Study of the causes of direct-acting mutagenicity in coffee and tea using the Ara test in Salmonella typhimurium

The mutagenic activities of 6 of the chemicals identified in coffee solutions were assayed with the Salmonella Ara test, under experimental conditions optimized for coffee mutagenicity. Caffeine was the only non-mutagenic compound. Among the other 5 chemicals, hydrogen peroxide was the strongest mutagen and chlorogenic acid the weakest; methylglyoxal, glyoxal and caffeic acid exhibited intermediate mutagenicities. The minimal mutagenic doses of these components correlated negatively with their relative concentrations in coffee. It was concluded that chlorogenic acid, caffeic acid, glyoxal and methylglyoxal cannot contribute alone to the mutagenicity of coffee in the Ara test, since their minimal mutagenic concentrations were much higher than their respective levels in the coffee samples assayed. By contrast, 40-60% of the mutagenic activity in coffee and also in tea could be attributed to their H2O2 contents. Catalase abolished more than 95% of the mutagenic activity of coffee, as detected by the Ara test. A similar sensitivity to catalase has been reported by other authors in relation to the coffee mutagenicity identified by the Salmonella His test. Nevertheless, the results presented in this paper suggest that the Ara forward and the His reverse mutation tests are sensitive to the mutagenicity of different constituents in coffee solutions. We propose that the His test, sensitive at high coffee doses, mainly recognizes the mutagenicity of methylglyoxal, whilst the Ara test, sensitive at low coffee doses, mainly detects the mutagenic activity of hydrogen peroxide. The data reported also suggest that the direct-acting mutagenicity(ies) detected by the Ara test in tea solutions is (are) based on similar, if not identical, mechanisms.     

Effects of membrane depolarization and divalent cations on anaphylactic histamine secretion

The effects of membrane depolarization and divalent cations on histamine release have been studied in sensitized mast cells. Membrane potential of these cells has been measured with intracellular microelectrodes. Our results show that mast cells have a large resting potential (-61 +/- 12 mV) however they do not generate active membrane electrical responses when are depolarized by passing current through the recording microelectrode. High external K+ does not increase histamine release. Histamine secretion is supported by alkali-earth divalent cations (Ca2+ greater than Sr2+ greater than Ba2+) but strongly inhibited by transition metals. Ca2+ concentrations above 1 mM inhibit histamine release, however, this effect is not mimicked by Sr2+ and Ba2+.     

Two modes of cell migration in the ventral horn of the spinal cord in the chick embryo. A Golgi study

The migration process of the ventral horn in chick embryo spinal cord cells has been studied between 2.5 and 5 days of incubation (HH-17, HH-26), using the Golgi technique. Two different migratory modes are observed. Type I--Migration by nucleus translocation. Most of the ventral horn motor neurons migrate by nucleus translocation within the peripheral cylinder of the cytoplasm (migration by nucleus translocation). Type II--Free migration cells. Other cells migrate disconnected from both limiting surfaces (ventricular and pial). On the basis of shape and migratory behaviour they have been identified as smooth cells and multipodial cells.     

Insulin and insulin-like growth factor I in follicular fluid after induction of ovulation in women undergoing in vitro fertilization.

This study was undertaken to evaluate the relationship between concentrations of insulin and insulin-like growth factor I (IGF-I) in follicular fluid and fertilization and cleavage of human oocytes fertilized in vitro. The concentration of oestradiol, progesterone, luteinizing hormone, follicle-stimulating hormone, testosterone, insulin and IGF-I was determined in 36 follicular fluids, free of visible blood contamination and containing mature oocyte-corona-cumulus complexes, obtained from 12 women undergoing in vitro fertilization. Follicular development was induced by clomiphene citrate and human menopausal gonadotrophin, and follicular aspiration was performed 35 h after an ovulatory dose of human chorionic gonadotrophin. Concentrations of IGF-I were significantly higher in follicular fluids associated with mature oocytes that fertilized and cleaved, than in follicular fluid associated with mature oocytes that did not fertilize (P < 0.001). There was no difference in the concentration of insulin between follicular fluids from which fertilized oocytes were obtained and those with oocytes that remained unfertilized. No significant correlations were found between rates of embryo cleavage, concentrations of insulin and IGF-I. Multiple linear regression analysis demonstrated that the concentrations of IGF-I in follicular fluid were predicted statistically by a negative regression coefficient for the concentration of testosterone, and by a positive regression coefficient for the concentration of progesterone in follicular fluid. No candidate variable was included in the model to predict concentrations of insulin. These data suggest an important role for IGF-I in the mature follicle.     

On the genetic parameter determining the efficiency of purging: an estimate for Drosophila egg‐to‐pupae viability

The consequences of inbreeding on fitness can be crucial in evolutionary and conservation grounds and depend upon the efficiency of purging against deleterious recessive alleles. Recently, analytical expressions have been derived to predict the evolution of mean fitness, taking into account both inbreeding and purging, which depend on an ‘effective purging coefficient (d_e)’. Here, we explore the validity of that predictive approach and assay the strength of purging by estimating d_e for egg‐to‐pupae viability (EPV) after a drastic reduction in population size in a recently captured base population of Drosophila melanogaster. For this purpose, we first obtained estimates of the inbreeding depression rate (δ) for EPV in the base population, and we found that about 40% was due to segregating recessive lethals. Then, two sets of lines were founded from this base population and were maintained with different effective size throughout the rest of the experiment (N = 6; N = 12), their mean EPV being assayed at different generations. Due to purging, the reductions in mean EPV experienced by these lines were considerably smaller than the corresponding neutral predictions. For the 60% of δ attributable to nonlethal deleterious alleles, our results suggest an effective purging coefficient d_e > 0.02. Similarly, we obtain that d_e > 0.09 is required to roughly account for purging against the pooled inbreeding depression from lethal and nonlethal deleterious alleles. This implies that purging should be efficient for population sizes of the order of a few tens and larger, but might be inefficient against nonlethal deleterious alleles in smaller populations.