodies against rat liver cEH were shown to recognize a single 61 kDa protein band from liver cytosol of rat, mouse, guinea pig, Syrian hamster, and rabbit. This antibody precipitated neither human liver cEHTSO or cEHCSO. Antibodies against rat liver microsomal epoxide hydrolase reacted with cEHCSO in the Western blot and on immunoprecipitation. Using antibodies against rat liver cEH, 24 positive clones were picked upon colony blot screening of a pEX 1/E. coli POP 2136 expression library.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Effects of estrogens on microtubule polymerization in vitro: correlation with estrogenicity.

Several estrogens of diverse classes, namely stilbene estrogens, steroidal estrogens, phytoestrogens, mycoestrogens, lignans, and bisphenol A, were studied for their ability to interfere with the assembly of microtubules under cell-free conditions. Inhibition of microtubules in intact cells may lead to the induction of micronuclei and aneuploidy and thereby contribute to estrogen-mediated carcinogenesis. Diethylstilbestrol and various other stilbene estrogens, as well as bisphenol A, were good inhibitors of microtubule polymerization whereas the other tested compounds were devoid of this activity. Therefore, the ability of estrogenic substances to interact with microtubules does not correlate with the hormonal activity.

Aneuploidy↗
PubMed2006

Identification of compounds associated with testosterone depressions in fish exposed to bleached kraft pulp and paper mill chemical recovery condensates.

In previous experiments, bleached kraft chemical recovery condensates generated during softwood pulp production have been identified as a primary source of substances causing testosterone depressions in mummichog (Fundulus heteroclitus). Recent toxicity identification evaluations have encountered inconsistencies in the potential of condensates and fractions to reduce steroid concentrations between three repeated exposures. To assess the sources of these inconsistencies, temporal assessments of condensate extractives and analytical methodologies were evaluated. Condensates were collected during a six-month period, extracted by solid-phase extraction (SPE), and analyzed by gas chromatography-mass spectrometry and gas chromatography-flame photometric detection. All unique extractives were cataloged by mass spectra, peak area, and gas chromatographic retention time, and nine were confirmed and quantified against authentic standards. Confirmed components included phenolic guaiacyl-based lignin degradation products, sulfur (S9), three diterpenoids, and a dimethoxy stilbene. Concentrations of confirmed condensate extractives were consistent in all samples collected. Spiking experiments of confirmed extractives revealed substantial losses following high-pressure liquid chromatographic fractionation and three different methods of fraction preparation. In an effort to propose chemical classes associated with biological activity, all unique condensate extractives in previously established bioactive and inactive fractions were classified based on their potential to depress testosterone in mummichog. Of 39 unique components in bioactive SPE extracts of condensates, six were associated with hormonal activity. Mass spectral interpretation indicated hydroxylated diterpenoids, sesquiterpenoids, and a lignin-derived stilbene as classes of chemicals associated with steroid depressions.

Animals↗
PubMedDate not supplied

Transmembrane helix-helix interactions and accessibility of H2DIDS on labelled band 3, the erythrocyte anion exchange protein.

4,4'-Diisothiocyanodihydrostilbene-2,2'-disulphonate (H2DIDS), a bifunctional inhibitor of anion exchange in erythrocytes, reacts with Lys-539 in band 3 at neutral pH and crosslinks to Lys-851 at alkaline pH. The accessibility of H2DIDS-labelled band 3 was determined using an anti-H2DIDS antibody and proteolysis. Competitive enzyme-linked immunosorbent assays (ELISAs) showed that a polyclonal antibody raised against H2DIDS-labelled keyhole limpet hemocyanin bound a variety of stilbene disulphonates in the following order of affinities, H2DIDS having the highest affinity: H2DIDS > 4,4'-diisothiocyanostilbene-2,2'-disulphonate (DIDS) > 4-acetamido-4'-isothiocyanostilbene-2,2'disulphonate (SITS) > 4,4'-dinitrostilbene-2,2'-disulphonate (DNDS) > 4,4'-diaminostilbene-2,2'-disulphonate (DADS). The antibody readily detected mono- or bifunctionally H2DIDS-labelled band 3 and proteolytic fragments on immunoblots. H2DIDS attached to Lys-539 is retained in a 7.5 kDa membrane-associated peptide after papain treatment of ghost membranes while the sequence around Lys-851 is more accessible. The band 3 proteolytic fragments protected by the membrane from proteolysis remained associated as a specific complex with a Stokes radius slightly smaller than the dimeric membrane domain after solubilization in detergent solution and retained 82% of the amino acid content of the membrane domain. Circular dichroism (CD) measurements of this H2DIDS-labelled complex showed that it had a very high helical content (86%). The loops connecting the transmembrane segments in H2DIDS-labelled band 3 are therefore not required to maintain transmembrane helix-helix interactions. Denatured band 3 prelabelled with H2DIDS was more readily immunoprecipitated with the anti-H2DIDS antibody than was native band 3 in detergent solution. Deglycosylation of band 3 or proteolytic cleavage of the extramembranous loops did not enhance immunoprecipitation of H2DIDS-labelled band 3. The stilbene disulphonate inhibitor site is therefore relatively inaccessible and is bound by a bundle of helices in the native band 3 protein.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1992

Electrogenic anion absorption in rabbit distal colon.

The mechanisms of anion transport in the rabbit distal colon were investigated in vitro under short-circuit conditions by examining the effects of transport inhibitors (the stilbene derivatives SITS and DIDS) under a variety of conditions. These agents consistently inhibited Jm-sCl: SITS (10(-3) M) reduced both unidirectional chloride fluxes to the same degree and did not alter JnetCl. In contrast, 10(-4) M DIDS had no effect on Js-mCl and had a significant chloride antiabsorptive effect. DIDS had no effect on either tissue cyclic AMP levels or on basal flux of potassium. The effects of SITS and the cyclic AMP-related secretagogue theophylline on Isc were independent. Additionally, there was no significant alteration of intracellular potential difference or apical membrane fractional resistance elicited by SITS during microelectrode impalement of colonic surface epithelial cells. These results suggest a complex mechanism of anion transport in the distal colon, with a component of electrogenic anion absorption inhibited by the stilbenes. The subsequent changes in current, conductance, and chloride fluxes are dependent upon additional, independent anion transport processes. These pharmacologic agents exhibit an antiabsorptive effect, rather than a stimulation of electrogenic chloride secretion.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2000

Chemoprevention of aflatoxin B1 hepatocarcinogenesis by coumarin, a natural benzopyrone that is a potent inducer of aflatoxin B1-aldehyde reductase, the glutathione S-transferase A5 and P1 subunits, and NAD(P)H:quinone oxidoreductase in rat liver.

Structurally diverse compounds can confer resistance to aflatoxin B1 (AFB1) hepatocarcinogenesis in the rat. Treatment with either phytochemicals [benzyl isothiocyanate, coumarin (CMRN), or indole-3-carbinol] or synthetic antioxidants and other drugs (butylated hydroxyanisole, diethyl maleate, ethoxyquin, beta-naphthoflavone, oltipraz, phenobarbital, or trans-stilbene oxide) has been found to increase hepatic aldo-keto reductase activity toward AFB1-dialdehyde and glutathione S-transferase (GST) activity toward AFB1-8,9-epoxide in both male and female rats. Under the conditions used, the natural benzopyrone CMRN was a major inducer of the AFB1 aldehyde reductase (AFAR) and the aflatoxin-conjugating class-alpha GST A5 subunit in rat liver, causing elevations of between 25- and 35-fold in hepatic levels of these proteins. Induction was not limited to AFAR and GSTA5: treatment with CMRN caused similar increases in the amount of the class-pi GST P1 subunit and NAD(P)H: quinone oxidoreductase in rat liver. Immunohistochemistry demonstrated that the overexpression of AFAR, GSTA5, GSTP1, and NAD(P)H:quinone oxidoreductase affected by CMRN is restricted to the centrilobular (periacinar) zone of the lobule, sometimes extending almost as far as the portal tract. This pattern of induction was also observed with ethoxyquin, oltipraz, and trans-stilbene oxide. By contrast, induction of these proteins by beta-naphthoflavone and diethyl maleate was predominantly periportal. Northern blotting showed that induction of these phase II drug-metabolizing enzymes by CMRN was accompanied by similar increases in the levels of their mRNAs. To assess the biological significance of enzyme induction by dietary CMRN, two intervention studies were performed in which the ability of the benzopyrone to inhibit either AFB1-initiated preneoplastic nodules (at 13 weeks) or AFB1-initiated liver tumors (at 50 weeks) was investigated. Animals pretreated with CMRN for 2 weeks prior to administration of AFB1, and with continued treatment during exposure to the carcinogen for a further 11 weeks, were protected completely from development of hepatic preneoplastic lesions by 13 weeks. In the longer-term dietary intervention, treatment with CMRN before and during exposure to AFB1 for a total of 24 weeks was found to significantly inhibit the number and size of tumors that subsequently developed by 50 weeks. These data suggest that consumption of a CMRN-containing diet provides substantial protection against the initiation of AFB1 hepatocarcinogenesis in the rat.

Aflatoxin B1↗
PubMedDate not supplied

Cytotoxic and DNA damage-inducing activities of low molecular weight phenols from rhubarb.

Six new phenol (anthraquinone or stilbene) glycosides with an acyl group at 6-position of the glucopyranose moiety were isolated from rhubarb (the roots of Rheum palmatum) cultivated in Japan, together with 22 known compounds. Most of these compounds were evaluated for cytotoxic activity against tumor and normal cells and for induction of DNA damage by spore rec-assay. Among them, emodin and aloe-emodin showed higher cytotoxic activities against human oral squamous cell carcinoma (HSC-2) and salivary gland tumor (HSG) cell lines than against normal human gingival fibroblasts (HGF). Chrysophanol 8-O-beta-(6'-acetyl)glucopyranoside, 4-(4'-hydroxyphenyl)-2-butanone 4'-O-beta-D-(2"-O-galloyl-6"-O-cinnamoyl) glucopyranoside, and 6"-O-(4'''-hydroxybenzoyl) resveratroloside exhibited relatively higher cytotoxic activities against all these cells. The other glycosides of anthraquinone or stilbene showed weaker cytotoxic activity against these tumor cell lines, but may be considered as cancer chemopreventive agents. Spore rec-assay with a recombination deficient mutant of Bacillus subtilis M45 demonstrated the DNA damage-inducing activity of emodin and aloe-emodin 15-O-beta-D-glucopyranoside among, rhubarb phenols.

Bacillus subtilis↗
PubMed2002

Influence of ion channels on the proliferation of human chondrocytes.

The goal of the study was to examine connections between ion channel activity and the proliferation of human chondrocytes. Chondrocytes were isolated form human osteoarthritic knee joint cartilage. In this study the concentration-dependent influence of the ion channel modulators tetraethylammonium (TEA), 4-aminopyridine (4-AP), 4',4' diisothiocyanato-stilbene-2,2'-disulfonic acid (DIDS), 4-acetamido-4'-isothiocyano-2,2'-disulfonic acid stilbene (SITS), verapamil (vp) and lidocaine (lido) on the membrane potential and the proliferation of human chondrocytes was investigated using flow cytometry and the measurement of (3)H-thymidine incorporation as measure for the cell proliferation. The results show an effect of the used ion channel modulators causing a change of the membrane potential of human chondrocytes. The maximal measurable effects of the membrane potential were listed with 0.25 mmol/l verapamil (-18%) and 0.1 mmol/l lidocaine (+20%). When measuring DNA distribution, it became apparent that the human chondrocytes are diploid cells with a very low proliferation tendency. After 12 days culture duration, lidocaine and 4-AP cause an increase of the DNA synthesis rate being a limited effect. These results allow the conclusion of an influence of ion channel modulators on chondrocyte proliferation. To gain knowledge of the regulation of chondrocyte proliferation via ion channel modulators could serve the research of new osteoarthritis treatment concepts.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2003

[Study on quality standard for heshouwu dispensing granule].

OBJECTIVE: To study the quality standard for Heshouwu dispensing granule. METHODS: Heshouwu dispensing granule was identified by TLC and 2,3,5,4'-tetrahydroxy-stilbene-2-O-beta-D-glucoside in Heshouwu dispensing granule were determined by HPLC. RESULTS: The linear relationship was at the range of 0.4028-3.6252 micrograms and the average recovery was 101.15%, RSD = 2.00% for 2,3,5,4'-tetrahydroxy-stilbene-2-O-beta-D-glucoside. CONCLUSION: The methods were available with a good reproducibility and can be used to control the quality of Heshouwu dispensing granule.

Drugs, Chinese Herbal↗
PubMed1992

Effect of diethylstilbestrol and related compounds on the Ca(2+)-transporting ATPase of sarcoplasmic reticulum.

Diethylstilbestrol is a potent inhibitory agent of the Ca(2+)-ATPase activity of sarcoplasmic reticulum membranes. Other structurally related molecules, such as dienestrol or hexestrol having hydroxyl groups at para positions of the two benzene rings produce similar effects. The absence or derivatization of the hydroxyl groups as occurs with trans-stilbene or diethylstilbestrol dipropionate converts the structure in an activating agent of the enzyme. The Ca2+ transport profiles in the presence of the referred drugs reproduces the same behavior observed for the hydrolytic activity. There is also a clear indication of a membrane-mediated mechanism of these drugs. Ligand binding experiments at equilibrium indicate that diethylstilbestrol decreases the affinity for Ca2+ of the high affinity Ca2+ sites. Functional studies reveal that the activation/inhibition induced by these drugs is correlated with decreased levels of phosphoenzyme at steady state, and these levels are sensitive to the Ca2+ concentration. Chase experiments of [32P]phosphoenzyme and 45Ca2+ indicate a slight activation effect of diethylstilbestrol dipropionate on Ca2+ dissociation during the enzyme turnover. The use of different anthroyloxy derivatives of stearic acid as a fluorescent probe suggest that diethylstilbestrol and other inhibitory agents could be located close to the polar region of the lipid bilayer, which interferes with the Ca(2+)-binding sites, whereas the activators trans-stilbene and diethylstilbestrol dipropionate may have a deeper position into the membrane, which accelerates the Ca2+ translocation process.

Adenosine Triphosphate↗
PubMedDate not supplied

Quantitative imaging of cell-permeable magnetic resonance contrast agents using x-ray fluorescence.

The inability to transduce cellular membranes is a limitation of current magnetic resonance imaging probes used in biologic and clinical settings. This constraint confines contrast agents to extracellular and vascular regions of the body, drastically reducing their viability for investigating processes and cycles in developmental biology. Conversely, a contrast agent with the ability to permeate cell membranes could be used in visualizing cell patterning, cell fate mapping, gene therapy, and, eventually, noninvasive cancer diagnosis. Therefore, we describe the synthesis and quantitative imaging of four contrast agents with the capability to cross cell membranes in sufficient quantity for detection. Each agent is based on the conjugation of a Gd(III) chelator with a cellular transduction moiety. Specifically, we coupled Gd(III)-diethylenetriaminepentaacetic acid DTPA and Gd(III)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid with an 8-amino acid polyarginine oligomer and an amphipathic stilbene molecule, 4-amino-4'-(N,N-dimethylamino)stilbene. The imaging modality that provided the best sensitivity and spatial resolution for direct detection of the contrast agents is synchrotron radiation x-ray fluorescence (SR-XRF). Unlike optical microscopy, SR-XRF provides two-dimensional images with resolution 10(3) better than (153)Gd gamma counting, without altering the agent by organic fluorophore conjugation. The transduction efficiency of the intracellular agents was evaluated by T(1) analysis and inductively coupled plasma mass spectrometry to determine the efficacy of each chelate-transporter combination.

Animals↗
PubMedDate not supplied

Stereoselective glucuronidation as a probe of induced forms of UDP-glucuronyltransferase in rabbits.

Stereoselective glucuronidation of the chiral drug oxazepam by hepatic microsomes from rabbits pretreated with various inducers was used to characterize induced UDP-glucuronyltransferase (GT) enzymes. The enzymes were induced by pretreatment of rabbits with phenobarbital, DDT, 3-methylcholanthrene, beta-naphthoflavone, ethanol, trans-stilbene oxide, pregnenolone-16 alpha-carbonitrile, Aroclor 1254, and clofibric acid. Hepatic microsomes from induced and control animals were incubated with racemic oxazepam and the activator, Lubrol PX. Relative amounts of the diastereomeric beta-glucuronides were determined by HPLC. Significant differences were found in enantiomeric selectivity among the microsomes from rabbits pretreated with different inducers. The largest difference in diastereomeric glucuronide ratios observed was between control (R/S = 0.76) and beta-naphthoflavone-induced microsomes (R/S = 1.41). This demonstrated a significant change in enantiomeric selectivity by the enzymes, changing from preference for the S enantiomer in controls to its R antipode after induction. Differences in stereoselectivity between two members of a class of inducers such as 3-methylcholanthrene (R/S = 1.16) and beta-naphthoflavone (R/S = 1.41), provided evidence for possible distinctions between these similar inducers. Inducers of GT1 UDP-glucuronyltransferase enzyme forms, such as 3-methylcholanthrene, beta-naphthoflavone, and Aroclor 1254, did not increase the rate of formation of oxazepam glucuronides. All other inducers except DDT increased the rate of oxazepam glucuronidation by 20-53% with the highest rate (0.23 nmol/min X mg protein) occurring after trans-stilbene oxide induction. UDP-N-acetylglucosamine was also used as an activator to provide a comparison of the Lubrol-activated microsomes with the endogenous activator. Relative differences among inducers were approximately the same with both activators.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Role of a Na+-dependent Cl-/HCO3- exchange in regulation of intracellular pH in fibroblasts.

We previously reported that, in a HCO3(-)-free medium, cytoplasmic pH (pHi) of hamster fibroblasts (CCL39) is primarily regulated by an amiloride-sensitive Na+/H+ antiport (L'Allemain, G., Paris, S., and Pouysségur, J. (1984) J. Biol. Chem. 259, 5809-5815). Here we demonstrate the existence of an additional pHi-regulating mechanism in CCL39 cells, namely a Na+-dependent HCO3-/Cl- exchange. Evidence for this system is based on 36Cl- influx studies and on pHi measurements in PS120, a CCL39-derived mutant lacking the Na+/H+ antiport activity. 36Cl- influx rate is a saturable function of external [Cl-] (apparent Km approximately equal to 7 mM), is competitively inhibited by external HCO3- (KI approximately equal to 3 mM), and by stilbene derivatives (KI approximately equal to 20 microM for 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid). Measurements of pHi recovery after an acute acid load indicate that PS120 cells possess an acid-extruding mechanism dependent on external HCO3-, which is inhibited by stilbene derivatives and requires external Na+. Since 22Na+ influx is stimulated upon addition of HCO3- to acid-loaded cells and this effect is completely abolished by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, we conclude that Na+ is co-transported with HCO3-, in exchange for intracellular Cl-. In a HCO3(-)-containing medium, this pHi-regulating mechanism appears to have two essential physiological functions for the Na+/H+ antiport-deficient mutant: protection of the cells against excessive cytoplasmic acidification and establishment of a steady-state pHi permissive for growth, at neutral or slightly acidic pHo values (6.6-7.2).

Amiloride↗
PubMed1987

Alteration of Trichostrongylus colubriformis egg permeability by Bacillus thuringiensis israelensis toxin.

A toxin from the bacterium Bacillus thuringiensis israelensis is lethal to nematode eggs. Exposure of eggs of the ruminant nematode Trichostrongylus colubriformis to the toxin significantly increased the eggs' permeability to radiolabeled phenylalanine within 2 hr. Calcium chloride inhibited the toxin-induced change in egg permeability. Iodine staining of eggs that were exposed to the microbial toxin revealed that egg permeability was altered within 5 min and was dependent on the dose of toxin. Addition of 34 mM sucrose, 17 mM sodium chloride, or 17 mM potassium chloride to the eggs' medium increased the toxin's lethality. Exopeptidase activity in eggs of T. colubriformis was reduced significantly after exposure to the B. t. israelensis toxin. Tetrodotoxin, tetraethylammonium chloride, ouabain, 4-acetamido-4'-isothiocyano-stilbene-2,2'disulfonic acid (SITS), 4,4'-diisothiocyano-2,2'disulfonic acid stilbene (DIDS), valinomycin, and sodium vanadate, which affect membrane transport, had no significant effect on the activity of B. t. israelensis toxin for eggs. Likewise, a series of nucleotides and their derivatives had no effect on the toxin's activity. Ovicidal activity of the microbial toxin was increased by 4-aminopyridine (4.4 X), but was decreased by furosemide (97 X), nigericin (263 X), or monensin (125 X). Microscopic measurement of T. colubriformis eggs after treatment with the microbial toxin revealed no significant size change.

Animals↗
PubMedDate not supplied

A comparative study of benzo[a]pyrene hydroxylase and epoxide hydrolase derived from isolated rat hepatic nuclei and microsomes.

Several properties of benzo[a]pyrene hydroxylase (AHH) and epoxide hydrolase (EH) in isolated rat hepatic nuclei were investigated. Comparisons were made with microsomal AHH and EH in order to determine whether the nuclear enzymes were distinct from those of endoplasmic reticulum origin. The ratio of EH to AHH in the nuclei of adult male rats was 4.5 compared to 1.6 in the microsomes. Phenobarbital increased AHH in nuclei from immature males and females. However, the increase were markedly lower than those observed in the microsomes. In contrast, 3-methylcholanthrene increased nuclear AHH to a greater extent than the microsomal enzyme. The age and sex dependence, the inhibition by SKF 525-A, the stimulatory and inhibitory effects of 7,8-benzoflavone and the decrease produced by trans-stilbene oxide administration were the same for both nuclear and microsomal AHH. Phenobarbital, l-alpha-acetyulmethadol, and trans-stilbene oxide increased nuclear EH. The increases were approximately 3-fold lower than observed in the microsomes. EH activity in both nuclei and microsomes was inhibited by 1,2-epoxy-3,3,3-trichloropropane. The data indicate that both the constitutive and induced form(s) of AHH in isolated nuclei and endoplasmic reticulum have a number of common properties. The constitutive form(s) of microsomal and nuclear EH also appear to be similar. However, AHH and EH in isolated nuclei differ from their microsomal counterparts in quantitative inducibility. These differences in inducibility support the suggestion that AHH and EH are located in isolated nuclei rather than resulting from contamination by endoplasmic reticulum.

Animals↗
PubMed1984

An osmotic mechanism for exocytosis from dissociated chromaffin cells.

Dissociated chromaffin cells from bovine adrenal medulla were stimulated to secrete epinephrine and dopamine beta-hydroxylase with a variety of secretagogues in a study designed to test the hypothesis that the chemiosmotic lysis reaction of isolated chromaffin granules might in some way be related to the mechanism of release during exocytosis. Increasing the osmotic strength of the incubation medium with either NaCl or sucrose led to suppression of secretion of epinephrine from the cells regardless of whether secretion was induced with veratridine or acetylcholine. Suppression of secretion was approximately exponential with respect to osmotic strength. Epinephrine secretion occurred only if the medium contained a permeant anion such as chloride, and secretion induced by veratridine was suppressed when Na isethionate replaced NaCl in the medium. In an extensive study with different monovalent anions veratridine supported epinephrine secretion according to the following activity series: Br-, I-, NO3- greater than methylsulfate, SCN- greater than Cl greater than acetate much greater than isethionate. A similar series, except for the potency of NO3-, was observed with A23187 as agonist. In general, the anion series for granule lysis was analogous. However, there was a poor quantitative correlation between the anion dependence of chemiosmotic granule lysis and the anion dependence of cell secretion. Anion transport inhibitors such as probenecid and pyridoxal phosphate also inhibited secretion while the stilbene disulfonates were inactive. The ineffectiveness of the stilbene disulfonates further distinguished chemiosmotic granule lysis from cell secretion. Secretion of catecholamines, induced by veratridine or nicotine, a cholinergic agonist, was suppressed when NaCl in the medium was replaced by isosmotic sucrose and unexpectedly low levels of dopamine beta-hydroxylase were observed in some cases. In sum, these properties of secreting chromaffin cells resembled some properties of isolated chromaffin granules incubated in ATP and Cl-, but were different in a number of instances. We, therefore, have interpreted our data to indicate that while some mechanistic relationships may indeed exist between the release event in exocytosis from chromaffin cells and the chemiosmotic lysis reaction characteristic of isolated chromaffin granules, an understanding of the energetics of exocytosis awaits the discovery of reasons for the quantitative differences between the two systems.

Adrenal Medulla↗