The effects of gibberellic acid upon developmental processes in Drosophila hydei

The injection of gibberellic acid (GA₃) into larvae of Drosophila hydei can affect the pattern of gene activities in a specific manner. This became clear from a study on the pattern of puffs in the giant chromosomes of the larval salivary glands.Depending upon the age of the larvae injected, either of two new puffs, 72B or 21B, appeared. Not only was the activity of these chromosome regions stimulated but the activity of some normally occurring puffs specific for the period shortly before puparium formation was affected. If GA₃ was injected during the period shortly before puparium formation further development became influenced as revealed by a significant reduction in the number of flies emerging from treated animals.

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Zusammenfassung Es wurde die Wirkung verschiedener Konzentrationen von Gibberellinsäure (GA₃) nach Injektion in Drosophila-Larven unterschiedlichen Alters untersucht. Konzentrationen von 3 g/Larve und höher führten bei jungen und mittleren Larven des 3. Stadiums zur Ausbildung eines neuen Puffs (72B) in den polytänen Chromosomen der Speicheldrüse. Diese Reaktion wurde in 15–20% der Larven beobachtet.In späteren Stadien der Entwicklung kurz vor der Pupariumbildung wird nach Injektion von 1 g/Larve ein weiterer Puff (21B) in 10% der Larven induziert. Der Prozentsatz der Larven die diesen Puff 3 Stunden nach der Injektion aufweisen, nimmt mit steigender GA₃-Konzentration zu. Nach Injektion von 5–6 g/Larve war der Puff 21B in 80% der Tiere enthalten.Zur selben Zeit ließ sich eine Beinflussing der Aktivität von zwei Puffs nachweisen, die für die Periode der Pupariumbildung spezifisch sind. Die Aktivität dieser Puffs wird durch die Injektion von GA₃ herabgesetzt.GA₃ bewirkt nicht nur die Induktion neuer Puffs, sondern außerdem eine Verzögerung der Entwicklung. Nach der Injektion von 2 g/Larve verzögert sich die Zeit der Pupariumbildung um 2–10 Stunden. Die Zahl der Fliegen, die aus Larven schlüpfte, die kurz vor der Pupariumbildung eine Injektion von mehr als 3 g GA₃ erhielten, war deutlich herabgesetzt. Es wird vermutet, daß GA₃ eine spezifische Wirkung auf die Aktivität des Genoms ausübt und damit eine Beeinflussung der normalen Entwicklung bewirkt.

     

No influence of number of donor CFU-GM on granulocyte recovery in bone marrow transplantation for acute leukemia

The possible interrelation between infused bone marrow CFU-GM and peripheral granulocyte recovery was studied in 16 patients transplanted for acute leukemia. The influence of several clinical events that could modify the graft fate were also analysed. Our results show that: 1) There was no correlation between the number of infused nucleated cells and granulocyte recovery. 2) There was no correlation between the number of infused CFU-GM and granulocyte regeneration. 3) There were significant differences between the day of engraftment in patients with clinically documented HSV infection compared to patients without infection.     

Chromosomal DNA denaturation and reassociation in situ.

The degree of chromosomal DNA (cDNA) denaturation and renaturation on polytene chromosomes has been measured by UV microspectrophotometry. Also DNA losses occurring upon denaturation have been quantified by Feulgen, gallocyanin-chromalum and UV. It has been observed that denaturation in alkali (0.07 N NaOH at room temperature) and formamide (90% formamide; 0.1 SSC, pH 7.2) at 65 °C removes about 30% of the DNA. Low DNA loss occurs upon denaturation in HCl (0.24 M) at room temperature and 60% formamide: 2 × 10^?4 M EDTA (pH 8) at 55 °C. The presence of 4% formaldehyde in the denaturation buffer prevents DNA loss. After denaturation of chromosomes in 0.1 × SSC containing 4% formaldehyde at 100 °C for 30 sec, an hyperchromicity of 39 °C is observed. The denaturation efficiency varies with the denaturation treatment. The percentage reassociation was measured from the difference in the UV absorption of renatured chromosomes and that of denatured chromosomes from the same set. It seems that in our conditions DNA:DNA reassociation does not occur. The efficiency of hybridization is proportional to the denaturation extent of the DNA. However, the entire fraction of DNA which has been denatured is not available for hybridization.     

Comparative study of immunobiological activities ofPseudomonas aeruginosa andBrucella melitensis lipopolysaccharides

The toxic activity ofBrucella melitensis andPseudomonas aeruginosa lipopolysaccharides as well as their behavior as immunogens, mitogens, and interferon inducers have been studied. Although their toxicities were very similar, the former molecule was incapable of eliciting a primary immune response in mice. Rabbit hyperimmunization gave titers half of those obtained withP. aeruginosa lipopolysaccharide. Optimal mitogenic responses of spleen cell cultures were obtained using 10–50 μg/ml and 50–100 μg/ml ofPseudomonas andBrucella lipopolysaccharide, respectively, giving the latter a lower stimulation of³H-thymidine uptake. Interferon titers induced in chickens byBrucella lipopolysaccharide were three times lower than those obtained withPseudomonas lipopolysaccharide.     

In vitro antileishmanial and cytotoxic activities of nerolidol are associated with changes in plasma membrane dynamics

The sesquiterpene nerolidol is a membrane-active compound that has demonstrated antitumor, antibacterial, antifungal and antiparasitic activities. In this study, we used electron paramagnetic resonance (EPR) spectroscopy and biophysical parameters determined via cell culture assays to study the mechanisms underlying the in vitro antileishmanial activity of nerolidol. The EPR spectra of a spin-labeled stearic acid indicated notable interactions of nerolidol with the cell membrane of Leishmania amazonensis amastigotes. The nerolidol IC₅₀ values in L. amazonensis amastigotes and promastigotes were found to depend on the cell concentration used in the assay. This dependence was described by an equation that considers various cell suspension parameters, such as the 50% inhibitory concentrations of nerolidol in the cell membrane (c_m50) and the aqueous phase (c_w50) and the membrane-water partition coefficient of nerolidol (K_M/W). Via cytotoxicity (CC₅₀) and hemolytic potential (HC₅₀) data, these parameters were also determined for nerolidol in macrophages and erythrocytes. With a c_w50 of 125 μM, macrophages were less sensitive to nerolidol than amastigotes and promastigotes, which had mean c_w50 values of 56 and 74 μM, respectively. The estimated c_m50 values of nerolidol for amastigotes and promastigotes and macrophages were between 2.6 and 3.0 M, indicating substantial accumulation of nerolidol in the cell membrane. In addition, the spin-label EPR data indicated that membrane dynamic changes occurred in L. amazonensis amastigotes at concentrations similar to the nerolidol IC₅₀ value.     

Effects of litter mixing on litter decomposition and soil properties along simulated invasion gradients of non-native trees

Plant and Soil - Phosphorus (P) is an essential macronutrient with major impacts on global crop productivity. Recent work showed that chlorophyll a fluorescence analysis can be used as a sensitive...     

A hierarchical Bayesian Beta regression approach to study the effects of geographical genetic structure and spatial autocorrelation on species distribution range shifts

Global climate change (GCC) may be causing distribution range shifts in many organisms worldwide. Multiple efforts are currently focused on the development of models to better predict distribution range shifts due to GCC. We addressed this issue by including intraspecific genetic structure and spatial autocorrelation (SAC) of data in distribution range models. Both factors reflect the joint effect of ecoevolutionary processes on the geographical heterogeneity of populations. We used a collection of 301 georeferenced accessions of the annual plant Arabidopsis thaliana in its Iberian Peninsula range, where the species shows strong geographical genetic structure. We developed spatial and nonspatial hierarchical Bayesian models (HBMs) to depict current and future distribution ranges for the four genetic clusters detected. We also compared the performance of HBMs with Maxent (a presence‐only model). Maxent and nonspatial HBMs presented some shortcomings, such as the loss of accessions with high genetic admixture in the case of Maxent and the presence of residual SAC for both. As spatial HBMs removed residual SAC, these models showed higher accuracy than nonspatial HBMs and handled the spatial effect on model outcomes. The ease of modelling and the consistency among model outputs for each genetic cluster was conditioned by the sparseness of the populations across the distribution range. Our HBMs enrich the toolbox of software available to evaluate GCC‐induced distribution range shifts by considering both genetic heterogeneity and SAC, two inherent properties of any organism that should not be overlooked.     

Difference in reproductive mode rather than ploidy explains niche differentiation in sympatric sexual and apomictic populations of Potentilla puberula

Apomicts tend to have larger geographical distributional ranges and to occur in ecologically more extreme environments than their sexual progenitors. However, the expression of apomixis is typically linked to polyploidy. Thus, it is a priori not clear whether intrinsic effects related to the change in the reproductive mode or rather in the ploidy drive ecological differentiation. We used sympatric sexual and apomictic populations of Potentilla puberula to test for ecological differentiation. To distinguish the effects of reproductive mode and ploidy on the ecology of cytotypes, we compared the niches (a) of sexuals (tetraploids) and autopolyploid apomicts (penta‐, hepta‐, and octoploids) and (b) of the three apomictic cytotypes. We based comparisons on a ploidy screen of 238 populations along a latitudinal transect through the Eastern European Alps and associated bioclimatic, and soil and topographic data. Sexual tetraploids preferred primary habitats at drier, steeper, more south‐oriented slopes, while apomicts mostly occurred in human‐made habitats with higher water availability. Contrariwise, we found no or only marginal ecological differentiation among the apomictic higher ploids. Based on the pronounced ecological differences found between sexuals and apomicts, in addition to the lack of niche differentiation among cytotypes of the same reproductive mode, we conclude that reproductive mode rather than ploidy is the main driver of the observed differences. Moreover, we compared our system with others from the literature, to stress the importance of identifying alternative confounding effects (such as hybrid origin). Finally, we underline the relevance of studying ecological parthenogenesis in sympatry, to minimize the effects of differential migration abilities.     

Photoinhibition,photo-ecophysiology,and biophysics,a special issue in honor of Wah Soon Chow

Photosynthesis Research - Abnormally altered precipitation patterns induced by climate change have profound global effects on crop production. However, the plant functional responses to various...