Comments on the report of 'association' of omeprazole with DNA by Phillips et al.
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Animals↗
Biomedical subjects
S M Galloway
Publications and source records attributed to S M Galloway.
International Commission for Protection Against Environmental Mutagens and Carcinogens. Genotoxicity under extreme culture conditions. A report from ICPEMC Task Group 9.
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Animals↗
A mutant of Escherichia coli defective in the first step of endotoxin biosynthesis.
Using localized mutagenesis of whole cells, we have isolated a temperature-sensitive UDP-N-acetylglucosamine acyltransferase mutant of Escherichia coli that loses all detectable acyltransferase activity and quickly dies after a shift from 30 to 42 degrees C. Acyltransferase activity and temperature resistance are restored by transforming the mutant with a hybrid plasmid containing the E. coli gene for UDP-GlcNAc acyltransferase (lpxA). In addition, a new assay has been developed for quantitating the amount of lipid A (the active component of endotoxin) in E. coli and related Gram-negative strains. Cells are labeled with 32Pi and extracted with chloroform/methanol/water (1:2:0.8, v/v) to remove glycerophospholipids. The residue is then hydrolyzed with 0.2 M HCl to liberate the "monophosphoryl" lipid A degradation products (Qureshi, N., Cotter, R. J. and Takayama, K. (1986) J. Microbiol. Methods 5, 65-77), each of which bears a single phosphate residue at position 4'. The amount of lipid A is normalized to the total amount of labeled glycerophospholipid present in the cells. The steady state ratio of lipid A to glycerophospholipid in wild-type cells is approximately 0.12. The lipid A content of the acyltransferase mutant is reduced 2-3-fold, and the rate of lipid A synthesis is reduced 10-fold when compared to wild-type after 60 min at 42 degrees C. These results provide physiological evidence that UDP-N-acetylglucosamine acyltransferase is the major committed step for lipid A biosynthesis in E. coli and that lipid A is an essential molecule.
Acyltransferases↗
Isolation and structural characterization of insulin and glucagon from the holocephalan species Callorhynchus milii (elephantfish).
Both insulin and glucagon from the pancreas of the holocephalan cartilaginous fish Callorhynchus milii (elephantfish) have been isolated and purified. Two reverse-phase h.p.l.c. steps enabled recovery of sufficient material for gas-phase sequencing of the intact chains as well as peptide digestion products. The elephantfish insulin sequence shows 14 differences from pig insulin, including two unusual substitutions, Val-A14 and Gln-B30, though none of these is thought likely to influence receptor binding significantly. The insulin B-chain contains 31 residues, one more than mammalian insulins, but markedly less than that of the closely related ratfish with which it otherwise exhibits high sequence similarity. Elephantfish and pig glucagons differ at only four positions, but there are six changes from the ratfish glucagon-36 (normal glucagon contains 29 residues) sequence. It is apparent that different prohormone proteolytic processing mechanisms operate in the two holocephalan species.
Amino Acid Sequence↗
Insulin-like material from the digestive tract of the tunicate Pyura pachydermatina (sea tulip).
Gut tissue from the tunicate Pyura pachydermatina (sea tulip) was found to contain a compound or compounds which react with anti-porcine insulin antibodies, but not anti-hag-fish insulin antibodies, and which also stimulate lipogenesis in isolated rat fat cells. The insulin-like material is present in two immunologically active forms, a species of Mr 6000 apparently similar to mammalian insulin, and a high Mr form which expresses biological activity only after further purification by reverse-phase HPLC. The bioactivity of both species is suppressed in the presence of anti-porcine insulin antibodies.
Adipose Tissue↗
Repair of sister-chromatid exchange-inducing lesions in mutagen-treated cultures of human whole blood and purified fresh or frozen lymphocytes.
Repair of mutagen-induced lesions that result in sister-chromatid exchanges was evaluated in 10 normal individuals. The mutagens used were mitomycin C (MMC), 4-nitroquinoline 1-oxide (4NQO), and N-methyl-N'nitro-N-nitrosoguanidine (MNNG). Cultures of whole blood, freshly purified lymphocytes, or purified lymphocytes cryopreserved for 6 months were analyzed after the mutagen treatments. All 3 mutagens induced reparable damage as evaluated by comparison of sister-chromatid exchanges between cultures that were given time to repair induced damage before 5-bromo-2'-deoxyuridine (BrdUrd) was added to the culture medium with those where BrdUrd was added immediately after the administration of the mutagens (MMC or 4NQO) or at culture initiation (MNNG). Repair of mutagen-induced DNA damage was detected in all 3 culture types; thus cryopreservation did not appear to alter the capacity of lymphocytes to repair mutagen-induced lesions. Quantitative differences in apparent repair capabilities were observed among individuals. Variability also existed among the different culture types within an individual, suggesting that caution should be exercised in interpreting these apparent differences.
4-Nitroquinoline-1-oxide↗
Gram-negative endotoxin: a biologically active lipid.
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Animals↗
The effects of a new beta-adrenoceptor agonist BRL 26830A in refractory obesity.
Beta-adrenoceptor agonists have recently been shown to promote substantial loss of adipose tissue in laboratory animals. One of these BRL, 26830A, increases thermogenesis in human volunteers and has been shown to enhance the rate of weight reduction in patients adhering to a strict reducing regimen. Forty-three post-menopausal or sterilized female subjects suffering from refractory obesity participated in a double-blind placebo-controlled study, the treatment group receiving BRL 26830A 50 mg qid. Two subjects were withdrawn because they developed an unpleasant sensation of tremor and in all, 17 of the 20 who received BRL 26830A mentioned this side effect. There was no change in erect or supine blood pressure or in resting heart rate. There was no significant difference in weight change during the 6-week study. It is concluded that BRL 26830A does not appear to promote weight reduction in subjects unable to adhere strictly to their dietary regime.
Adrenergic beta-Agonists↗
Chromosome aberrations and sister chromatid exchanges in Chinese hamster ovary cells: evaluations of 108 chemicals.
Results from the testing of 108 coded chemicals in Chinese hamster ovary (CHO) cells for the induction of chromosome aberrations and sister chromatid exchanges (SCEs) are presented. All chemicals were tested with and without exogenous metabolic activation, using protocols designed to allow testing up to toxic doses. Cell harvest times could also be extended if chemical-induced cell cycle delay was seen. Chromosome aberrations were induced by 43 of the chemicals, and 66 induced SCEs; 37 of the chemicals were positive for both endpoints.
Animals↗
Baseline and mutagen-induced sister-chromatid exchanges in cultures of human whole blood and purified fresh or frozen lymphocytes.
Baseline and mutagen-induced levels of sister-chromatid exchanges were evaluated in 10 normal individuals. Cultures with whole blood or purified lymphocytes, either freshly isolated or after 1 or 6 months of cryopreservation, were analyzed to determine whether frozen lymphocytes are suitable for SCE studies. Whole blood and freshly isolated lymphocytes were cultured from samples taken at the beginning of the study (Time 0) and 6 months later (Time 6). Cryopreserved lymphocytes were recovered after 1 month (Time 1) and 6 months (Time 6) of cryopreservation and then challenged with mutagens in culture. The mutagens used were mitomycin C, 4-nitroquinoline-1-oxide, and N-methyl-N'-nitro-N-nitrosoguanidine. Purified lymphocytes had consistently and significantly higher baseline SCE frequencies than cells from whole blood cultures and were more sensitive to N-methyl-N'-nitro-N-nitrosoguanidine and 4-nitroquinoline-1-oxide. The response to mitomycin C was similar in all culture types. There was, overall, no consistent effect of freezing on baseline or induced sister-chromatid exchange frequencies in the purified lymphocytes. This suggests that purification and cryopreservation of human lymphocytes does not alter the baseline or mutagen-induced sister-chromatid exchange response and in certain epidemiological, occupational and monitoring situations may have logistical and technical advantages over the use of fresh whole blood.
4-Nitroquinoline-1-oxide↗
Effects of high osmotic strength on chromosome aberrations, sister-chromatid exchanges and DNA strand breaks, and the relation to toxicity.
Substantial increases in chromosome aberrations were induced in Chinese hamster ovary cells by medium made hyperosmotic with NaCl, KCl, sucrose, sorbitol or dimethyl methylphosphonate. The increases were associated with cytotoxicity but occurred in the range (e.g., 70% survival) commonly included in in vitro tests for 'genotoxicity'. The relation between increased osmotic pressure and chromosome aberrations is compound-dependent, e.g., some compounds may have a direct effect in addition to an effect mediated by osmotic pressure/ionic strength. Also, glycerol at high osmolality was not toxic and did not induce aberrations, probably because rapid equilibration across the cell membrane precluded severe osmotic stress to the cells. Weak increases in DNA single-strand breaks (NaCl and KCl) and double-strand breaks (NaCl) were also detectable, at higher concentrations and more toxic levels than those required to produce aberrations. Slight elevations in sister-chromatid exchange frequencies caused by hyperosmotic medium were found in the presence of toxicity and severe cell cycle delay. Our data on cell growth inhibition suggest that this is the result of increased incorporation of bromodeoxyuridine per cell due to decreased numbers of growing cells, although other mechanisms cannot be ruled out. The observations on chromosome aberrations demonstrate the need for keeping in vitro test conditions in the physiological range, and provide a means for investigation of indirect DNA damage.
Animals↗
Relationships among cytotoxicity, lysosomal breakdown, chromosome aberrations, and DNA double-strand breaks.
Certain chemicals that are either weak or non-carcinogens had been previously shown to induce DNA single-strand breaks in rat hepatocytes, but only at cytotoxic doses. In contrast, stronger carcinogens induced DNA single-strand breaks at non-toxic doses. This report shows that the strong carcinogens and mutagens cadmium sulfate, sodium dichromate, dimethyl sulfate, and N-methyl-N'-nitro-N-nitrosoguanidine all induce DNA single-strand breaks at non-toxic concentrations, but that they also induce DNA double-strand breaks at concentrations that are closely correlated with cytotoxicity. Some weak carcinogens produced DNA single- and double-strand breaks, but only at acutely cytotoxic concentrations. We suggest that the DNA double-strand breaks result from a cell-mediated process such as release of DNAase from lysosomes or other cellular compartments, that might occur during cellular response to acutely toxic damage. Experiments with N-dodecyl imidazole (NDI), a lysosomal detergent, show that lysosomal breakdown alone is only a weak inducer of DSBs, but that lysosomal breakdown in combination with prior chemical damage produced by MNNG synergistically induces DNA DSBs in BHK cells. N-Dodecyl imidazole also induces chromosomal aberrations in CHO cells at concentrations which cause cytotoxicity, cell cycle delay, and lysosomal breakdown. These results all suggest that chemical toxicity leads to limited lysosomal breakdown that induces DNA DSBs and chromosomal aberrations. Cells that have been sublethally damaged and that can repair these damages and survive could become transformed by the DNA-damaging mechanisms associated with carcinogenesis.
Animals↗
Statistical analyses for in vitro cytogenetic assays using Chinese hamster ovary cells.
It is a widely held view that objective statistical criteria are needed for the evaluation of genetic toxicity assays. This paper presents statistical methods for the analysis of data from in vitro sister chromatid exchange (SCE) and chromosome aberration tests that use Chinese hamster ovary cells. For SCEs, an extensive study of solvent control results demonstrated that there is a substantial interday component of variability in the data, and that a Poisson sampling model is applicable to data generated via the protocol of Galloway et al [1985]. Consequently, a trend test for evidence of a dose response is proposed for such SCE data. As an illustration of this statistical method, analysis of data previously considered to be negative [Gulati et al, 1985] indicates that di(2-ethyl-hexyl) phthalate induces a weak, but reproducible, SCE dose response in CHO cells. Monte Carlo methods are used to show that the trend test is more sensitive than four other statistical procedures considered for the analysis of Poisson-distributed SCEs. A similar trend test for dose response in proportions is proposed for chromosome aberration data, where the percent of cells with chromosome aberrations is the response of interest. Sensitivity (or power) studies indicate that three doses and a control with 50 cells/dose point is a reasonable design for an in vitro SCE study that uses the Galloway et al protocol. For in vitro chromosome aberrations, however, three doses and a control with 100 cells/dose point appears to produce too insensitive an assay; an increase to 200 cells/dose point in the Galloway et al protocol seems worthy of serious consideration.
Animals↗
Placebo controlled double-blind trial of fluvoxamine maleate in the obese.
Obesity and depression are common disorders which may co-exist. The management of the combination is complicated because some antidepressants cause weight gain fenfluramine, an effective antiobesity agent, may cause depression. Fluvoxamine is an antidepressant which, like fenfluramine, inhibits serotonin re-uptake within the brain. Forty obese female subjects with refractory obesity participated in a double-blind placebo controlled trial. During the twelve week study, those subjects receiving fluvoxamine achieved a mean weight loss greater than, but not significantly different from, that of the placebo group. The result suggests that fluvoxamine may be particularly useful in the management of obese patients requiring treatment with an antidepressant.
Adolescent↗
Intermittent protein-sparing fasting with abdominal belting.
In an attempt to minimize the weight regain that often follows effective weight reduction, a programme has been evaluated which involved the use of a nylon waist cord which could be readily tightened but not lengthened, during a regime of alternating periods of a liquid diet and a high-fibre natural diet combined with behavioural modification. Forty subjects completed the initial cycle of a liquid regime with an overall weight loss of 7.7 kg during the treatment period. Thirty-six of these subjects have been followed up for a mean of 12 months after the completion of the treatment programme. Five subjects are difficult to categorize having worn the cord for some but not all of this time. Fourteen have continued to wear the waist cord throughout and have achieved a further mean weight loss of 4.8 kg. This differs significantly from the 17 subjects who cut off the cord and who have regained a mean of 6.6 kg. The results suggest that an adjustable waist cord is a valuable aid to achieving successful and permanent weight reduction in some subjects.
Adult↗
Development of a standard protocol for in vitro cytogenetic testing with Chinese hamster ovary cells: comparison of results for 22 compounds in two laboratories.
A major problem of cytogenetics testing in mammalian cells is lack of agreement of results among laboratories. Our objective was to develop a sensitive in vitro test protocol that was applicable to large-scale chemical screening and yielded comparable results in two laboratories. We used sister chromatid exchange (SCE) and chromosome aberration (CAb) tests in Chinese hamster ovary (CHO) cells. The initial protocol used standard cell densities, medium, batch of rat liver S9 for metabolic activation; positive, negative, and solvent controls; staining and scoring techniques; and fixation times. Treatment without S9 was for 8-12 hr (CAb) or 26 hr (SCE), and with S9 for 2 hr in serum-free medium. Bromodeoxyuridine (BrdUrd) (10 microM) was added to SCE cultures only, 2 hr after addition of the test chemical. Doses were based on the 50% toxicity level in a preliminary test of cell survival 24 hr after treatment. One hundred cells (CAb) or 50 cells (SCE) were scored from each control and from five dose levels. Five clastogens were tested in the first two-laboratory comparison: mitomycin-C, triethylenemelamine, N-methyl-N'-nitro-N-nitrosoguanidine, cyclophosphamide, and benzo(alpha)pyrene. There was quite good agreement between laboratories. Seventeen compounds were then tested "blind" in the two laboratories. As testing proceeded, some discrepancies occurred between the laboratories, and the protocol was modified in attempts to improve the resolution of marginal responses and make dose selection more consistent. The preliminary test for cell survival was omitted. A 10(5) dose range in a half-log series was tested, and cells were scored at the highest dose at which sufficient mitotic cells were obtained, and at the next two lower doses. By delaying fixation times, SCE and CAb were scored at doses that inhibited cell cycle progression. This protocol gave comparable results in the two laboratories in many cases and by testing up to a maximum dose, limited by solubility and/or toxicity, should detect a high proportion of clastogens and SCE inducers.
Animals↗
Cytochrome P-450 metabolic activity in embryonic and extraembryonic tissue lineages of mouse embryos.
Mouse morulae, blastocysts, and embryonic and extraembryonic tissue layers were examined for benzo[a]-pyrene metabolism by cytochrome P-450, using the sister chromatid exchange assay. Benzo[a]pyrene exposure in vitro increased sister chromatid exchanges in blastocysts of all genetically responsive mice examined [BALB/cDub, C3H/AnfCum, and outbred Dub:(ICR) strains] but not blastocysts of the nonresponsive AKR/J strain. Benzo[a]pyrene treatment of responsive 7 1/2- and 8 1/2-day (postimplantation-stage) embryos, either intact or as separate tissue layers, increased sister chromatid exchanges in tissues of both embryonic and extraembryonic lineages--i.e., in the embryo proper, in isolated embryonic ectoderm, and in yolk sac, chorion, extraembryonic ectoderm, and extraembryonic endoderm layers. These results indicate that cytochrome P-450 is active in most or all tissues of the early mammalian embryo. It could metabolize xenobiotic molecules reaching the conceptus near the onset of morphogenesis and organogenesis, or it could have another as yet undefined role in normal development.
Age Factors↗
Sister-chromatid exchange (SCE) report on control subjects in a study of occupationally exposed workers.
The range and distribution of Sister-Chromatid Exchange (SCE) scores in 479 control persons were determined. All SCE readings were performed in a single laboratory according to the same protocol and regularly checked by referee readers to assure consistency. A mean SCE per cell value of 9.9 and a 95th percentile of 13.4 were established for this study sample. The range of SCE scores across all non-exposed individuals tested was 5.0-17.5 SCE per cell. Differences in SCE scores were associated with reader, smoking, sex, and, to a small extent, age. Individual test results showed reasonable consistency across the entire control group, but, as with most clinical measurements, care should be taken to avoid placing too much emphasis on a single test result when communicating with an individual. This report on the largest control group studied to date provides necessary normative data for further SCE investigations in occupational settings.
Adult↗