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At least 235 records · Page 13Linked to original sources
PubMed1986

The formation of styrene glutathione adducts catalyzed by prostaglandin H synthase. A possible new mechanism for the formation of glutathione conjugates.

The metabolism of styrene by prostaglandin hydroperoxidase and horseradish peroxidase was examined. Ram seminal vesicle microsomes in the presence of arachidonic acid or hydrogen peroxide and glutathione converted styrene to glutathione adducts. Neither styrene 7,8-oxide nor styrene glycol was detected as a product in the incubation. Also, the addition of styrene 7,8-oxide and glutathione to ram seminal vesicle microsomes did not yield styrene glutathione adducts. The peroxidase-generated styrene glutathione adducts were isolated by high pressure liquid chromatography and characterized by NMR and tandem mass spectrometry as a mixture of (2R)- and (2S)-S-(2-phenyl-2-hydroxyethyl)glutathione. (1R)- and (1S)-S-(1-phenyl-2-hydroxyethyl)glutathione were not formed by the peroxidase system. The addition of phenol or aminopyrine to incubations, which greatly enhances the oxidation of glutathione to a thiyl radical by peroxidases, increased the formation of styrene glutathione adducts. We propose a new mechanism for the formation of glutathione adducts that is independent of epoxide formation but dependent on the initial oxidation of glutathione to a thiyl radical by the peroxidase, and the subsequent reaction of the thiyl radical with a suitable substrate, such as styrene.

Animals↗
PubMed1985

Formation and release of eukaryotic initiation factor 2 X GDP complex during eukaryotic ribosomal polypeptide chain initiation complex formation.

The formation and release of an eukaryotic initiation factor (eIF)-2 X GDP binary complex during eIF-5-mediated assembly of an 80 S ribosomal polypeptide chain initiation complex have been studied by sucrose gradient centrifugation analysis. Isolated 40 S initiation complex reacts with eIF-5 and 60 S ribosomal subunits to form an 80 S ribosomal initiation complex with concomitant hydrolysis of an equimolar amount of bound GTP to GDP and Pi. Sucrose gradient analysis of reaction products revealed that GDP was released from ribosomes as an eIF-2 X GDP complex. Evidence is presented that eIF-5-mediated hydrolysis releases the GTP bound to the 40 S initiation complex as an intact eIF-2 X GDP complex rather than as free GDP and eIF-2 which subsequently recombine to form the binary complex. Furthermore, formation and release of eIF-2 X GDP from the ribosomal complex do not require concomitant formation of an 80 S initiation complex since both reactions occur efficiently when the 40 S initiation complex reacts with eIF-5 in the absence of 60 S ribosomal subunits. These results, along with the observation that the 40 S initiation complex formed with the nonhydrolyzable analogue of GTP, 5'-guanylylmethylene diphosphonate, can neither join a 60 S ribosomal subunit nor releases ribosome-bound eIF-2, suggest that following eIF-5-mediated hydrolysis of GTP bound to the 40 S initiation complex, both Pi and eIF-2 X GDP complex are released from ribosomes prior to the joining of 60 S ribosomal subunits to the 40 S initiation complex.

Animals↗
PubMed1976

Reaginic antibody formation in the mouse. VII. Depression of the ongoing IgE antibody formation by suppressor T cells.

The ongoing IgE antibody formation against ovalbumin (OA) in high responder mice was depressed by i.v. injections of either native or urea-denatured ovalbumin (UD-OA). Adoptive transfer experiments to determine the helper function of spleen cells from the treated animals showed that helper function for both IgE and IgG antibody responses diminished after treatment. Evidence was obtained that treatment suppressed the expansion of IgE-G memory cells. When the same treatment with OA or UD-OA was given to OA-primed mice before the appearance of IgE antibody in their serum, OA-specific splenic suppressor T cells were demonstrable. Thus, the transfer of splenic T cells from treated mice into normal mice suppressed the primary IgE and IgG antibody responses of the recipeints to DNP-OA. It was also found that the transfer of the splenic T cells from UD-OA-treated mice into OA-primed mice depressed ongoing IgE antibody formation in the recipients. The results suggested strongly that the decrease of helper function and the depression of ongoing IgE antibody formation by repeated injections of UD-OA was caused by generation of antigen (OA)-specific suppressor T cells.

Animals↗
PubMed1983

Drug interactions. II. Formation of nitrosamines from therapeutic drugs. Properties and kinetics of the formation of N-nitrosopropranolol from nitrite and the secondary amine propranolol hydrochloride.

In the presence of hydrochloric acid, nitrosamines may be generated from amines and nitrite. Most nitrosamines are carcinogens and many commonly used drugs contain potentially nitrosatable amine groups. Beta-adrenergic blockers, which have such amine groups, are widely prescribed and are often ingested for the lifetime of the patients, but their safety with respect to the intragastric formation of nitrosamines has not been established. The studies in this and the following report were designed to assess the potential risk posed by the endogenous formation of a nitrosamine in the stomach to individuals receiving longterm treatment with propranolol hydrochloride. The putative nitrosamine, N-nitrosopropranolol (NNP), was synthesized and its stability was examined under various experimental conditions. A high-pressure liquid chromatographic method was developed which detects a minimum of 7 X 10(-11) mol of NNP in the presence of large quantities of unreacted drug. Preparations of propranolol hydrochloride were found to contain several non-nitrosamine contaminants, which were removed before kinetic studies. At 37 degrees C, in solutions of HCl within the pH range found in the stomach, the optimum pH for the formation of NNP was 3. The yield of NNP increased linearly as incubation time and concentration of propranolol increased and exponentially as the concentration of nitrite was raised. Under optimal conditions in hydrochloric acid, the minimum concentration of nitrite required for the production of detectable amounts of NNP was 10(-5) M.

Chemical Phenomena↗
PubMed1977

[Processes of spore formation and gramicidin C formation by Bacillus brevis var. G.B].

Correlation between gramidicin C biosynthesis and sporulation in the process of Bac. brevis var. G.B. cultivation under various aeration conditions was studied. It was shown that biosynthesis of gramicidin C was characteristic of the young cells and its level was the highest during the culture active growth. The time of the sporulating forms appearance depended on the aeration rate which defined the quantitative composition of the population during the phase of the culture active growth and the stationary phase. Under the optimal aeration conditions the spore formation started during the phase of the culture active growth after some decrease in the maximum level of the cell productivity with respect to the antibiotic. When the aeration rate was increased the spore formation was shifted to later periods of the culture development, i.e. the stationary phase and the phase of the cell autolysis, the gap between the highest levels of gramicidin C buosynthesis and the beginning of sporulation being increased. Under certain aeration conditions the spore formation was not observed, while gramicidin C was synthesized. A conclusion has been made that there is no correlation between gramacidine C biosynthesis and sporualtion in Bacillus brevis var. G.B.

Air↗
PubMed1982

Cellular regulation of lung granuloma formation and delayed- type hypersensitivity induced with BCG cell walls. Further evidence of involvement of cellular immunity in lung granuloma formation.

We have previously showed several evidences in which cellular immunity is involved in lung granuloma formation induced with oil-associated BCG cell wall (CW) vaccine. In the present study, we examined in mice the effects of thymectomy, splenectomy and the administration of cyclophosphamide on lung granuloma formation as well as BCG CW-induced footpad reactions to PPD, a prototype of delayed-type hypersensitivity (DTH). The results presented herein provide further evidence that cellular immunoregulatory mechanisms control the development of lung granuloma and DTH, and that lung granuloma formation is thymus- and spleen-dependent.

Animals↗
PubMed1995

Gonadotropin-releasing hormone agonist therapy reduces postoperative adhesion formation and reformation after adhesiolysis in rat models for adhesion formation and endometriosis.

OBJECTIVES: To evaluate the effectiveness of GnRH agonist (GnRH-a) therapy on adhesion formation and reformation in established rat models for surgically induced adhesion formation and endometriosis. DESIGN: Before surgery, female Sprague-Dawley rats were injected with GnRH-a or control diluent. Six days later, rats were assigned to one of four surgical groups: [1] endometriosis, [2] endometriosis sham, [3] adhesion model, or [4] adhesion sham. Three weeks after surgery, a second-look laparotomy was performed, adhesions were scored (0 = no adhesions to 3 = severe adhesions) and mechanically disrupted, and rats received a second GnRH-a or diluent injection either analogous to their initial injection or in a crossover design. Three weeks after the second injection, rats were killed and adhesion reformation was scored. Data were evaluated using nonparameteric tests including Mann-Whitney, Kruskal-Wallis, and Friedman's tests comparing GnRH-a treatments with diluent controls. RESULTS: Preoperative GnRH-a therapy reduced adhesion scores in rats with surgically induced endometriosis (mean +/- SEM; GnRH-a 1.1 +/- 0.2 versus diluent 2.2 +/- 0.2) and adhesions (GnRH-a 0.3 +/- 0.1 versus diluent 0.6 +/- 0.1). Pretreatment GnRH-a therapy did not affect adhesion scores in the endometriosis sham procedure. Combined preoperative and postoperative GnRHa therapy (GnRH-a-GnRH-a) but not postoperative GnRH-a therapy alone (diluent-GnRH-a) reduced adhesion reformation after adhesiolysis in the endometriosis model (GnRH-a-GnRH-a 1.1 +/- 0.3, diluent-GnRH-a 1.6 +/- 0.7), the endometriosis sham (GnRH-a-GnRH-a 0.7 +/- 0.2, diluent-GnRHa 1.8 +/- 0.1), and the adhesion model (GnRH-a-GnRH-a 0.3 +/- 0.2, diluent-GnRHa 1.0 +/- 0.5). No adhesions were observed in the adhesion sham group. CONCLUSIONS: Gonadotropin-releasing hormone agonist therapy was successful in reducing adhesion formation and reformation. These studies suggest that GnRH-a therapy for adhesion prevention in women should be explored.

Animals↗
PubMed1994

Thrombin-Hirudin complex formation, thrombin-antithrombin III complex formation, and thrombin generation after intrinsic activation of plasma.

To investigate the relative importance of direct inhibition of thrombin by complex formation and of inhibition of thrombin generation to the mechanisms by that unfractionated heparin (UH) and recombinant hirudin (rH) exert their anticoagulant effects, thrombin-antithrombin III complex (TAT) and thrombin-hirudin complex (THC) formation was compared with the generation of thrombin and prothrombin fragments 1 + 2 (F 1 + 2). Clotting was initiated by activation of citrated plasma in the absence or presence of UH or rH using partial thromboplastin, ellagic acid and calcium chloride. THC was determined by means of ELISA using specific antibodies to thrombin and rH. Activation of citrated plasma resulted in a sudden onset of thrombin generation after a lag phase of 2 min. Addition of 50 ng rH/ml plasma or 0.1 UH/ml plasma prolonged the clotting time to 3 min. While the peak of thrombin was only slightly decreased in hirudinized plasma, in heparinized plasma thrombin generation was significantly lower than in not anticoagulated plasma. This difference was more pronounced when the lag phase was prolonged to 5 min using 400 ng rH/ml plasma or 0.35 U UH/ml plasma. Using 1200 ng rH/ml or 0.65 U UH/ml to obtain a clotting time of 9 min only a small amount of thrombin could be detected in heparinized plasma, but hirudinized plasma still showed a high peak of thrombin. F 1 + 2 showed essentially the same pattern as thrombin. Prior to the onset of visible clot formation in all experiments using different concentrations of UH about the same values of TAT were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Antithrombin III↗
PubMedDate not supplied

Role of 5-hydroxytryptamine in platelet thrombus formation and mechanisms of inhibition of thrombus formation by 5-hydroxytryptamine2A antagonists in rabbits.

The role of 5-hydroxytryptamine (5-HT) in platelet thrombus formation and in the mechanisms of inhibition of thrombus formation by 5-HT2A antagonists was investigated using a turbidimetric method. Collagen-induced platelet aggregation occurred simultaneously with a release of 5-HT from the platelets. The supernatant of collagen-aggregated platelets induced a further aggregation volume-dependently. This supernatant-induced aggregation was inhibited by either 5-HT2A antagonists or adenosine-diphosphate (ADP) scavenging. 5-Hydroxytryptamine and a small amount of the supernatant shifted the dose-response curves of collagen to the left. The aggregation velocity and the onset of aggregation by collagen were significantly increased by the supernatant, but not by 5-HT. The 5-HT2A antagonists, ketanserin and MCI-9042, returned the dose-response curves of the maximum aggregation and of the aggregation velocity of collagen, which were already amplified by the supernatant, to the original values. The onset of aggregation was delayed by the antagonists, but was not completely returned to the original points. There were distinct differences between the effects of endogenous 5-HT, derived from platelets which were stimulated by collagen, and those of exogenous 5-HT on both extensive platelet activation and amplification of the collagen-induced aggregation. These findings suggest that endogenous 5-HT activates platelets in synergism with ADP. The 5-HT2A antagonists used, block the synergism via 5-HT2A receptors and lead to inhibition of a positive feedback loop of thrombus formation.

Adenosine Diphosphate↗
PubMed2003

Incorporation of either molybdenum or tungsten into formate dehydrogenase from Desulfovibrio alaskensis NCIMB 13491; EPR assignment of the proximal iron-sulfur cluster to the pterin cofactor in formate dehydrogenases from sulfate-reducing bacteria.

We report the characterization of the molecular properties and EPR studies of a new formate dehydrogenase (FDH) from the sulfate-reducing organism Desulfovibrio alaskensis NCIMB 13491. FDHs are enzymes that catalyze the two-electron oxidation of formate to carbon dioxide in several aerobic and anaerobic organisms. D. alaskensis FDH is a heterodimeric protein with a molecular weight of 126+/-2 kDa composed of two subunits, alpha=93+/-3 kDa and beta=32+/-2 kDa, which contains 6+/-1 Fe/molecule, 0.4+/-0.1 Mo/molecule, 0.3+/-0.1 W/molecule, and 1.3+/-0.1 guanine monophosphate nucleotides. The UV-vis absorption spectrum of D. alaskensis FDH is typical of an iron-sulfur protein with a broad band around 400 nm. Variable-temperature EPR studies performed on reduced samples of D. alaskensis FDH showed the presence of signals associated with the different paramagnetic centers of D. alaskensis FDH. Three rhombic signals having g-values and relaxation behavior characteristic of [4Fe-4S] clusters were observed in the 5-40 K temperature range. Two EPR signals with all the g-values less than two, which accounted for less than 0.1 spin/protein, typical of mononuclear Mo(V) and W(V), respectively, were observed. The signal associated with the W(V) ion has a larger deviation from the free electron g-value, as expected for tungsten in a d(1) configuration, albeit with an unusual relaxation behavior. The EPR parameters of the Mo(V) signal are within the range of values typically found for the slow-type signal observed in several Mo-containing proteins belonging to the xanthine oxidase family of enzymes. Mo(V) resonances are split at temperatures below 50 K by magnetic coupling with one of the Fe/S clusters. The analysis of the inter-center magnetic interaction allowed us to assign the EPR-distinguishable iron-sulfur clusters with those seen in the crystal structure of a homologous enzyme.

Chromatography, Gel↗
PubMed1983

Production of auto-anti-idiotypic antibody during the normal immune response. VI. Hapten augmentation of plaque formation and hapten-reversible inhibition of plaque formation as assays for anti-idiotype antibody.

(1) Evidence has been presented that the detection of hapten-augmentable plaques indicates cells whose secretion of antibody had been blocked by the binding of auto-anti-id to cell surface idiotypes. Because of the dependence of the assay on the affinities of the various species for one another, the number of hapten-augmentable plaques detected should be regarded as a minimal estimate of the number of cells whose secretion of antibody is inhibited by auto-anti-id. For confirmation that hapten-augmentable PFC are due to auto-anti-id 2 principal controls are important: (a) incubation of the spleen cell population with hapten prior to plaquing should remove the hapten-augmentable PFC; (b) the dialyzed supernate from hapten incubated cells should inhibit plaque formation in a hapten-reversible manner. (2) Evidence has been presented that hapten-reversible inhibition of plaque formation can serve as an assay for anti-id. Apparent false positive assays can result from the presence of anti-hapten antibody or antigen-antibody complexes; however, these apparent false positives are rarely reversed by hapten. Removal of anti-hapten antibody, by passage over an antigen immunoadsorbent, will eliminate this source of false positives and the procedure is recommended. False negative results can arise from mismatching of the anti-ids in the sample to be assayed and the idiotypes of the target cells used in the assay. This can result from shifts in idiotype expression related to age and time after antigen injection. False negatives can also result from the presence of idiotype-anti-id complexes in the sample to be assayed. This source of false negatives can sometimes be eliminated by passage of the sample through an antigen immunoadsorbent.

Animals↗
PubMed1961

Antibody formation. I. The suppression of antibody formation by passively administered antibody.

The suppression of antibody formation by passively administered antibody is influenced by the dose and nature of the antigen, type of immunization procedure, ratio of antibody to antigen, species origin and characteristics of the antiserum used, as well as the species selected for immunization. In guinea pigs, diphtheria antitoxin formation can be effectively suppressed by an intravenous injection of excess homologous or heterologous antitoxin as long as 5 days after toxoid immunization and after delayed-type hypersensitivity to toxoid has developed. Following the period of antibody suppression which lasts 2 to 7 weeks, serum antibody can usually be demonstrated. It is proposed that this delayed immunization results from dissociation of antigen, since diphtheritic paralysis and death can be produced in guinea pigs and rabbits by the intravenous injection of toxin-antitoxin precipitates formed in antitoxin excess. This syndrome is prevented by injection of excess horse antitoxin 1 hour after injection of the toxin-antitoxin complexes.

Animals↗
PubMed2002

Cloning, nucleotide sequencing, and expression in Escherichia coli of the gene for formate dehydrogenase of Paracoccus sp. 12-A, a formate-assimilating bacterium.

The gene for the NAD-dependent formate dehydrogenase (FDH) of Paracoccus sp. 12-A, a formate-assimilating bacterium, was cloned through screening of the genomic library with activity staining. The FDH gene included an open reading frame of 1,200 base pairs, and encoded a protein of 43,757 Da, which had high amino acid sequence identity with known FDHs, in particular, with bacterial enzymes such as those of Moraxella sp. (86.5%) and Pseudomonas sp. 101 (83.5%). The gene was highly expressed in Escherichia coli cells using an expression plasmid with the pUC ori and tac promoter. The recombinant enzyme was somewhat inactive in the stage of the cell-free extract, but its activity markedly increased with purification, in particular, with the step of heat-treatment at 50 degrees C. The purified enzyme showed essentially the same properties as the enzyme from the original Paracoccus cells.

Amino Acid Sequence↗
PubMed1986

A PCILO study of the pharmacologically active conformation of local anesthetics of the procaine type. Conformational analysis and complex formation of protonated 2-diethylaminoethyl-acetate with formate anion.

To rationalize and improve receptor selectivity of local anesthetics of the procaine type a dynamic two-center model of the pharmacon-receptor interaction is suggested. A quantum chemical study within the Perturbation Configuration Interaction using Localized Orbitals (PCILO) approximations is carried out to find indications for a conformational change of this flexible drug from its thermodynamically preferred conformation to its pharmacologically active one. For this purpose, the pharmacon-receptor interaction is simulated quantum chemically by the interaction of the local anesthetic model compound 2-diethylaminoethyl-acetate (acetylcaine) with the one-center receptor model formate anion and the two-center receptor model gamma-aminobutyric acid in its zwitterionic form. In the present study, the conformational behaviour of acetylcaine is investigated in detail, confirming this molecule to be an appropriate model for procaine. In its formate complex the preferred conformation of acetylcaine is still retained with regard to the torsional angle of the [OCCN] fragment. Artefacts of the in-vacuo condition of the calculation are discussed. In view of the proposed interaction model, the importance of the first interaction of acetylcaine with the anionic receptor site is found to be in the fixation of the local anesthetic at the receptor surface, due to the long-range character of this interaction. Furthermore, an increased polarity of the carbonyl group of acetylcaine due to this interaction may enhance the proposed second interaction with the receptor.

Anesthetics, Local↗
PubMed1984

Cells involved in autologous rosette formation in mice. I. Two different subpopulations of thymocytes regulating autologous rosette formation.

In the studies on mouse thymocyte subpopulations--non-glass-adherent (NAL) cortisone-sensitive (HCS), and glass-adherent (GAL) cortisone-resistant (HCR) thymocytes the existence of precursors for helper and suppressor cells of the autologous rosette formation was demonstrated. A proline-rich polypeptide (PRP), an immunoregulator induced differentiation of helper and suppressor cells from NAL and GAL cells, respectively. These cells elevate or inhibit formation of autologous rosette by thymocyte subpopulations in vitro. Helper activity was abolished by treatment with monoclonal anti-Lyt 1,1 antibodies and suppressor activity was totally inhibited after treatment with monoclonal anti-Lyt 2,1 antibodies.

Animals↗
PubMed1983

[Comparative analysis of the role of the secondary and primary somatosensory areas of the cortex in the formation of the somatic responses of the reticular formation of the medulla oblongata in the rat].

Evoked potentials and unit activity of the medullar reticular formation were investigated in unanesthetized, immobilized albino rats either under cooling or lesion of the cortical representation of one of stimulated forepaws. The local cooling (lesion) of the cortex area C2 changed the amplitude and time parameters of the reticular evoked potentials to electrically stimulated contralateral forepaw whose representation was affected. As compared with the effect of C1 inhibition, changes in the amplitude and time parameters were insignificant and were not more then 30% and 10 ms, respectively. There were more corticofugal influences from C1 than from C2, both in experiments with evoked potentials and in analysis of somatic responses of reticular neurons. Thus corticofugal control of the medullar reticular formation in albino rats implemented by neuronic mechanisms of somatosensory areas C2 and C1 is qualitatively and quantitatively different.

Animals↗
PubMed1991

Chorioallantoic placenta formation in the rat: II. Angiogenesis and maternal blood circulation in the mesometrial region of the implantation chamber prior to placenta formation.

Rat gestation sites were examined on days 7 through 9 of pregnancy by light microscopy and transmission and scanning electron microscopy to determine the extent of vascular modifications in the vicinity of the mesometrial part of the implantation chamber (mesometrial chamber). At a later time, the mesometrial chamber is, in conjunction with the uterine lumen, the site of chorioallantoic placenta formation. On day 7, in the vicinity of the mesometrial chamber, vessels derived from a subepithelial capillary plexus and venules draining the plexus were dilating. By early day 8, this network of thin-walled dilated vessels (sinusoids) was further enlarged and consisted primarily of hypertrophied endothelial cells with indistinct basal laminas. Sinusoids were frequently close to the mesometrial chamber's luminal surface which was devoid of epithelial cells but was lined by decidual cell processes and extracellular matrix. By late day 8, cytoplasmic projections of endothelial cells extended between healthy-appearing decidual cells and out onto the mesometrial chamber's luminal surface, and endothelial cells were sometimes found on the luminal surface indicating that endothelial cells were migrating. The presence of maternal blood cells in the mesometrial chamber lumen suggested that there was continuity between the chamber and blood-vessel lumens. On day 9, the mesometrial chamber was completely lined with hypertrophied endothelial cells, and sinusoid lumens were clearly continuous with the lumen of the mesometrial chamber. Mesometrial sinusoids and possibly the mesometrial chamber lumen were continuous with vessels in vicinity of the uterine lumen that were fed by mesometrial arterial vessels. Clearing of the mesometrial chamber lumen during perfusion fixation via the maternal vasculature indicated the patency of this luminal space and its confluence with mesometrial arterial vessels and sinusoids. The conceptus occupied an antimesometrial position in the implantation chamber on days 7 through 9, and it was not in direct contact with uterine tissues in the vicinity of the mesometrial chamber. These observations suggest that angiogenesis, not trophoblast invasion or decidual cell death, plays a major role in the opening of maternal vessels into the mesometrial chamber lumen before the formation of the chorioallantoic placenta.

Animals↗
PubMed1983

Thermal degradation of precursors and formation of flavour compounds during heating of cereal products. Part II. The formation and changes of volatile flavour compounds in thermally treated malt extracts at different temperature and pH1.

The effect of temperature and pH on the formation and changes of volatile flavour compounds in thermally treated malt extracts was studied. The dependence of thermal treatment parameters on organoleptic properties of the extracts was stated. Alkaline pH of the medium was found to promote the formation of the compounds yielding a caramel odour. The most desirable organoleptic characteristics were obtained at pH 4.0-5.5 and temperature 140 degrees C. Thirty compounds typical for nonenzymatic browning were identified.

Chromatography, Gas↗