Search PubMed⌕ Search

Biomedical subjects

M H Green

Publications and source records attributed to M H Green.

At least 73 records · Page 4Linked to original sources
PubMed1995

Absence of evidence for mutagenicity of alcoholic beverages: an analysis of hprt mutant frequencies in 153 normal humans.

A substantial database on hprt mutant frequency in circulating T-cells derived from 153 normal humans was analysed to determine if any effect of alcohol consumption could be detected. Alcohol intake (as reported in a questionnaire completed at the time of the blood sample) ranged from 0 to 35+ units per week. Donors were classified into four groups, including total abstainers (n = 18); those who consumed less than the Royal College of Physicians guideline (men, 21 units; women, 14 units) (n = 113); those who consumed more than the guideline value (n = 12); and designated alcohol-dependent subjects (n = 10). No significant difference in mutant frequency between the four groups was found, nor was an overall correlation between alcohol consumption and mutant frequency seen.

Acetaldehyde↗
PubMed1995

Mutant frequencies in workers at the Sellafield installation.

The frequency of hypoxanthine-guanine phosphoribosyltransferase (hprt) mutations has been determined in the peripheral T-lymphocytes of 18 workers at the Sellafield nuclear reprocessing installation with cumulative recorded radiation doses of about 500 mSv or more in comparison with a matched control group of 18 workers with doses less than 50 mSv. The mean dose of the exposed group was 663 mSv (range 449.3-880.8), and of the unexposed group 10.9 mSv (range 0-46.5). During the most recent 6 y the mean doses were 40.1 mSv (range 1.9-93.9) and 2.3 mSv (range 0-8.7), respectively. The logarithmic mean mutant frequency of the exposed group (9.3 x 10(-6)) was lower than that of the unexposed group (12.4 x 10(-6)). The apparent inverse association of mutant frequency and exposure varied in statistical significance tests from borderline to p < 0.01 depending on how the analysis was performed and whether recent or total exposure was considered.

Humans↗
PubMed1995

Effects of N-(4-hydroxyphenyl)retinamide on vitamin A metabolism in rats.

Chronic administration of the anticancer drug N-(4-hydroxyphenyl)-retinamide (4-HPR) causes reductions in the plasma levels of vitamin A and its transport protein, retinol-binding protein. Here, we used model-based compartmental analysis to study effects of 4-HPR on the whole-body kinetics of vitamin A metabolism in rats. Rats (n = 8) were fed a purified diet containing vitamin A (approximately 49 nmol retinol/day) plus 0 or approximately 50 mumole 4-HPR/(kg body wt.day). Plasma retinol kinetics were monitored for 35 days after intravenous administration of [3H]retinol-labeled plasma. 4-HPR caused an 80% reduction in plasma retinol; after 40 days of treatment with 4-HPR, liver vitamin A levels were 2.33 times higher than those of control rats. A three compartment model, in which plasma retinol exchanges with two extravascular compartments, was required to fit data for both groups. Vitamin A input was via the central plasma compartment, while irreversible loss was via the larger extravascular compartment. The time retinol spent in plasma before reversible or irreversible exit was normal (1.7 hr) in 4-HPR-treated rats, but the rate of plasma retinol turnover was reduced, and the recycling of retinol to plasma was delayed and reduced. Vitamin A utilization was significantly lower in 4-HPR-treated rats (20 nmol retinol/day vs 42 nmol/day in controls). We conclude that 4-HPR partially blocks access and thus binding of retinol to retinol-binding protein and may therefore lead to vitamin A accumulation in certain cells.

Animals↗
PubMed1995

Dietary cholesterol and fat saturation effects on plasma esterified and unesterified cholesterol in selected lines of Japanese quail females.

Three lines of Japanese quail females, randombred controls (CL), high response (HL), and low response (LL) lines, selected for plasma total cholesterol for 18 generations, were fed all-plant-source, nonatherogenic diets to which 0 or .5% cholesterol were added from 6 to 18 wk of age. In all three lines, plasma cholesterol increased when cholesterol was fed; however, responses were greater in the HL than in the LL line, with CL intermediate. In a second experiment, females of the three lines were fed, from 6 to 14 wk of age, four isocaloric, isonitrogenous plant-source diets to which were added: 1) 10% glucose monohydrate (cerelose); 2) 10% cerelose + .1% cholesterol; 3) 4% corn oil; or 4) 4% coconut oil. Baseline data obtained before feeding experimental diets indicated that the HL had significantly higher plasma total, esterified (EC) and unesterified (UEC) cholesterol than LL and that nonovulating females had higher concentrations of esterified cholesterol than ovulating females. Diets used did not affect cholesterol fractions in the ovulating females, although there were significant differences among lines. Dietary cholesterol significantly increased the ratio of EC to UEC. Sclerotic lesion scores were higher in the HL than the LL birds and in birds fed the coconut oil diet.

Analysis of Variance↗
PubMed1994

DNA strand breakage, cytotoxicity and mutagenicity of hydrogen peroxide treatment at 4 degrees C and 37 degrees C in L5178Y sublines.

Cells from the L5178Y murine lymphoma subline LY-R are twofold more resistant to killing by ionizing radiation than the subline LY-S. In contrast, LY-R cells are more sensitive to killing by hydrogen peroxide. Cells of the two sublines in logarithmic growth phase were treated with hydrogen peroxide in phosphate-buffered saline for 1 h at 4 degrees C or 37 degrees C. From the comparison of D(o) values it followed that at 37 degrees C LY-R were 3.6 times more sensitive to the killing effect of H2O2 than LY-S cells; at 4 degrees C they were 11 times more sensitive. Treatment with hydrogen peroxide at 4 degrees C gave a considerable sparing effect, which was substantially greater for the LY-S subline; for LY-S cells D(o) was 5.7 times lower at 37 degrees C than at 4 degrees C, for LY-R cells only 1.9 times. The mutation frequency (HGPRT) in LY-R cells was increased in proportion to H2O2 concentration and was the same at both treatment temperatures. In contrast, mutation frequencies initially increased, then decreased with increasing H2O2 concentration in LY-S cells treated at 4 or 37 degrees C. The concentration at which the decline was initiated was higher at 4 than at 37 degrees C. DNA damage after H2O2 treatment (both temperatures, 5 min) was estimated from the 'comet' assay (single-cell gel electrophoresis). The initial damage, but not the residual damage, differed significantly in LY sublines. A period of slower repair (between 3 and 10 min) was found in LY-R cells.

Animals↗
PubMed1994

Effects of dietary rhIGF-I in neonatal calves on the appearance of glucose, insulin, D-xylose, globulins and gamma-glutamyl transferase in blood.

Cow colostrum is rich in insulin-like growth factors IGF-I and II, thus the dietary effects of recombinant human (rh) rhIGF-I on the newborn were of interest. The objective of this study was to examine the effect of dietary IGF-I upon selected blood components and gut absorptive development. Calves were blocked by birth weight and fed two times per d for a total of four times with the initial restricted diet. The initial feeding was 1.5 l and the remaining three feedings were at 2 l with one of three experimental diets; 1) milk replacer plus isolated colostrum derived globulins (MR-), 2) same as 1 above plus 750 ng/ml rhIGF-I (MR+), 3) pooled cow colostrum (COL). Thereafter, all animals received only milk replacer at 5% of body weight (BW)/feeding two times per d with only treatment 2 having continued addition of 750 ng/ml rhIGF-I until experimental completion at 6 to 7 d after birth. At feeding three, animals were fed D-xylose (0.5 g/kg BW) and 5,000 U of bovine kidney membrane gamma-glutamyl transferase as indicators of gut absorptive capacity. Colostrum-fed animals received 5,000 U of natural occurring gamma-glutamyl transferase activity in the 1.5 l first feeding. Blood samples taken over time were collected and saved as frozen plasma. All diets were analyzed for nutrient composition and endogenous levels of test hormones. Colostrum fed calves had greater globulin concentration (P < 0.01) than MR- or MR+ fed calves. Recombinant hIGF-I feeding had no effect (MR- vs. MR+) upon total protein, albumin or globulin blood levels. Absorption of colostrum gamma-glutamyl transferase at first feeding resulted in a peak total blood U of 4.5% of that fed. Although enzyme absorption was greatly reduced by the third feeding (0.5% of total fed), MR+ fed calves exhibited no significant difference in enzyme absorption when compared with the controls (MR- vs. MR+). However, pharmacokinetic analysis of D-xylose absorption at the third feeding showed diet effect upon absorption of D-xylose. Dietary rhIGF-I may change development or activity of sugar transporters and also may alter absorption of macromolecules (closure) in neonatal calves.

Animal Feed↗
PubMed1994

Effect of diet and vitamin C on DNA strand breakage in freshly-isolated human white blood cells.

We have measured DNA strand breaks induced by ionising radiation in nucleated cells from freshly isolated whole blood from normal human subjects. Samples were taken after subjects had fasted overnight and again 1 h after they had eaten breakfast in combination with approximately 35 mg/kg vitamin C. Damage was measured by single cell gel electrophoresis (the 'comet' assay), in which DNA single strand breaks generate a comet tail streaming from the nucleus. In repeat experiments on 6 subjects a reduction in DNA damage, as indicated by a highly significant decrease in overall comet length, was observed following vitamin C ingestion, both in the unirradiated control blood samples and in the dose response to ionising radiation damage. In addition, consistent differences in dose response between individual subjects were found. The peak effect was 4 h after intake of food and vitamin C. An effect was also seen with vitamin C alone and after breakfast without additional vitamin C. Protection against strand breakage was also seen in Ficoll-separated mononuclear cells but evidence was not obtained for protection of separated, mitogen stimulated T-lymphocytes either against ionising radiation cell killing in a clonal assay, or against clastogenicity assessed by micronucleus formation following one cell division. Exposure of separated lymphocytes in vitro to vitamin C, at doses greater than 200 microM, did not offer protection but induced strand breakage. Our results raise the possibility that variation in normal diet may not only affect susceptibility to endogenous oxidative damage, but may affect some responses of the individual to radiation.

Artifacts↗
PubMed1994

Effect of deoxyribonucleosides on the hypersensitivity of human peripheral blood lymphocytes to UV-B and UV-C irradiation.

We have previously shown that non-cycling (unstimulated) human lymphocytes from normal donors show extreme hypersensitivity to UV-B irradiation, and are killed by an excisable lesion which is not a pyrimidine dimer or 6-4 photoproduct. In this paper we show that addition of the 4 deoxyribonucleosides to the medium, each at 10(-5) M, substantially increased the survival of non-cycling normal human T-lymphocytes following UV-B irradiation and substantially reduced the frequency of excision-related strand breaks in human mononuclear cells. Addition of ribonucleosides to the medium did not enhance excision-break rejoining. The survival of fibroblasts, of cycling T-lymphocytes and of unstimulated xeroderma pigmentosum T-lymphocytes was not enhanced by deoxyribonucleosides. This suggests that the hypersensitivity is due to reduced rejoining of excision breaks as a consequence of low intracellular deoxyribonucleotide pools and that it can be redressed by supplementation of the medium with deoxyribonucleosides or upregulation of ribonucleotide reductase following mitogen stimulation. We suggest that UV-B forms an additional DNA lesion which is not a pyrimidine dimer or 6-4 photoproduct, which is relatively common, and at which incision is particularly efficient. In fibroblasts, repair of this lesion is completed with high efficiency, whereas in normal unstimulated T-lymphocytes, rapid incision exacerbates the effects of the reduced rate of strand rejoining and leads to cell death.

Cells, Cultured↗
PubMed1994

Fever and the control of gram-negative bacteria.

Although it seems obvious that fever has some important general adaptive value, it is still not clear by what means this function is manifested. One postulate is that febrile conditions result in the sequestration of soluble iron, effectively starving some pathogens of that essential nutrient. On the basis of our recent experiments, we propose a new mechanism for how fever serves to restrict a wide range of Gram-negative bacteria. The elevated temperature prevents the bacteria from synthesizing their protective LPS, thereby enabling serum complement to perforate and kill the invading pathogens even prior to the production of host antibodies.

Body Temperature↗
PubMed1994

Vitamin A intake and status influence retinol balance, utilization and dynamics in rats.

To study effects of vitamin A status on retinol dynamics, male rats were fed purified diets varying in vitamin A concentration. Group 1 rats had marginal liver vitamin A levels (approximately 500 nmol) and were in a slight positive vitamin A balance; Group 2 had similar liver levels but were in a slight negative balance; Group 3 had lower liver levels (approximately 370 nmol) and were in a slight negative balance; Group 4 had depleted liver reserves (<10 nmol) and were in vitamin A balance. [3H]Retinol-labeled plasma was injected intravenously, and serial plasma samples were collected for 41 d while rats (six per group) consumed approximately 50 nmol retinol/d (Group 1) or -25 nmol/d (Groups 2-4). Plasma retinol was normal in Groups 1-3 (1.9-2.0 micromol/L) and lower in Group 4 (0.96 micromol/L). Plasma tracer data were fit to a three-compartment model. The central plasma retinol compartment (transit time, 1.5-1.7 h) exchanged with a fast turning-over extravascular vitamin A pool (transit time, 3-4.5 h; -40 nmol) and with a larger, slow turning-over extravascular pool (transit time, 5.5-10 d) that was the site of irreversible utilization of vitamin A. Irreversible utilization was 36 nmol/d (Group 1), 29 nmol/d (Groups 2 and 3) and 20 nmol/d (Group 4). The data indicate that in rats with low or marginal vitamin A status, vitamin A intake, vitamin A reserves and plasma retinol concentration all influence vitamin A utilization and other aspects of retinol dynamics.

Animals↗
PubMed1994

Prediction of liver vitamin A in rats by an oral isotope dilution technique.

Male Sprague-Dawley rats (n = 41) that had liver vitamin A levels ranging from 5 nmol to 22 mumol (0.48 to 1629 nmol/g) were intubated with [3H]retinol in oil (167 kBq/rat). Plasma samples collected at 3, 4, 4.4, 5, 5.4 and 6 d were analyzed for radioactivity, and liver vitamin A mass was determined at 8 d. Nonlinear regression analysis was used to develop a biexponential equation describing the relationship at each sampling time between fraction of the dose remaining in plasma (FDp) and liver vitamin A. The best equation, developed with 3-d data, was liver vitamin A (nmol) = 58,577 x exp(-2715 x FDp) + 1810 x exp(-127 x FDp); Spearman's rank correlation coefficient = 0.982. This equation showed good predictive ability as evidenced by the ratio of the calculated to the observed liver vitamin A (1.23 +/- 0.65) and by its ability to distinguish animals with deficient, marginal, adequate or high vitamin A status. We conclude that this sensitive, noninvasive procedure can be used to predict rat liver vitamin A over a wide range.

Animals↗
PubMed1994

An in vitro assay of anterior cruciate ligament (ACL) and medial collateral ligament (MCL) cell migration.

Explants from rabbit anterior cruciate ligaments (ACL) and medial collateral ligaments (MCL) were utilized to compare the relative rates that fibroblasts migrate onto glass and plastic culture surfaces in vitro. During the first two weeks in culture, a monolayer of cells appeared on the periphery of all the ACL and MCL explants. From 45 to 134 hrs in culture, the mean total MCL cell count per explant was 6-12 times greater than that for the ACL on the plastic culture dishes, and this difference was even greater for the cells attached to the glass cover slides over the explants. These differences were significant at the p < .005 level. The rates of cell proliferation were quite similar for primary cultures of ACL and MCL grown in the same medium as that used for the migration assay. The large difference in cell number at early times of culture is thus due to the more rapid MCL cell migration out of the explants, and not to a difference in the rate of cell proliferation. These data support the hypothesis that differences in cell migration rate play a role in the greater healing capacity of the MCL as compared with the ACL. The assay described in this work may then be useful in assessing factors that promote wound healing.

Animals↗
PubMed1993

Endogenous nitric oxide induced by interleukin-1 beta in rat islets of Langerhans and HIT-T15 cells causes significant DNA damage as measured by the 'comet' assay.

We have used the comet assay (single cell gel electrophoresis) to measure nitric oxide-induced DNA damage in rat islets of Langerhans and insulin-containing HIT-T15 cells. Damage was induced following treatment with the nitric oxide donor SIN-1, which also releases superoxide, but was not reduced by exogenous superoxide dismutase, suggesting that nitric oxide itself, rather than superoxide or peroxynitrite may be the active species. The DNA damaging effect of nitric oxide was easily detectable at the earliest time point tested (15 min). Damage also resulted following induction of nitric oxide synthase by the cytokine interleukin-1 beta in both islets and HIT-T15 cells and was prevented by replacing the substrate, arginine, with nitromonomethyl arginine. Thus intracellular levels of nitric oxide generated by interleukin-1 beta-induced nitric oxide synthase were sufficient to cause DNA damage in islet cells and HIT-T15 cells.

Animals↗
PubMed1993

Hypersensitivity of human lymphocytes to UV-B and solar irradiation.

T-lymphocytes from three normal human donors, irradiated with broad-spectrum UV-B (peak emission, 312 nm), are 20-fold more sensitive than fibroblasts from four normal donors in a clonogenic assay. We have compared the formation of thymine cyclobutane dimers and pyrimidine-(6-4)-pyrimidone photoproducts following irradiation by UV-C (254 nm) and UV-B and studied killing at doses giving equal dimer formation. UV-B killing of fibroblasts appears to be associated with dipyrimidine photoproduct formation, whereas UV-B killing of lymphocytes is mediated by nondimer damage. Strand breakage following UV-B irradiation measured using the "Comet" assay (single cell gel electrophoresis) reflects this nondimer damage and has kinetics consistent with excisable damage. Lymphocytes from three excision-deficient xeroderma pigmentosum donors show reduced strand breakage and increased killing following UV-B irradiation, compared with lymphocytes from normal donors. We therefore suggest that UV-B kills human lymphocytes by excisable nondimer damage and that xeroderma pigmentosum lymphocytes are defective in its repair. The putative nondimer damage does not appear to be associated with radical attack, and the strand breakage is not a manifestation of apoptosis. A 1-min exposure of human lymphocytes in vitro to natural sunlight is sufficient to produce damage measurable by the Comet assay.

Apoptosis↗
PubMed1993

The single cell gel electrophoresis assay (comet assay): a European review.

The single cell gel electrophoresis (SCGE) assay is a rapid, simple, visual and sensitive technique for measuring DNA breakage in individual mammalian cells. Here we review the development of the SCGE assay (with particular reference to the alkaline version), existing protocols for the detection and analysis of comets, the relevant underlying principles determining the behaviour of DNA, and the potential applications of the technique.

Animals↗
PubMed1993

Liver vitamin A levels in rats are predicted by a modified isotope dilution technique.

We tested the hypothesis that the fraction of an injected dose (FDp) of [3H]retinol remaining in plasma could be used to predict liver vitamin A mass. Rats (n = 36) with liver vitamin A ranging from 1.4 to 23,000 nmol received an intravenous dose of [3H]retinol-labeled plasma. Plasma samples obtained at 4, 4.4, 5, 5.4, 6, 7 and 8 d were analyzed for radioactivity; liver vitamin A levels were determined at 8 d. Using a regression equation developed previously [liver vitamin A (nmol) = 7493.exp(-148.FDp)], there was a log linear relationship between FDp and liver vitamin A mass from 1.4 to 5200 nmol retinol; the equation did not predict levels > or = 7500 nmol. By expanding the regression equation [liver vitamin A (nmol) = 88,928.exp(-1347.FDp) + 5606.exp(-120.FDp)] and using the FDp at 4.4 d, liver vitamin A levels ranging from < 4 to 23,000 nmol were well predicted. Satisfactory equations were also developed for data obtained at 4, 5 and 5.4 d. We conclude that this modified isotope dilution technique is a sensitive and reliable method for assessing vitamin A status in rats over a wide range of vitamin A nutriture. It is likely that this method could be modified for use in humans.

Animals↗