Sporophytic response to pollen selection for Alachlor tolerance in maize

In order to assess the efficiency of male gametophytic selection (MGS) for crop improvement, pollen selection for tolerance to herbicide was applied in maize. The experiment was designed to test the parallel reactivity to Alachlor of pollen and plants grown in controlled conditions or in the field, the response to pollen selection in the sporophytic progeny, the response to a second cycle of MGS, and the transmission of the selected trait to the following generations. The results demonstrated that pollen assay can be used to predict Alachlor tolerance under field conditions and to monitor the response to selection. A positive response to selection applied to pollen in the sporophytic progeny was obtained in diverse genetic backgrounds, indicating that the technique can be generally included in standard breeding programs; the analysis of the data produced in a second selection cycle indicated that the selected trait is maintained in the next generation.     

Effects of estrogen-depletion on rat casein gene expression

Mammary tissue from rats that had been ovariectomized and adrenalectomized 4 weeks previously was compared to that from intact rats in terms of epithelial content and hormone-responsiveness in vitro. The endocrinectomy resulted in about a 30% enlargement of the gland, but led to a loss of only about 12% of the epithelium. This estrogen-depleted epithelium was able to acquire full responsiveness in vitro to insulin in terms of the accumulation of alpha-aminoisobutyric acid, and induction of glucose-6-phosphate and gluconate-6-phosphate dehydrogenases. It was also fully responsive to cortisol in relation to the induction of NADH-cytochrome C reductase, and to prolactin in terms of total RNA synthesis. However, estrogen-depletion led to an 82% loss in the ability of a unit amount of the epithelium to synthesize casein in response to these 3 hormones, and to a similar loss in relation to the accumulation of 25K casein mRNA. Estrogen administration in vivo could prevent and reverse the casein lesion. The disparity between constitutive and casein hormone-responsiveness in the absence of estrogen is discussed in relation to cell commitment.     

Lead effect on the oxidation resistance of erythrocyte membrane in rat triton-induced hyperlipidemia

The anemia observed in severe chronic lead poisoning is in part attributable to alterations in the erythrocyte physicochemical properties. Since they are partly related to the membrane lipid composition, the aim of the present study was to determine the effects of a triton-induced hyperlipidemia on the resistance to oxidation of erythrocyte membranes in lead-treated Wistar rats. Our results showed that triton administration to lead-treated rats induced an increase in erythrocyte choline phospholipid levels together with a significant decrease in the erythrocyte membrane lipid resistance to oxidation. These results led us to suggest that anemia in lead poisoning is linked to interactions between lead present in the membrane and plasma phospholipids. Their increase in rat hyperlipidemia induced by triton resulted in a decrease in the membrane resistance to oxidation and finally in an erythrocyte fragility leading to their destruction.     

Immunosenescence: potential causes and strategies for reversal

Age-related deterioration in immune function has been recognized in many species. In humans the clinical manifestation of such immune dysfunction is age-related increases in the susceptibility to certain infections and in the incidence of some autoimmune disease and certain cancers. Laboratory investigations reveal age-related changes in the peripheral T cell pool, in the predominant phenotype, cytokine production profiles, signalling function and in replicative ability following stimulus with antigen, mitogens or anti-CD3 antibody. These changes in the properties of peripheral T cells are thought to be causally linked to an age-associated involution in the thymus. Our analysis reveals that thymic involution is due to a change in the thymic microenvironment linked to a reduction in the level of available interleukin 7. Treatment with interleukin 7 leads to a reversal of thymic atrophy with increased thymopoiesis. This provides the potential to reverse the immune dysfunction seen in the peripheral T cell pool by replacing old cells with new output generated in the thymus. Problems to overcome in order for such an experimental therapy to be successful require careful analysis in order to provide an optimal strategy to ensure that new T cell emigrants from the thymus have a broad range of specificities and are able to enter the peripheral T cell pool.     

Localization of repetitive DNA sequences on in vitro Xenopus laevis chromosomes by primed in situ labeling (PRINS)

Xenopus laevis is an important reference model organism used in many vertebrate studies. Gene mapping in X. laevis, in comparison to other reference organisms, is in its early stages. Few studies have been conducted to localize DNA sequences on X. laevis chromosomes. Primed in situ labeling (PRINS) is a recently developed innovative tool that has been used to locate specific DNA sequences in various organisms. PRINS has been reported to have increased sensitivity compared to other in situ hybridization techniques. In the present study, PRINS was first used to label the location of telomeres at the ends of in vitro X. laevis chromosomes. The terminal location was as expected from in vivo reports, however, the overall amount seemed to decrease in the in vitro chromosomes. Once the PRINS technique was optimized, this technique was used to determine the chromosomal location of the satellite 1 repetitive sequence, which is an important sequence in X. laevis development. The sequence was observed on the interstitial regions of the majority of the chromosomes similar to the in vivo locations reported. In contrast to the telomeric sequence, the amount of sequence appeared to increase in the satellite 1 sequence. PRINS was found to be useful in the localization of repetitive DNA sequences in the X. laevis genome.     

HETEROCHRONIC DEVELOPMENTAL PLASTICITY IN LARVAL SEA URCHINS AND ITS IMPLICATIONS FOR EVOLUTION OF NONFEEDING LARVAE

Preexisting developmental plasticity in feeding larvae may contribute to the evolutionary transition from development with a feeding larva to nonfeeding larval development. Differences in timing of development of larval and juvenile structures (heterochronic shifts) and differences in the size of the larval body (shifts in allocation) were produced in sea urchin larvae exposed to different amounts of food in the laboratory and in the field. The changes in larval form in response to food appear to be adaptive, with increased allocation of growth to the larval apparatus for catching food when food is scarce and earlier allocation to juvenile structures when food is abundant. This phenotypic plasticity among full siblings is similar in direction to the heterochronic evolutionary changes in species that have greater nutrient reserves within the ova and do not depend on particulate planktonic food. This similarity suggests that developmental plasticity that is adaptive for feeding larvae also contributes to correlated and adaptive evolutionary changes in the transition to nonfeeding larval development. If endogenous food supplies have the same effect on morphogenesis as exogenous food supplies, then changes in genes that act during oogenesis to affect nutrient stores may be sufficient to produce correlated adaptive changes in larval development.     

Comparative ungulate dynamics: the devil is in the detail

Attempts to relate species differences in population dynamics to variation in life histories rely on the assumption that the causes of contrasts in demography are sufficiently simple to be derived from first principles. Here, we investigate the causes of contrasts in dynamics between two ungulate populations on Hebridean islands (red deer and Soay sheep) and show that differences in stability, as well as in the effects of variation in density and climate, are related to differences in timing of reproduction relative to seasonal variation in resource abundance. In both populations, attempts to predict changes in population size sufficiently accurately for the results to be useful for management purposes require a knowledge of the responses of different age and sex categories to changes in density and climate, as well as of population structure.     

Domestication and the behavior-genetic analysis of captive populations

Captive environments are believed to produce behavioral changes in animal populations that may limit our ability to generalize back to natural populations. These behavioral changes are thought to be associated with one or both of the following: (a) changes in frequencies of genes or gene complexes due to the effects of inbreeding or to changes in selection pressure; (b) changes in development of the phenotype due to the effects of changes in environmental variables. Inbreeding leads to increase in homozygosity, that may result in developmental anomalies because of a breakdown in developmental homeostasis. Changes in selection pressure may disrupt coadapted gene complexes that have evolved in the wild. Often, domestication is believed to result in individuals that are “degenerate”; i.e. inferior to individuals in the wild. However, this notion has received no empirical support. In fact, if phenotype changes do occur under domestication, these are usually quantitative, not qualitative, in nature. We suggest that the study of the domestication process may reveal evolutionary principles that would be difficult to discover in other ways, and the zoological parks may be ideal situations for such research.     

Dynamics of the factors of 137Cs transfer to natural and sown grasses in the long term after the accident at the Chernobyl power plant

The regularities of changes in factors of 137Cs transfer to natural and sown grasses in the longterm period after the Chernobyl accident are described. The dynamics of changes in factors of 137Cs transfer to sown grasses over the period of 1993 to 1999 was of a non-uniform character. On average, these transfer factors (TF) tended to decrease in that period. A significant tendency for an increase in TF to sown grasses was noted for 1997-1999. The half-life periods of decrease in TF to natural grasses in the period 1993-1999 were shown to be ranged from 4.6 to 24.6 years. It was demonstrated that the differences in the TF dynamics between sown and natural grasses were related to the peculiarities of their development and application of countermeasures.     

The role of T56 in controlling the flexibility of the distal histidine in dehaloperoxidase-hemoglobin from Amphitrite ornata

The activation of dehaloperoxidase-hemoglobin (DHP) to form a ferryl intermediate requires the distal histidine, H55, to act as an acid base catalyst. The lack of ancillary amino acids in the distal pocket to assist in this process makes H55 even more important to the formation of active intermediates than in conventional peroxidases. Therefore, one can infer that the precise conformation H55 may greatly affect the enzymatic activity. Using site-direct mutagenesis at position T56, immediately adjacent to H55, we have confirmed that subtle changes in the conformation of H55 affect the catalytic efficiency of DHP. Mutating T56 to a smaller amino acid appears to permit H55 to rotate with relatively low barriers between conformations in the distal pocket, which may lead to an increase in catalytic activity. On the other hand, larger amino acids in the neighboring site appear to restrict the rotation of H55 due to the steric hindrance. In the case of T56V, which is an isosteric mutation, H55 appears less mobile, but forced to be closer to the heme iron than in wild type. Both proximity to the heme iron and flexibility of motion in some of the mutants can result in an increased catalytic rate, but can also lead to protein inactivation due to ligation of H55 to the heme iron, which is known as hemichrome formation. A balance of enzymatic rate and protein stability with respect to hemichrome formation appears to be optimum in wild type DHP (WT-DHP).     

Interactions of light and ethylene in hypocotyl hook maintenance in Arabidopsis thaliana seedlings

Etiolated seedlings frequently display a hypocotyl or epicotyl hook which opens on exposure to light. Ethylene has been shown to be necessary for maintenance of the hook in a number of plants in darkness. We investigated the interaction of ethylene and light in the regulation of hypocotyl hook opening in Arabidopsis thaliana . We found that hooks of Arabidopsis open in response to continuous red, far-red or blue light in the presence of up to 100 μl l⁻¹ ethylene. Thus a change in sensitivity to ethylene is likely to be responsible for hook opening in Arabidopsis, rather than a decrease in ethylene production in hook tissues. We used photomorphogenic mutants of Arabidopsis to demonstrate the involvement of both blue light and phytochrome photosensory systems in light-induced hook opening in the presence of ethylene. In addition we used ethylene mutants and inhibitors of ethylene action to investigate the role of ethylene in hook maintenance in seedlings grown in light and darkness.     

A Three-Tiered Study of Differences in Murine Intrahost Immune Response to Multiple Pneumococcal Strains

We apply a previously developed 4-variable ordinary differential equation model of in-host immune response to pneumococcal pneumonia to study the variability of the immune response of MF1 mice and to explore bacteria-driven differences in disease progression and outcome. In particular, we study the immune response to D39 strain of bacteria missing portions of the pneumolysin protein controlling either the hemolytic activity or complement-activating activity, the response to D39 bacteria deficient in either neuraminidase A or B, and the differences in the response to D39 (serotype 2), 0100993 (serotype 3), and TIGR4 (serotype 4) bacteria. The model accurately reproduces infection kinetics in all cases and provides information about which mechanisms in the immune response have the greatest effect in each case. Results suggest that differences in the ability of bacteria to defeat immune response are primarily due to the ability of the bacteria to elude nonspecific clearance in the lung tissue as well as the ability to create damage to the lung epithelium.     

Ethanol-induced increase in Fyn kinase activity in the dorsomedial striatum is associated with subcellular redistribution of protein tyrosine phosphatase α

In vivo exposure of rodents to ethanol leads to a long-lasting increase in Fyn kinase activity in the dorsomedial striatum (DMS). In this study, we set out to identify a molecular mechanism that contributes to the enhancement of Fyn activity in response to ethanol in the DMS. Protein tyrosine phosphatase α (PTPα) positively regulates the activity of Fyn, and we found that repeated systemic administration or binge drinking of ethanol results in an increase in the synaptic localization of PTPα in the DMS, the same site where Fyn resides. We also demonstrate that binge drinking of ethanol leads to an increase in Fyn activity and to the co-localization of Fyn and PTPα in lipid rafts in the DMS. Finally, we show that the level of tyrosine phosphorylated (and thus active) PTPα in the synaptic fractions is increased in response to contingent or non-contingent exposure of rats to ethanol. Together, our results suggest that the redistribution of PTPα in the DMS into compartments where Fyn resides is a potential mechanism by which the activity of the kinase is increased upon ethanol exposure. Such neuroadaptations could be part of a mechanism that leads to the development of excessive ethanol consumption.     

Using genetically engineered mice for radiation research

The laboratory mouse has been used for many decades as a model system for radiation research. Recent advances in genetic engineering now allow scientists to delete genes in specific cell types at different stages of development. The ability to manipulate genes in the mouse with spatial and temporal control opens new opportunities to investigate the role of genes in regulating the response of normal tissues and tumors to radiation. Currently, we are using the Cre-loxP system to delete genes, such as p53, in a cell-type specific manner in mice to study mechanisms of acute radiation injury and late effects of radiation. Our results demonstrate that p53 is required in the gastrointestinal (GI) epithelium to prevent radiation-induced GI syndrome and in endothelial and/or hematopoietic cells to prevent late effects of radiation. We have also used these genetic tools to generate primary tumors in mice to study tumor response to radiation therapy. These advances in genetic engineering provide a powerful model system to dissect both the mechanisms of normal tissue injury after irradiation and the mechanisms by which radiation cures cancer.     

The immunologic properties of Legionella cytolysin

Immunogenic properties of cytolysin were studied in experiments on guinea pigs. Preliminary immunization with cytolysin led to the suppression of response to ConA in lymphocytes not adhering to nylon wool and to the stimulation of response to Legionella antigens in lymphocytes adhering to nylon wool. For a month after infection with L. pneumophila the suppression of the proliferative activity of lymphocytes in the spleen of the immunized animals in response to ConA and Legionella antigens was observed, while in the lungs transitory suppression of response to ConA and Legionella antigens was followed by the restoration and then stimulation of proliferation in response to T-cell mitogen and specific antigens. The data obtained in these experiments indicate the capacity of cytolysin for modulating the development of immune response.     

Sexual dimorphism and synchrony of breeding: variation in polygyny potential among populations in the common brushtail possum, Trichosurus vulpecula

Male-biased sexual dimorphism in both size and body mass isa common characteristic of many polygynous mammals and is oftenattributed to sexual selection favoring large males. The degreeof dimorphism is thought to be related to the potential forsome males to monopolize access to estrous females, which isin turn related to the distribution of receptive females inspace and time. In the present study, we investigated the relationshipbetween the temporal distribution of breeding females and thedegree of mass dimorphism among 11 populations of the commonbrushtail possum from northern Australia. Breeding patternsvaried from complete aseasonality in some populations to a seasonalconcentration of births within 2 or 3 months in others. We predictedthat in populations in which mating opportunities were distributedthroughout the year, dominant males would be able to monopolizeaccess to larger numbers of estrous females than in populationsin which matings were more seasonal, and in such populations,large body size in males would be favored. We found that dimorphismwas related to seasonality of breeding, being greatest in populationswith a more aseasonal pattern. Mean body mass of male possumsalso decreased with increasing population density. Populationdensity may influence the degree of breeding synchrony withinpopulations, particularly in locations with a more seasonalclimate. The present study is the first to demonstrate plasticityin mass dimorphism in response to local variation in the synchronyof breeding in a mammal species.     

Respiration and microflora of the rhizosphere soil of wheat influenced by foliar application of urea

The numbers of micromycetes and bacteria were investigated with respect to oxygen consumption in the rhizosphere soil of wheat and in non-rhizosphere soil. Plants after foliar application of urea (2 % solution) and non-treated plants were cultivated in degraded chernozem and garden soil in a green-house. Changes in oxygen consumption by the suspensions of rhizosphere and non-rhizosphere soils corresponded to changes in the number of bacteria designated as the rhizosphere effect (R/S). Values of R/S depended on the presence of organic substrates. Changes in oxygen consumption by the soil suspension from the rhizosphere of wheat occurring due to foliar application of urea corresponded to changes in the amount of microflora. The results obtained are discussed with respect to a possible utilization of the data to follow metabolic activity of soils in a natural environment (in situ) determined according to oxygen consumption by a soil suspension, and to assess changes in the microflora of rhizosphere and non-rhizosphere soil.     

Influence of culture medium on the resistance and response of Mycobacterium bovis BCG to reactive nitrogen intermediates

The aim of the present work was to evaluate the influence of the culture medium on the resistance and response of Mycobacterium bovis BCG to reactive nitrogen intermediates, in vitro. BCG was grown in Sauton, Dubos or Middlebrook 7H9 medium and exposed to sodium nitroprusside (SNP) for up to 7 days. The percentage of bacilli that survived was significantly lower in Middlebrook 7H9 than in Sauton or Dubos medium. Addition of SNP to Middlebrook 7H9 caused an increase in the RedOx potential in either the absence or the presence of BCG, while addition of the compound to Sauton medium gave rise to an increase in the RedOx potential only in the absence of bacteria, whereas a decrease in the RedOx potential was observed in the presence of BCG. The resistance of BCG to SNP in the different media did not correlate with the concentration of peroxynitrite in culture supernatants. BCG grown in different media showed a differential protein expression pattern, as assessed by two-dimensional gel electrophoresis. Exposure of BCG to sub-lethal concentrations of SNP in Middlebrook 7H9, but not in Sauton medium, revealed a differential expression of at least 38 protein species. Altogether these results demonstrate that the growth medium may have a remarkable influence on the resistance and the response of BCG to SNP and suggest that the different resistance of BCG in the two media is unlikely to be due to a differential antioxidant effect of the medium itself.     

Effect of heterosexual olfactory and visual stimulation on 5-en-3 beta-hydroxysteroids and progesterone in the male rat brain

Pregnenolone, dehydroepiandrosterone and progesterone were measured in specific areas of the brain and in the retina of young adult male rats exposed to the scent or to the scent and view of young cycling females and compared to the levels obtained in males similarly exposed to other males (control). All the steroid values observed were much higher than those found in plasma, varied considerably from one area to another and responded sometimes in opposite directions to stimulation of young adult males by the scent or by the scent and view of cycling females. In male rats exposed to the scent of young cycling females pregnenolone decreased significantly only in the olfactory bulb in comparison with the controls. There were no significant changes in dehydroepiandrosterone or progesterone in this case. When male rats were exposed to the scent and view of female rats, pregnenolone again decreased significantly in the olfactory bulb while dehydroepiandrosterone increased significantly in the olfactory bulb and the retina and progesterone decreased significantly in the hypothalamus, amygdala and parietal cortex. These results are discussed in relation with a possible new role for certain steroids in neuroregulatory mechanisms related to behaviour.     

Heat shock mediated modulation of protein kinase CK2 in the nuclear matrix

Nuclear matrix, a key structure in the nuclear framework, appears to be a particularly responsive target during heat shock treatment of cells. We have previously shown that nuclear matrix is a preferential target for protein kinase CK2 signaling in the nucleus. The levels of CK2 in the nuclear matrix undergo dynamic changes in response to altered growth status in the cell. Here, we have demonstrated that CK2 targeting to the nuclear matrix is profoundly influenced by treatment of the cells to temperatures higher than 37 degrees C. Rapid increase in the nuclear matrix association of CK2 is observed when cells are placed at temperatures of 41 and 45 degrees C. This effect at 45 degrees C was higher than at 41 degrees C, and was time-dependent. Also, different cell lines behaved in a qualitatively similar manner though the quantitative responses differed. The modulations in the nuclear matrix associated CK2 in response to heat shock appear to be due to trafficking of the enzyme between cytosolic and nuclear compartments. In addition, it was noted that isolated nuclei subjected to heat shock also responded by a shuttling of the intrinsic CK2 to the nuclear matrix compartment. These results suggest that modulations in CK2 in the nuclear compartment in response to the heat stress occur not only by a translocation of the enzyme from the cytoplasmic compartment to the nuclear compartment, but also that there is a redistribution of the kinase within the nuclear compartment resulting in a preferential association with the nuclear matrix. The results support the notion that CK2 association with the nuclear matrix in response to heat shock may serve a protective role in the cell response to stress.