Levels of tropinone-reductase activities influence the spectrum of tropane esters found in transformed root cultures of Datura stramonium L.

The nortropane sulphur analogues 8-thiabicyclo[3.2.1] octan-3-one, 8-thiabicyclo[3.2.1]octan-3a-ol and 8-thiabicyclo[3.2.1]octan-3-ol have been found to have differential effects in vitro on the activities of tropinone reductase I and tropinone reductase II from Datura stramonium L. It has been demonstrated that only tropinone reductase I is able to metabolise 8-thiabicyclo[3.2.1]octan-3-one and that only this enzyme is inhibited by 8-thiabicyclo[3.2.1]octan-3-ol and 8-thiabicyclo[3.2.1]octan-3-ol. A K _m of 0.035 mM was determined for 8-thiabicyclo[3.2.1]octan-3-one and I₅₀ values of 0.081 mM and 0.021 mM for 8-thiabicyclo[3.2.1]octan-3-ol and 8-thiabicyclo[3.2.1]octan-3-ol, respectively. The influence that these differential interactions might have on metabolism was investigated in transformed root cultures of D. stramonium. It was found that when these cultures were grown in the presence of either 8-thiabicyclo[3.2.1]octan-3-one or 8-thiabicyclo[3.2.1]octan-3-ol the spectrum of alkaloids that accumulated was altered from that found in control roots in the manner predicted from the observed effects of these inhibitors on the isolated reductases. The effect could be mimicked by feeding pseudotropine, the product of tropinone reductase II. It is concluded that the relative levels of activity of the two tropinone reductases might play an important role in regulating the balance of tropan-3-ols to tropan-3-ols seen in the spectrum of tropane-alkaloid-producing plants.Abbreviations GC/MS gas chromatography/mass spectrometry; - I₅₀ concentration of inhibitor required to reduce the rate of reaction to half the maximal value; - -TBOL 8-thiabicyclo[3.2.1]octan-3-ol; - -TBOL 8-thiabicyclo[3.2.1]octan-3-ol; - TBON 8-thiabicyclo[3.2.1]octan-3-one; - TR tropinone reductase We are most grateful to J. Eagles (I.F.R., Norwich) for GC/MS analysis, to colleagues at I.P.B.P. and I.F.R. for helpful discussions, to the technical staff (Chemistry, Glasgow) and to W. Millar (Chemistry, Glasgow) for assistance with the reduction of TBON. This work was, in part, supported by a grant to B Dräger from the Deutsche Forschungsgemeinschaft (Dr227/I-I). The research reported here was supported by an Academic Research Collaboration Cooperative Award (project No. 215) from the British Council and the Deutscher Akademischer Austauschdienst to R.J. Robins and B. Dräger.     

Neuropeptide Y modulates the action of vasodilator agents in guinea-pig epicardial coronary arteries

Recently, we have demonstrated that guinea-pig epicardial coronary arteries are supplied by numerous nerve fibres containing neuropeptide Y (NPY) immunoreactivity. However, examination of vasomotor responses revealed that NPY did not elicit a contractile response in these arteries. In contrast, acetylcholine (ACh), calcitonin gene-related peptide (CGRP), substance P and vasoactive intestinal polypeptide (VIP) all relaxed precontracted arteries. In the present study, we have used histochemical, immunohistochemical and in vitro pharmacological techniques, in order to further investigate the possible role of NPY in guinea-pig epicardial coronary arteries. A double-immunofluorescence staining technique revealed that CGRP and substance P were co-localized in nerve fibres distinct from those displaying NPY immunoreactivity. Furthermore, using a method combining immunofluorescence and histochemical techniques, we observed that putative cholinergic nerve fibres (identified by their acetylcholinesterase content) and NPY-immunoreactive nerve fibres are two different nerve populations. An in vitro pharmacological method demonstrated that NPY markedly inhibited the relaxant responses mediated by ACh, VIP, substance P and isoprenaline but had no effect on CGRP. These results suggest that NPY-containing nerves associated with guinea-pig epicardial coronary arteries may be predominantly involved in modulating the action of vasodilator agents.     

1986 Survey of genetic toxicology testing in industry,government contract,and academic laboratories

Results of the 1986 Genetic Toxicology Association's survey of industrial, government, contract, and academic laboratories on the status of several assays in genetic toxicology are presented below. 1. The most commonly used assay was the Salmonella typhimurium/mammalian microsomal (Ames) assay, which was used by 83% of all respondents. 2. The next five (5) most commonly used assays were in vitro cytogenetics (72%), in vivo cytogenetics (59%), CHO HGPRT gene mutation (55%), the micronucleus assay (53%), and L517BY gene mutation (45%). 3. The assay showing the greatest percentage increase in routine use was the micronucleus assay which went from 14% in 1984 to 34% in 1986, an increase of 20%. 4. Other assays which increased in routine use were CHO HGPRT mutation (+18%); in vitro cytogenetics (+14%); L5178Y gene mutation (+9%), and the Ames assay (+5%). 5. Routine use of in vitro UDS assays declined by 6%; use of in vitro SCE assays declined by 12%. 6. There was no change in the rate of routine use of in vivo cytogenetics or in vivo SCE assays. 7. Assays routinely performed on contract included the Salmonella assay, CHO HGPRT gene mutation, in vitro cytogenetics, in vitro UDS, in vivo cytogenetics, the micronucleus assay, L5178Y gene mutation, and the Drosophila sex-linked recessive lethal assay. 8. Four assays were being developed by five or more laboratories. These included in vitro SCE (8); the micronucleus assay (7); in vivo SCE (6); and DNA adduct formation (5). 9. A total of 17 assays had been abandoned by one or more laboratories. However, since no assay had been given up by more than three laboratories no conclusions can be drawn about the overall robustness of any of the assays on the survey form.     

Aminoimidazole carboxamide ribonucleoside toxicity: a model for study of pyrimidine starvation

Aminoimidazole carboxamide ribonucleoside (AIC-R), a purine precursor, has biphasic effects on the growth of Chinese hamster fibroblasts. At 200 microM AIC-R cell growth is almost completely arrested, while at 50 and 700 microM AIC-R cell growth is comparable to that observed in the absence of nucleoside. The growth inhibition produced by AIC-R is the consequence of inhibition of the orotate phosphoribosyltransferase-orotidylic decarboxylase (OPRT-ODC) reactions, as evidenced by a 87% reduction in the intracellular concentrations of UTP and CTP, accumulation of orotate in the medium, and restoration of normal growth by inclusion of 100 microM uridine in the medium. Inhibition of pyrimidine nucleotide synthesis at 200 microM AIC-R is associated with an 82% reduction in the intracellular concentration of PP-ribose-P and a 150% increase in the concentration of purine nucleotides. Restoration of cell growth to a normal rate at 700 microM AIC-R--a condition under which PP-ribose-P remains depressed and purine nucleotide concentrations are also depressed (40% of control)--and absence of toxicity at 50 microM AIC-R--a condition under which purine nucleotide concentrations are increased by 150% and PP-ribose-P concentration is normal--suggest that the inhibition of OPRT-ODC observed at 200 microM AIC-R is caused by the combination of the reduction in PP-ribose-P and increase in purine nucleotides. These studies provide a better understanding of the control of the OPRT-ODC reactions in the cell and provide additional insight into the basis of pyrimidine starvation induced by purine nucleosides.     

Epidermal growth factor initiates DNA synthesis after a time-dependent sequence of regulatory events in Swiss 3T3 cells—interactions with hormones and growth factors

Epidermal growth factor (EGF) stimulates the initiation of DNA synthesis in Swiss 3T3 cells after a constant prereplicative period of 14–15 hours. The final rate of initiation follows apparent first-order kinetics and can thus be quantified by a rate constant k. The value of k can be changed by later additions during the prereplicative period: When cells stimulated by a very low concentration of EGF, alone or with insulin, which results in a relatively low value of k, receive a saturating amount of EGF at 15 hours, then k is markedly increased after 4–6 hours. Insulin alone (up to 200 ng/ml) is unable to set the lag phase, but does have a synergistic effect on the value of k given by EGF. When added at 15 hours, insulin also increases k, but after a delay of 4–6 hours. In contrast, both hydrocortisone and prostaglandin E₁ (PGE₁) inhibit the stimulation of DNA synthesis by EGF only during the first 8 hours of the prereplicative period of decreasing the value of k. Prostaglandin F_2α (PGF_2α), which stimulates DNA synthesis in a similar mode as EGF, when added with EGF has a synergistic effect on DNA synthesis. This suggests that EGF and PGF_2α, nevertheless, act through different regulatory events.     

Monoclonal antibody directed against RNA polymerase II of Drosophila melanogaster

Summary Monoclonal antibodies were raised against purified RNA polymerase II (or B) from Drosophila melanogaster. The antibody produced by one hybridoma cell clone was found to be directed against the two large subunits of the enzyme. The absence of antibodies directed against proteins possibly contaminating the antigens used for immunization allowed us to identify RNA polymerase unequivocally in interbands and puffs of polytene chromosomes. Within a single heat shock puff (87C1) RNA polymerase was found to be clustered in two separate areas suggesting two distint regions of RNA polymerase activity in this puff.Abbreviations FITC fluorescein isothiocyanate - PAGE polyacrylamide gel electrophoresis - PBS phosphate buffered saline - SDS sodium dodecyl sulfate - Enzyme DNA-dependent RNA polymerase or nucleotide-triphosphate - RNA nucleotidyltransferase (EC 2.7.7.6)     

Trypanosoma cruzi: defined medium for continuous cultivation of virulent parasites.

A liquid medium was developed for the continuous cultivation of Trypanosoma cruzi. Among the several highly purified macromolecules tested only bovine liver catalase, horseradish peroxidase, lactoperoxidase, and bovine hemoglobin supported the continuous growth, at high yield, of mice-virulent Trypanosoma cruzi; other hemoproteins were inactive. Bovine liver catalase showed optimal Trypanosoma cruzi growth-promoting activity, parasites reaching 20 × 10⁶ parasites/ml (95% epimastigotes) at about 10 days in most of the 45 subpassages to date. Furthermore, this protein in the incubation medium provided all the amino acid requirements of actively growing parasites, thus eliminating the need for exogeneous free amino acids. Additional experiments revealed that the hemoprotein's growth-promoting activity was independent of any enzymatic activity and that reconstituting the exact protein composition by means of exogeneous amino acids did not support parasite multiplication, suggesting the importance of the primary structure of the active proteins for growth-promoting activity. These active macromolecules supported the multiplication of five different strains of Trypanosoma cruzi, but did not support Leishmania brasiliensis or Leishmania mexicana proliferation, suggesting species specificity.     

Characteristics affecting fibrinolytic activity and plasma fibrinogen concentrations.

As part of a study to determine the extent to which the haemostatic system is implicated in the onset of clinically manifest ischaemic heart disease, characteristics influencing fibrinolytic activity (FA) and plasma fibrinogen concentrations were examined in 1601 men aged 18-64 and 707 women aged 18-59 in several occupational groups in North-west London. In men FA noticeably decreased till the age of about 58, when there was a small rise. In women a small increase in FA between 18 and about 40 was followed by a slightly larger fall between 40 and 59. There was a pronounced negative association of FA with obesity. FA was significantly less in smokers than non-smokers, though the effect was not large. FA increased with alcohol consumption. FA in men appeared to be greatest in the lower social classes, and men on night shift had poorer FA than those on day work. FA was greater in women using oral contraceptives than in those not using these preparations. In both sexes FA increased with exercise, but there were no associations between any of the characteristics studied and the increase. Plasma fibrinogen concentrations increase with age and obesity, are higher in smokers than non-smokers, and fall with alcohol consumption. In women the concentrations are higher in those using oral contraceptives. The general epidemiology of FA and plasma fibrinogen concentrations suggests that they may well be implicated in the pathogenesis of ischaemic heart disease.     

Structural investigation of the capsular polysaccharide of Klebsiella serotype k23

Klebsiella K23 capsular polysaccharide has been investigated by the techniques of hydrolysis, methylation, Smith degradation-periodate oxidation, and base-catalysed degradation, either on the original or the carboxyl-reduced polysaccharide. The structure was found to consist of a tetrasaccharide repeating-unit, as shown below. The anomeric configurations of the sugar residues were determined by ₁H-and ¹³C-n.m.r. spectroscopy on the original and degraded polysaccharides.

     

Synthesis of nerve growth factor in rat glioma cells

We have analyzed the incorporation of radioactive amino acids by rat C6 glioma cells into material precipitable with anti-β-nerve growth factor (NGF). We show that amino acids are incorporated into a protein the size of β-NGF which is immunologically related to NGF and which has peptides similar to those of mouse β-NGF. Several lines of evidence obtained in this study support the hypothesis that NGF is produced by the proteolytic cleavage of a higher molecular weight precursor. This evidence includes kinetic studies, demonstration of higher molecular weight material (24,000) immunologically related to NGF, and in vitro processing of the 24,000 MW protein to material of the approximate size of β-NGF.