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B J Phillips

Publications and source records attributed to B J Phillips.

At least 19 recordsLinked to original sources
PubMed1995

Induction of polyploidy in human lymphocytes in vitro by excess adenine, but not by adenosine.

It is known that high levels of DNA precursors can be both clastogenic and mutagenic in cultured cell lines and in vivo. The purpose of the present study was to examine at an observational level the cytogenetic effects of adenine and adenosine in primary human cell cultures. Human peripheral blood lymphocytes from four donors were cultured and treated with a range of concentrations of adenine and adenosine. Although no increase in sister chromatid exchange (SCE) frequency was observed with either compound, there was a statistically significant, dose-related increase in the proportion of polyploid cells in cultures treated with adenine, but not in those treated with adenosine. Some of the polyploid metaphases found after adenine treatment contained diplochromosomes, suggesting that endoreduplication might have been involved in polyploid formation in these cells. It is concluded that a high level of adenine can cause genetic changes in human lymphocytes by interfering with mitosis, perhaps by disturbing the balance of DNA precursor pools.

Adenine↗
PubMed1994

The effect of various antioxidants and other modifying agents on oxygen-radical-generated DNA damage in human lymphocytes in the COMET assay.

The effects of antioxidants and various other modifying agents on oxygen-radical-generated DNA damage in human lymphocytes have been investigated using the COMET assay. Hydrogen peroxide (H2O2) and bleomycin (BLM) have produced clear dose-related responses. In 38 independent experiments, there was consistency between the two donors used in the study for the negative and positive control data. The endogenous antioxidant catalase abolished effects with H2O2, but only slightly affected the response with BLM. Superoxide dismutase did not alter the response with H2O2 and only slightly affected BLM. The exogenous antioxidant vitamin C produced a clear dose-related response on its own. In combination with H2O2, there were small protective effects at low doses and exacerbating effects at high doses, but these were within the inter-experimental variability range. Vitamin E (trolox) produced no effects with either H2O2 or BLM, or on its own. Silymarin protected against the effect due to H2O2. Other modifying agents such as apo-transferrin and deferoxamine mesylate produced a clear dose-related protection of effects due to BLM. This protection was less due to H2O2. In the presence of ferrous chloride, the effect due to BLM was exacerbated. In a small sample of 6 smokers and 6 non-smokers, responses from smokers approached borderline significance (P = 0.054) by comparison with non-smokers. These observations would suggest that the COMET assay is a useful tool for examining issues related to oxidative stress in human lymphocytes.

Adult↗
PubMed1993

Molecular analysis of mutations at the tk locus of L5178Y mouse-lymphoma cells induced by ethyl methanesulphonate and mitomycin C.

Mutations at the tk locus of mouse-lymphoma L5178Y cells were induced by treatment with ethyl methanesulphonate (EMS), primarily a point mutagen and mitomycin C (MMC), a potent clastogen. Mutant colony size was distinctly bimodal with 35% of spontaneous mutants growing as small colonies and 65% large. The proportion of small colonies increased only slightly to 41% in EMS-treated cultures but to 64% after MMC treatment. Mutations were analysed by Southern and Northern blotting. Digestion of DNA with the restriction enzyme, Nco I, revealed that many mutants had lost a 6.3-kb fragment which constituted the loss of the entire tk gene. Almost all of the EMS-induced large-colony mutants analysed (9/10) retained the tk+ allele suggesting the presence of an intragenic mutation. Of the small-colony mutants, half (6/12) had lost the tk+ gene and presumably other genes affecting growth and half retained the tk+ allele suggesting point mutations in both the tk gene and other sites in the genome affecting growth. A very different spectrum of mutation was induced with MMC. Only 1/12 of the large-colony mutants were due to intragenic mutation, the remaining large-colony mutants having lost the tk+ allele while all the small-colony mutants had lost the tk+ gene presumably with the deletion extending to genes essential for normal growth. Northern blot analysis showed no changes in the size of tk transcript in any mutants. Alterations in the amount of tk mRNA were not detectable since all mutants produced an mRNA of similar size and amount, which may indicate the production of an abnormal mRNA from the tk- allele. Unlike cell-mutation assays that use hemizygous loci (such as hprt+/0) for detecting potential chemical carcinogens, the mouse-lymphoma tk+/- assay allows the recovery of both intragenic and intergenic mutations thus enabling the detection of both point mutagens such as EMS and potent clastogens like MMC.

Animals↗
PubMed1993

Molecular analysis of mutation at the hprt locus of Chinese hamster V79 cells induced by ethyl methanesulphonate and mitomycin C.

Mutations at the hprt locus of Chinese hamster V79 cells were induced by treatment with ethyl methanesulphonate (EMS), considered primarily a point mutagen and mitomycin C (MMC), a potent clastogen. EMS gave a dose-dependent induction of mutants while MMC induced a poor mutagenic response. Mutations were analysed using Southern and Northern blotting. Analysis of 9 EMS-induced and 4 spontaneous mutants yielded no detectable alterations in the hprt locus after digestion of DNA with 6 restriction enzymes. Mutants without detectable changes carried presumptive point mutations. In contrast, 4 out of 12 MMC-induced mutants had detectable alterations. 2 of these appeared to have lost the entire hprt gene while the other 2 had probable partial deletions. For these 4 deletion mutants no hprt mRNA was detected. 3 MMC-induced and 1 EMS-induced mutants had reduced levels of hprt mRNA. All the other mutants showed normal levels of hprt mRNA and the message detected was always of the correct size. It is suggested that the poor mutagenic response induced by MMC may be due to the lethal nature of large deletions involving both the hemizygous hprt locus and adjacent essential genes. This may lead to an underestimate of the mutagenicity of clastogenic agents such as MMC in the V79 HPRT mutation assay.

Animals↗
PubMed1992

Use of mivacurium chloride by constant infusion in the anephric patient.

Twenty anephric and 20 healthy patients received a bolus dose of mivacurium 150 micrograms kg-1. When the first EMG response (T1) of the train-of-four had recovered to 5% of control (T0), an infusion of mivacurium 10 micrograms kg-1 min-1 was started and adjusted to keep T1 at 5%. Ten patients in each group were given neostigmine 35 micrograms kg-1 when the infusion was stopped when T1/T0 had recovered to 20%; in the others recovery was spontaneous. After the bolus dose of mivacurium, mean (SD) depression of T1 was greater in the anephric group than in the normal group (98.4 (3.5) vs 96.8 (4.4)%; P less than 0.01) and recovery of T1/T0 to 5% was slower (15.3 (6.9) vs 9.8 (3.5) min; P less than 0.01). Anephric patients required a slower infusion rate (6.3 (1.9) vs 10.4 (2.8) micrograms kg-1 min-1; P less than 0.001). Neostigmine hastened recovery of both T1/T0 and T4/T1 in both groups. Spontaneous recovery of T1/T0 (from 25% to 75%) after the infusion was also slower in anephric patients (12.2 (8.2) vs 7.7 (1.2) min; P less than 0.05). Plasma cholinesterase activity was less in the anephric group (785 (207) vs 943 (217) iu litre-1; P less than 0.05) and there was a (negative) correlation overall between cholinesterase activity and time to 5% recovery of T1/T0 after the bolus dose (r = -0.42; P less than 0.02). We conclude that patients with chronic renal failure may require a reduced dose of mivacurium.

Adult↗
PubMed1990

Effects of methyl isocyanate on rat brain cells in culture.

Since the disaster in Bhopal, India, people exposed to methyl isocyanate (MIC) have complained of various disorders including neuromuscular dysfunction. In an attempt to get information about such dysfunction we have previously shown that MIC can affect muscle cells in culture. The present communication reports investigations into the effect of MIC on brain cells in culture. MIC was toxic to brain cells and the response was dose related. The observations were supported by light and electron microscopy.

Animals↗
PubMed1990

Chinese hamster ovary (CHO/HPRT) cell mutation assays with EMS, benzo[a]pyrene and benzidine.

In the context of the third UKEMS collaborative trial on cell mutation assays, three chemicals have been tested for mutagenicity using the Chinese hamster ovary (CHO) cell/HPRT assay. The protocol employed was based on the re-spreading of monolayer cultures, maintaining one million cells in growth for an expression time of 7 days. Ethyl methanesulphonate gave clear and consistent positive results in the absence of S9 and a clear response to benzo[a]pyrene was obtained with 1% S9. Benzidine gave no evidence of mutagenicity either with or without S9. The results show that the CHO/HPRT assay protocol used in this study is adequate for the detection of potent mutagens. The failure to detect benzidine as a mutagen may be due either to a basic unresponsiveness of the system or to a lack of sensitivity because of the limitation on the numbers of cells which can be maintained during expression. Statistical analysis showed that significant variation occurred between cell survival and mutagenicity estimates for replicate cultures, demonstrating the need for duplicate cultures.

Animals↗
PubMed1989

Microsome-mediated clastogenicity of butylated hydroxyanisole (BHA) in cultured Chinese hamster ovary cells: the possible role of reactive oxygen species.

Butylated hydroxyanisole (BHA) was found to induce chromosome aberrations in Chinese hamster ovary (CHO) cells in the presence of Aroclor-induced rat-liver S9. The effects were more marked when washed microsomes were employed and chromosome damage was considerably reduced in the presence of catalase, suggesting that hydrogen peroxide was involved. Stimulation of H2O2 production by BHA in S9 or microsome incubation mixtures was demonstrated using the catalase-mediated production of formaldehyde from methanol. One of the major microsomal metabolites of BHA, tert.-butyl hydroquinone (t-BHQ), which autoxidises in solution producing H2O2 also induced extensive catalase-sensitive chromosome damage in the absence of metabolic activation. These observations suggest that extracellular generation of reactive oxygen species may be implicated in the mechanism of BHA clastogenicity in vitro. However, chromosome damage was not completely abolished by catalase and the end product of t-BHQ oxidation, tert.-butyl quinone, was also weakly clastogenic, suggesting that intracellular effects of quinone metabolites may also be involved in the clastogenicity of BHA.

Animals↗
PubMed1988

Effects of methyl isocyanate on rat muscle cells in culture.

Since the Bhopal disaster, in which the causal agent was methyl isocyanate (MIC), exposed people have complained of various disorders including neuromuscular dysfunction. In an attempt to gain some information about the response of muscle tissue to MIC its effects were investigated in cells in culture isolated from muscle of 2 day old rats. After treatment with a range of MIC concentrations (0.025-0.5 microliter/5 ml culture) the total number of nuclei of the two main cell types (fibroblasts and myoblasts) and the number of nuclei in muscle fibres (myotubes) were recorded. At lower doses which had little effect on the total number of nuclei, the formation of muscle fibres--that is, fusion of muscle cells--was prevented as the proportion of nuclei in myotubes was decreased. At higher doses both cell types were killed. This would suggest either an effect on muscle differentiation or a selective toxicity towards myoblasts. The observations were supported by light and electron microscopy.

Animals↗
PubMed1988

Studies of the 'adaptive' repair response in human lymphocytes and V79 cells after treatment with MNNG and MNU.

In bacteria, there is evidence that a damage inducible repair response system known as the adaptive response exists since pretreatment with low doses of a simple monofunctional alkylating agent leads to a decrease in both the lethal and mutagenic effects of a subsequent challenge dose of the agent. The evidence for an analogous system in mammalian cells has proved to be inconsistent to date. The induction of chromosome repair mechanisms in human cells by low-dose radiation from tritiated thymidine has been shown to make the cells refractory to the induction of chromosome aberrations by X-rays. The present communication investigates the induction of an adaptive response in human lymphocytes from four donors and V79 cells using SCE and mutation as endpoints and MNNG and MNU for the adapting and challenging treatment. It is clear that a reproducible model of the adaptive response in human lymphocytes is difficult to establish because of the variability between different donors and different culture times. In V79 cells, assays with much larger cell numbers are required to detect a reproducible response with such small changes in mutant frequency. To demonstrate an adaptive response conclusively in mammalian cells will probably require the use of more sensitive experimental protocols and alternative methods of administration of adaptive doses of mutagen.

Animals↗
PubMed1986

Mutagenic properties of N-nitrosopeptides in mammalian cell culture assays.

Two N-nitrosopeptides, N-(N-acetyl-L-prolyl)-N-nitrosoglycine and N-(N-acetylvalyl)-N-nitrosoglycine, were investigated for genetic toxicity towards mammalian cells using an established line of Chinese hamster ovary cells (CHO-K1-BH4). Observations were made on three indices of genetic damage, namely chromosome aberrations, sister chromatid exchange and induction of thioguanine-resistant variants. Treatment of cells with either compound resulted in dose-dependent increases in all indices, indicating that both compounds are direct-acting mutagens.

Animals↗
PubMed1986

Studies on the genetic effects of phthalic acid esters on cells in culture.

Mono(2-ethylhexyl) phthalate (MEHP) induced chromosome aberrations in cells of two culture lines, one derived from Chinese hamster ovary cells (CHO) and the other from rat liver cells (RL4). In CHO cells, the clastogenicity of MEHP was unaffected by the presence of an exogenous metabolic activation system (S-9 mix). 2-Ethylhexanol, o-phthalic acid, and phthalic anhydride were without effect. Cytochemical methods and assays for carnitine acetyltransferase and KCN-insensitive palmitoyl CoA oxidation were employed to determine whether chromosome damage was associated with peroxisome proliferation. No evidence of an increase in peroxisome numbers or of induction of marker enzymes was found in CHO cells treated with MEHP for up to 72 hr. Clofibric acid and BR931 were also ineffective. Observations on changes in CHO cell structure and permeability, and on the haemolytic effects of phthalate monoesters, suggest that the cytotoxicity of MEHP may be due primarily to its action on cell membranes. Since chromosome damage was observed only at cytotoxic concentrations, it is suggested that damage to lysosomal membranes and the release of endonucleases may be responsible for the observed clastogenicity of MEHP in vitro.

Animals↗
PubMed1985

Nitrofurazone--genotoxicity studies in mammalian cells in vitro and in vivo.

Nitrofurazone has been examined for genetic effects in mammalian cells in vitro and in vivo. In the in vitro studies in Chinese hamster ovary (CHO) cells, metaphase analysis was carried out at different sampling times after nitrofurazone treatment and gene mutation leading to hypoxanthine-guanine phosphoribosyltransferase deficiency was also investigated. Both assays were carried out in the presence and absence of a metabolic activation system (S-9 mix). Metaphase analysis was also carried out on bone-marrow cells at various sampling times after treatment of rats with a single oral dose of nitrofurazone and at one sampling time after administration of five daily oral doses. In the in vitro studies a dose-related increase in aberrant metaphases was observed after nitrofurazone treatment both with and without metabolic activation, but the gene mutation assay was negative. In vivo, despite the use of high doses of nitrofurazone (up to 400 mg/kg body weight) resulting in evidence of toxicity and a reduction in the mitotic index of bone-marrow cells, there was no evidence that nitrofurazone increased chromosomal damage. It is concluded that although the compound has the capacity to cause chromosomal damage in mammalian cells in vitro, it is detoxified by the metabolic system of the animal. These results, together with existing in vivo data, do not suggest that nitrofurazone is likely to give rise to any genotoxic hazard for man.

Animals↗
PubMed1984

Genetic damage in CHO cells exposed to enzymically generated active oxygen species.

The genetic toxicity of active oxygen species produced during the enzymic oxidation of xanthine has been investigated using Chinese hamster ovary (CHO) cells. Incubation of cells with xanthine plus xanthine oxidase resulted in extensive chromosome breakage and sister-chromatid exchange and gave a small increase in frequency of thioguanine-resistant cells (HGPRT test). Inclusion of superoxide dismutase or catalase in the xanthine/xanthine oxidase system inhibited chromosome breakage, whereas only catalase prevented SCE and mutant induction. It is concluded that hydrogen peroxide is responsible for most of the genetic effects observed in CHO cells exposed to xanthine/xanthine oxidase but that superoxide plays a key role in chromosome breakage.

Animals↗
PubMed1984

Protothecosis.

We have reported the 22nd case in the literature of protothecosis, a rare disease of man and animals due to infection with non-chlorophyll-producing algae of the genus Prototheca. The skin is most often affected, but generalized, disseminated involvement has been reported. Infection is usually severe and may be fatal. Amphotericin B in combination with tetracycline is the treatment of choice.

Female↗
PubMed1984

Antibodies to growth hormone-releasing factor inhibit somatic growth.

We have raised antibodies to rat growth hormone-releasing factor (GRF) which, when acutely administered to rats, cause a complete inhibition of pulsatile GH release. Using this passive immunization technique, we have evaluated the role of GRF in normal somatic growth. Twenty-two-day-old male Sprague-Dawley rats (61 +/- 2 g, mean +/- SEM) were treated for 16 days with either normal rabbit serum (n = 7) or rabbit antiserum raised against GRF (n = 7). During this period the BW of rats treated with normal rabbit serum increased 8.3 +/- 0.4 g/day while rats treated with GRF antiserum increased 4.3 +/- 0.2 g/day (P less than 0.01). These rats were then left untreated for an additional 22 days to determine whether animals treated with GRF antiserum would demonstrate a period of catch-up growth. Rats treated with normal rabbit serum continued to increase in BW at 8.1 +/- 0.4 g/day. Remarkably, rats treated with GRF antiserum continued to have a reduced growth rate, 5.4 +/- 0.6 g/day (P less than 0.01). This reduced growth rate was not due to long-term suppression of GH, since the patterns of pulsatile secretion and concentrations of plasma GH were not different between the two groups when measured three weeks after termination of the GRF antiserum treatment. These results demonstrate that GRF has a primary role in somatic growth and suggest that its presence during postnatal development is required to ensure subsequent normal somatic growth.

Animals↗