Genotoxicity testing of chloramphenicol in rodent and human cells

The results of this work, carried out to extend the limited information at present available on the genotoxic potential of chloramphenicol (CAP), indicate that in millimolar concentrations this antibacterial agent produced a minimal amount of DNA fragmentation in both V79 cells and metabolically competent rat hepatocytes. Moreover, a level of DNA-repair synthesis indicative of a weak but positive response was detected in primary cultures of liver cells obtained from 2 of 3 human donors, and a borderline degree of repair was present in those prepared from rats. The promutagenic character of CAP-induced DNA lesions was confirmed by a low but significant increase in the frequency of 6-thioguanine-resistant clones of V79 cells, which, however, was absent when the exposure was done in the presence of co-cultured rat hepatocytes. Finally, oral administration to rats of 1/2 LD50 CAP did not increase the incidence of either micronucleated polychromatic erythrocytes or micronucleated hepatocytes. Taken as a whole these findings suggest that CAP should be considered a compound intrinsically capable of producing a very weak genotoxic effect, but only at concentrations about 25 times higher than those occurring in patients treated with maximal therapeutic dosages.     

Biology ofPterolonche inspersa (Lep.: Pterolonchidae), a biological control agent forCentaurea diffusa andC. maculosa in the United States

The moth,Pterolonche inspersa (Staudinger) (Lepidoptera: Pterolonchidae), is widely distributed in southern Europe, north Africa, Turkey and the former Soviet Union. It occurs in both thick and scattered stands of knapweeds in disturbed sites, usually on sandy and/or stony soil. Larvae bore in the roots of diffuse and spotted knapweeds (Centaurea diffusa De Lamarck andC. maculosa De Lamarck). There is one generation per year in northern Greece, and larvae feed in the roots for about 11 months during the growing season (August–September, to the following July–August). In the laboratory garden, emergence took place between the second half of July and the end of August, with peak emergence during mid August. In the field, adults were observed from early to late July. Female moths oviposited on rosettes during the first ten days of July and continued through the end of July. Eggs were laid singly or in groups of five or six, firmly attached to the leaves of the host plant. In the laboratory, females mated within 24 hours of emergence and the preoviposition period lasted 2.6±0.8 days. The oviposition period lasted 7.4±2.2 days and the average number of eggs per female was 142.2±59.2. The incubation period was 12±4.7 days; the pupal stage lasted 14.7±2.4 days; and females lived 15.8±2.4 days, while males lived 10.7±1.4 days. First instar larvae failed to survive on economically important Compositae in the generaCynara L.,Helianthus L.,Zinnia L. andCalendula L. (Dunnet al., 1989).     

The role of ecosystem transpiration in creating alternate moisture regimes by influencing atmospheric moisture convergence

The terrestrial water cycle links the soil and atmosphere moisture reservoirs through four fluxes: precipitation, evaporation, runoff, and atmospheric moisture convergence (net import of water vapor to balance runoff). Each of these processes is essential for sustaining human and ecosystem well-being. Predicting how the water cycle responds to changes in vegetation cover remains a challenge. Recently, changes in plant transpiration across the Amazon basin were shown to be associated disproportionately with changes in rainfall, suggesting that even small declines in transpiration (e.g., from deforestation) would lead to much larger declines in rainfall. Here, constraining these findings by the law of mass conservation, we show that in a sufficiently wet atmosphere, forest transpiration can control atmospheric moisture convergence such that increased transpiration enhances atmospheric moisture import and results in water yield. Conversely, in a sufficiently dry atmosphere increased transpiration reduces atmospheric moisture convergence and water yield. This previously unrecognized dichotomy can explain the otherwise mixed observations of how water yield responds to re-greening, as we illustrate with examples from China's Loess Plateau. Our analysis indicates that any additional precipitation recycling due to additional vegetation increases precipitation but decreases local water yield and steady-state runoff. Therefore, in the drier regions/periods and early stages of ecological restoration, the role of vegetation can be confined to precipitation recycling, while once a wetter stage is achieved, additional vegetation enhances atmospheric moisture convergence and water yield. Recent analyses indicate that the latter regime dominates the global response of the terrestrial water cycle to re-greening. Evaluating the transition between regimes, and recognizing the potential of vegetation for enhancing moisture convergence, are crucial for characterizing the consequences of deforestation as well as for motivating and guiding ecological restoration.     

The evolution and ecology of multiple antipredator defences

Prey seldom rely on a single type of antipredator defence, often using multiple defences to avoid predation. In many cases, selection in different contexts may favour the evolution of multiple defences in a prey. However, a prey may use multiple defences to protect itself during a single predator encounter. Such “defence portfolios” that defend prey against a single instance of predation are distributed across and within successive stages of the predation sequence (encounter, detection, identification, approach (attack), subjugation and consumption). We contend that at present, our understanding of defence portfolio evolution is incomplete, and seen from the fragmentary perspective of specific sensory systems (e.g., visual) or specific types of defences (especially aposematism). In this review, we aim to build a comprehensive framework for conceptualizing the evolution of multiple prey defences, beginning with hypotheses for the evolution of multiple defences in general, and defence portfolios in particular. We then examine idealized models of resource trade-offs and functional interactions between traits, along with evidence supporting them. We find that defence portfolios are constrained by resource allocation to other aspects of life history, as well as functional incompatibilities between different defences. We also find that selection is likely to favour combinations of defences that have synergistic effects on predator behaviour and prey survival. Next, we examine specific aspects of prey ecology, genetics and development, and predator cognition that modify the predictions of current hypotheses or introduce competing hypotheses. We outline schema for gathering data on the distribution of prey defences across species and geography, determining how multiple defences are produced, and testing the proximate mechanisms by which multiple prey defences impact predator behaviour. Adopting these approaches will strengthen our understanding of multiple defensive strategies.     

A simple test for predisposition to LDL oxidation based on the fluorescence development during copper-catalyzed oxidative modification

When human low density lipoprotein (LDL) obtained from 10 volunteers was incubated in air at 37 degrees C in the presence of various concentrations of copper, an increase in fluorescence was observed with emission maximum at 430 nm when excitation was performed at 360 nm. The fluorescence increase was inhibited by ethylenediamine tetraacetic acid and by 4-methyl-2,6-di-tert-butylphenol. The fluorescence was found to be tightly bound to the protein moiety. Furthermore, Cu2+ modification of LDL was associated with a decrease in the reactive amino groups of apolipoprotein B and in the uptake of the lipoprotein by rabbit fibroblasts. Under our conditions, the fluorescence increase showed two consecutive periods; an inhibition period during which the fluorescence increased only weakly, and a propagation period with a rapid increase in fluorescence that was linear for at least 5 h. Both periods were influenced by copper concentration. The study also shows that the extent of fluorescence generated upon LDL oxidation varied greatly in the volunteers. Thus, while the results demonstrate that the fluorescence increase may likely monitor the extent of the apoB derivatization, the calculation of the fluorescence development rate of the propagation period together with the duration of the inhibition period may constitute a quantitative measurement of the susceptibility of apoB to be derivatized.     

Conformational properties of the N-terminal residues of S-peptide. I. The ribonuclease S′ system

The contribution of the 1–6 N-terminal sequence to the conformational properties of the S-peptide (the 1–20 sequence of ribonuclease A) was assessed by determining in the ribonuclease S′ system the helical content and the binding capability of synthetic [Orn¹⁰]-S-peptide analogs, in which lysine¹, glutamic² and threonine³ were progressively deleted, alanine⁴ and alanine⁵were alternatively replaced by serine, and alanine⁶ was substituted by serine or proline. Both the deletion of the three N-terminal residues and the alanine⁶/proline replacement produces the loss of the helical structure up to lysine⁷. No or minor effects are found in all other cases. From the comparison of the binding data, the energy for the conformational stabilization of the N-terminal region was calculated to amount to 1.4 kcal/mol. The results are discussed in comparison with the known x-ray data of the enzyme, with some predictive rules of secondary structure which were applied to this region and with the known phylogenetic variance of the residues in this region.     

Biosynthesis of the sesquiterpenoid ageratriol

Ageratriol is biosynthesized from agerol through a diepoxide derivative. Mevalonic acid incorporation revealed that the formation of the isopropenylic double bond is not stereospecific.     

Reflexions sur nos cultures d'antheres de plantes cultivées

Abstract

Considerations about our anther cultures of cultivated plants. – One of the main activities performed at the Casaccia Nuclear Centre, in the framework of a contract between CNEN and the European Communities, centers on the induction of haploid plants by anther culture and the subsequent chromosome doubling in order to obtain completely homozygous diploid plants. In tobacco, it is now possible to obtain haploid plants from any cultivar; we perform in vitro culture of internodes from which homozygous diploid plants are regenerated, taking advantage of natural phenomenon of endopolyploidy. In order to try to generalize this method of producing haploid plants in other plant species, we are studying the mechanism involved in haploid embryogenesis which occurs in vitro in the microspores. Datura, Nicotiana and Atropa are among the genera in which a direct embryogenesis from the microspore is observed; it is interesting to note that all three genera belong to the family Solanaceae and are very rich in alkaloids. In almost all the other cases of in vitro induction of haploids, microspores produce calli from which plantlets can be differentiated, but this way of plant regeneration is less interesting because only few plantlets are obtained and it is not sure that each haploid comes from a single microspore. We examined the factors which could influence the transformation of microspores into embryoids in tobacco, namely: the developmental stage of microspore, the degeneration of tapaetal cells, the genotype of microspore, the composition of cultural media, the physiological conditions of the plant from which the anthers were taken. From a practical point of view, it would be desirable to have informations on methods giving a maximum number of haploid plants from one embryogenic anther and the greatest number of embryogenic anthers from the cultured anthers. Our recent experiments on anther culture in liquid shaken medium have yielded good results (about 7,000 embryoids from 25 embryogenic anthers). Further, we are conducting several experiments in order to synchronize the development of the microspores in the anthers; to this end, we analyse the effect of cold treatment, ionizing radiation and gravity force. Experiments are being performed with other cultivated species, beside tobacco, in order to solve some problems of plant breeding more easily and quickly through haploidy. With the aim of introducing, in cultivated tomato, some desirable characters from the wild species, Lycopersicum peruvianum, (self-incompatibility, disease resistance, simultaneous flowering), we have obtained the interspecific hybrid through in vitro culture of young embryos. Haploid production from this hybrid could allow to quickly obtain various genetic recombinations from these two species. For this purpose we are carrying out anther cultures as well as single microspore cultures. In rice, strawberry and L. peruvianum, several diploid and tetraploid plantlets were obtained from our anther cultures. Work is in progress to ascertain the mode of their origin.     

MicroRNA-486-3p Regulates γ-Globin Expression in Human Erythroid Cells by Directly Modulating BCL11A

MicroRNAs (miRNAs) play key roles in modulating a variety of cellular processes through repression of mRNAs target. The functional relevance of microRNAs has been proven in normal and malignant hematopoiesis. While analyzing miRNAs expression profile in unilineage serum-free liquid suspension unilineage cultures of peripheral blood CD34⁺ hematopoietic progenitor cells (HPCs) through the erythroid, megakaryocytic, granulocytic and monocytic pathways, we identified miR-486-3p as mainly expressed within the erythroid lineage. We showed that miR-486-3p regulates BCL11A expression by binding to the extra-long isoform of BCL11A 3′UTR. Overexpression of miR-486-3p in erythroid cells resulted in reduced BCL11A protein levels, associated to increased expression of γ-globin gene, whereas inhibition of physiological miR-486-3p levels increased BCL11A and, consequently, reduced γ-globin expression. Thus, miR-486-3p regulating BCL11A expression might contributes to fetal hemoglobin (HbF) modulation and arise the question as to what extent this miRNA might contribute to different HbF levels observed among β-thalassemia patients. Erythroid cells, differentiated from PB CD34⁺ cells of a small cohort of patients affected by major or intermedia β-thalassemia, showed miR-486-3p levels significantly higher than those observed in normal counterpart. Importantly, in these patients, miR-486-3p expression correlates with increased HbF synthesis. Thus, our data indicate that miR-486-3p might contribute to different HbF levels observed among thalassemic patients and, possibly, to the clinical severity of the disease.