Chiral separation of novel iminonaringenin derivatives

A series of 4‐iminonaringenin derivatives 2 ‐ 6 have been prepared in good overall yields from a condensation reaction between naringenin and primary amines. The structures of all products were confirmed by ultraviolet, infrared, proton nuclear magnetic resonance, and carbon‐13 nuclear magnetic resonance spectroscopic techniques. These derivatives were analyzed by high‐performance liquid chromatography using polysaccharide‐based chiral stationary phases, namely, Chiralpak IB and Chiralcel OD, using various mobile phases. 2‐Propanol showed a high enantioselectivity for naringin and its derivatives using achiral column containing immobilized polysaccharides (Chiralpak IB).     

Changes in hydraulic conductivity, mechanical properties, and density reflecting the fall in strain along the lateral roots of two species of tropical trees

Roots have been described as having larger vessels and so greater hydraulic efficiency than the stem. Differences in the strength and stiffness of the tissue within the root system itself are thought to be an adaptation to the loading conditions experienced by the roots and to be related to differences in density. It is not known how potential mechanical adaptations may affect the hydraulic properties of the roots. The change in strength, stiffness, conductivity, density, sapwood area, and second moment of area distally along the lateral roots of two tropical tree species in which the strain is known to decrease rapidly was studied and the values were compared with those of the trunk. It was found that as the strain fell distally along the roots, so did the strength and stiffness of the tissue, whereas the conductivity increased exponentially. These changes appeared to be related to differences in density. In contrast to the distal-most roots, the tissue of the proximal roots had a lower conductivity and higher strength than that of the trunk. This suggests that mechanical requirements on the structure rather than the water potential gradient from roots to branches are responsible for the general pattern that roots have larger vessels than the stem. In spite of their increased transectional area, the buttressed proximal roots were subjected to higher levels of stress and had a lower total conductivity than the rest of the root system.     

The gravitropic response of poplar trunks: key roles of prestressed wood regulation and the relative kinetics of cambial growth versus wood maturation

In tree trunks, the motor of gravitropism involves radial growth and differentiation of reaction wood (Archer, 1986). The first aim of this study was to quantify the kinematics of gravitropic response in young poplar (Populus nigra x Populus deltoides, 'I4551') by measuring the kinematics of curvature fields along trunks. Three phases were identified, including latency, upward curving, and an anticipative autotropic decurving, which has been overlooked in research on trees. The biological and mechanical bases of these processes were investigated by assessing the biomechanical model of Fournier et al. (1994). Its application at two different time spans of integration made it possible to test hypotheses on maturation, separating the effects of radial growth and cross section size from those of wood prestressing. A significant correlation between trunk curvature and Fournier's model integrated over the growing season was found, but only explained 32% of the total variance. Moreover, over a week's time period, the model failed due to a clear out phasing of the kinetics of radial growth and curvature that the model does not take into account. This demonstrates a key role of the relative kinetics of radial growth and the maturation process during gravitropism. Moreover, the degree of maturation strains appears to differ in the tension woods produced during the upward curving and decurving phases. Cell wall maturation seems to be regulated to achieve control over the degree of prestressing of tension wood, providing effective control of trunk shape.     

How to determine sapling buckling risk with only a few measurements

Tree buckling risk (actual height/critical buckling height) is an important biomechanical trait of plant growth strategies, and one that contributes to species coexistence. To estimate the diversity of this trait among wide samples, a method that minimizes damage to the plants is necessary. On the basis of the rarely used, complete version of Greenhill's model (1881, Proceedings of the Cambridge Philosophical Society 4(2): 65-73), we precisely measured all the necessary parameters on a sample of 236 saplings of 16 species. Then, using sensitivity (variance) analysis, regressions between successive models for risk factors and species ranks and the use of these models on samples of self- and nonself-supporting saplings, we tested different degrees of simplification up to the most simple and widely used formula that assumes that the tree is a cylindrical homogeneous pole. The size factor had the greatest effect on buckling risk, followed by the form factor and the modulus of elasticity of the wood. Therefore, estimates of buckling risk must consider not only the wood properties but especially the form factor. Finally, we proposed a simple but accurate method of assessing tree buckling risk that is applicable to a wide range of samples and that requires mostly nondestructive measurements.     

A fluorescence-based helicase assay: application to the screening of G-quadruplex ligands

Helicases, enzymes that unwind DNA or RNA structure, are present in the cell nucleus and in the mitochondrion. Although the majority of the helicases unwind DNA or RNA duplexes, some of these proteins are known to resolve unusual structures such as G-quadruplexes (G4) in vitro. G4 may form stable barrier to the progression of molecular motors tracking on DNA. Monitoring G4 unwinding by these enzymes may reveal the mechanisms of the enzymes and provides information about the stability of these structures. In the experiments presented herein, we developed a reliable, inexpensive and rapid fluorescence-based technique to monitor the activity of G4 helicases in real time in a 96-well plate format. This system was used to screen a series of G4 structures and G4 binders for their effect on the Pif1 enzyme, a 5′ to 3′ DNA helicase. This simple assay should be adaptable to analysis of other helicases and G4 structures.     

Application of modular response analysis to medium- to large-size biological systems

The development of high-throughput genomic technologies associated with recent genetic perturbation techniques such as short hairpin RNA (shRNA), gene trapping, or gene editing (CRISPR/Cas9) has made it possible to obtain large perturbation data sets. These data sets are invaluable sources of information regarding the function of genes, and they offer unique opportunities to reverse engineer gene regulatory networks in specific cell types. Modular response analysis (MRA) is a well-accepted mathematical modeling method that is precisely aimed at such network inference tasks, but its use has been limited to rather small biological systems so far. In this study, we show that MRA can be employed on large systems with almost 1,000 network components. In particular, we show that MRA performance surpasses general-purpose mutual information-based algorithms. Part of these competitive results was obtained by the application of a novel heuristic that pruned MRA-inferred interactions a posteriori. We also exploited a block structure in MRA linear algebra to parallelize large system resolutions.     

Chitinolytic actinobacteria isolated from an Algerian semi-arid soil: development of an antifungal chitinase-dependent assay and GH18 chitinase gene identification

The purpose of this study was to explore the microbial potential of a semi-arid sandy soil from south-central Algeria in order to isolate new chitinolytic actinobacteria. This soil is subjected to high temperatures (up to 43 °C) and has low nutrient content. Strains were isolated by plating soil suspensions on Bennett and Colloidal Chitin (CCM) medium. An initial clustering of isolates was made through BOX-PCR genetic profiling. Next, a 16S rRNA gene sequencing of representative isolates was realized. We also identified optimum physicochemical conditions for chitinolytic activity. A rapid in vitro assay based on glucose catabolic repression was developed to select isolates having a chitinase-dependent antifungal activity against two phytopathogenic fungi. Gene identification of glycosyl hydrolase family 18 (GH18) permitted us to assess the divergence of chitinase genes. Forty isolates were obtained from the semi-arid sandy soil. The molecular identification permitted us to assign them to Streptomyces or Micromonospora genera with seven possibly new bacterial species. For chitinolytic activity, 100% of isolates were able to grow and degrade colloidal chitin at pH 7 and at a temperature ranging from 30 to 40 °C. We also observed that Micromonospora strains had atypical activity patterns, with a strong chitinase activity maintained at high temperature. Finally, three strains presented an interesting chitinolytic potential to reduce fungal growth with new GH18 sequences. This study presents a new rapid method to detect antifungal chitinase-dependent activity that allowed to identify potentially new species of actinobacteria and new GH18 gene sequences.     

Intragenic deletion patterns of dystrophin gene in Duchenne and Becker muscular dystrophy patients from Algeria

Duchenne and Becker muscular dystrophies (DMD and BMD) represent the most frequent neuromuscular diseases in humans (1/3,500–6,000 live male births), characterized by an X-linked recessive pattern of inheritance and therefore affecting mainly male individuals. DMD and BMD are allelic disorders resulting from genetic defects, mostly intragenic deletions, in the dystrophin gene. Using multiplex polymerase chain reaction (PCR), we have analyzed 170 male patients from unrelated families originating from Algeria, showing that 68 % of them harbored deletion events affecting the known 5′ or 3′ hot spot regions. The distal portion was predominantly involved (85 %), whereas 37 distinctive patterns of deletion were identified in our panel. The extent of deletion varied from 1 to 32 exons, although the average number was about four exons. The lack of seven exons (45, 46, 47, 48, 50, 51 and 52), each alone or in combination, represented about 78 % of the alterations encountered, while exon 48 was most frequently involved (50 %). The effect of the deletions showed that the reading frame rule proved mostly true, correlating with the clinical diagnosis suggested. Moreover, the c.525delT mutation in the γ-sarcoglycan gene was present in non-deleted patients (7 %), suggesting that clinical features can still be misleading. Finally, multiplex PCR proved to be a simple, fast and low-cost approach for the molecular diagnosis of dystrophinopathies in Algeria, whereas our data could contribute to the creation of a national registry of DMD/BMD patients in our country, which would give them hope to an access to already available genotype-based therapies.     

Chronic Inhibition of Dopamine β-Hydroxylase Facilitates Behavioral Responses to Cocaine in Mice

The anti-alcoholism medication, disulfiram (Antabuse), decreases cocaine use in humans regardless of concurrent alcohol consumption and facilitates cocaine sensitization in rats, but the functional targets are unknown. Disulfiram inhibits dopamine β-hydroxylase (DBH), the enzyme that converts dopamine (DA) to norepinephrine (NE) in noradrenergic neurons. The goal of this study was to test the effects of chronic genetic or pharmacological DBH inhibition on behavioral responses to cocaine using DBH knockout (Dbh −/−) mice, disulfiram, and the selective DBH inhibitor, nepicastat. Locomotor activity was measured in control (Dbh +/−) and Dbh −/− mice during a 5 day regimen of saline+saline, disulfiram+saline, nepicastat+saline, saline+cocaine, disulfiram+cocaine, or nepicastat+cocaine. After a 10 day withdrawal period, all groups were administered cocaine, and locomotor activity and stereotypy were measured. Drug-naïve Dbh −/− mice were hypersensitive to cocaine-induced locomotion and resembled cocaine-sensitized Dbh +/− mice. Chronic disulfiram administration facilitated cocaine-induced locomotion in some mice and induced stereotypy in others during the development of sensitization, while cocaine-induced stereotypy was evident in all nepicastat-treated mice. Cocaine-induced stereotypy was profoundly increased in the disulfiram+cocaine, nepicastat+cocaine, and nepicastat+saline groups upon cocaine challenge after withdrawal in Dbh +/− mice. Disulfiram or nepicastat treatment had no effect on behavioral responses to cocaine in Dbh −/− mice. These results demonstrate that chronic DBH inhibition facilitates behavioral responses to cocaine, although different methods of inhibition (genetic vs. non-selective inhibitor vs. selective inhibitor) enhance qualitatively different cocaine-induced behaviors.