The nodule conductance to O<Subscript>2</Subscript> diffusion increases with high phosphorus content in the <Emphasis Type="Italic">Phaseolus vulgaris-</Emphasis>rhizobia symbiosis

Although recent studies have addressed the effects of phosphorus (P) deficiency on nodule O₂ permeability, little attention has been given to the relationship between nodule P status and nodule permeability. To study these traits, four recombinant inbred lines, namely RILs 34, 83, 115, 147 and one local variety (Concesa) of common bean (Phaseolus vulgaris) were inoculated with RhM11 (a native rhizobial strain from Haouz area of Marrakesh), and grown in hydroaeroponic culture under P-sufficiency (250 μmol P plant⁻¹ week⁻¹) versus P-deficiency (75 μmol P plant⁻¹ week⁻¹) conditions. At the flowering stage, the biomass of plants and nodules and their P contents was determined after measuring O₂ uptake by nodulated roots (Conr) and nodule conductance to O₂ diffusion (g_n). The results showed that P-deficiency significantly decreased plant growth and nodulation, though there were differences between bean genotypes. P-deficiency also induced a decrease in nodule P content (31%) in both sensitive (83, 147) and tolerant lines (34, 115), a 42 and 27% reduction in shoots of sensitive and tolerant lines, respectively. These decreases were associated with significant variations in nodule surface and O₂ permeability among bean genotypes and P-nutrition. Under P-deficiency, g_n increased more for the sensitive (39%) than for the tolerant lines (27%). This increase was linked with a rise both in the P levels in nodules and shoots, as well as in the efficiency of symbiotic nitrogen fixation as determined by nodule-dependent biomass production for the sensitive lines. Furthermore, positive correlations were found between O₂ permeability, g_n and P content both in nodules and shoots (r ² = 0.94** and r ² = 0.96**). We conclude that nodule variations in Conr and g_n are related to nodule P content, and may contribute to the adaptation of energy metabolism in N₂-fixing bean nodules to P-deficiency.     

Ethylenediamine- and propylenediaminediacetic acid derivatives as ligands for the “fac-[M(CO)3]” core (M = Re, Tc)

The reaction of Re(CO)₅Cl with o- or p-N-(nitrophenyl)ethylenediaminediacetic acid (H₂L¹, H₂L²) and o- or p-N-(nitrophenyl)propylenediaminediacetic acid (H₂L³, H₂L⁴) in methanol leads to the formation of stable anionic [Et₃NH][Re(CO)₃(L)] · H₂O complexes 1-4. These compounds have been characterized by means of IR, mass spectrometry, elemental analysis, NMR and conductimetry, as well as X-ray crystallography for 2 and 3. The [Re(CO)₃]⁺ moiety is coordinated via the nitrogen of the iminodiacetic acid unit and two oxygens of monodentate carboxylate groups. In each case, the nitro group of the aromatic ring remains uncoordinated. The analogous technetium-99m complexes 1′ and 3′ were also prepared quantitatively by the reaction of H₂L¹ and H₂L³, respectively, with the fac-[^99mTc(CO)₃(H₂O)₃]⁺ precursor in ethanol. The corresponding Re and ^99mTc compounds were shown to possess the same structure by means of HPLC studies. The high affinity of these ligands for the Tc(I) or Re(I) core, coupled with the easiness of their derivatization (by reduction of the nitro group in amino group), implies that the utilization of this ligand system to develop target-specific radiopharmaceuticals for diagnosis and therapy is promising.     

Detection of the Nav channel kdr-like mutation and modeling of factors affecting survivorship of Culex quinquefasciatus mosquitoes from six areas of Harris County (Houston), Texas,after permethrin field-cage tests

Culex quinquefasciatus is one of the most important mosquito vectors of arboviruses. Currently, the fastest approach to control disease transmission is the application of synthetic adulticide insecticides. However, in highly populated urban centers the development of insecticide resistance in mosquito populations could impair insecticide efficacy and therefore, disease control. To assess the effect of resistance on vector control, females of Cx. quinquefasciatus collected from six mosquito control operational areas in Harris County, Texas, were treated in field cage tests at three different distances with the pyrethroid Permanone^® 31–66 applied at the operational rate. Females were analyzed by sequencing and/or diagnostic PCR using de novo designed primers for detecting the kdr-like mutation in the voltage-gated sodium channel (L982F; TTA to TTT) (house fly kdr canonical mutation L1014F). Females from the Cx. quinquefasciatus susceptible Sebring strain and those from the six operational areas placed at 30.4 m from the treatment source were killed in the tests, while 14% of field-collected mosquitoes survived at 60.8 m, and 35% at 91.2 m from the source. The diagnostic PCR had a with 97.5% accuracy to detect the kdr-like mutation. Pyrethroid resistant mosquitoes carrying the L982F mutation were broadly distributed in Harris County at high frequency. Among mosquitoes analyzed (n = 1,028), the kdr-kdr genotype was prevalent (81.2%), the kdr-s genotype was 18%, and s-s mosquitoes were less than 1% (n = 8). A logistic regression model estimated an equal probability of survival for the genotypes kdr-kdr and kdr-s in all areas analyzed. Altogether, our results point to a high-risk situation for the pyrethroid-based arboviral disease control in Harris County.     

Influence of NaCl-salinity on growth,photosynthesis, water relations and solute accumulation in <Emphasis Type="Italic">Phragmites australis</Emphasis>

The aim of this study was to investigate the effects of NaCl-salinity on the physiological attributes in common reed, Phragmites australis (Cav.) Trin. ex Steudel. Plants grew optimally under salinity treatment with standard nutrient solution without added salt and at NaCl concentrations up to 100 mM. Applied for 21 days, NaCl-salinity (300 and 500 mM) caused a significant reduction in growth allocation of all different tissues of P. australis. Shoot growth of reed plants displayed a highly significant correlation with plant–water relations and photosynthetic parameters. The net photosynthetic rate and stomatal conductance of reed plants treated with NaCl-salinity at varying osmotic potential (ψ_π) of nutrient solutions were positively correlated, and the former variable also had a strong positive relationship with transpiration rate. Leaf water potential and ψ_π followed similar trends and declined significantly as ψ_π of watering solutions was lowered. The increase in total inorganic nutrients resulting from increased Na⁺ and Cl⁻ in all tissues and K⁺, Ca²⁺ and Mg²⁺ concentrations were maintained even at the most extreme salt concentration. Common reed exhibited high K⁺/Na⁺ and Ca²⁺/Na⁺ selectivity ratios over a wide range of salinities under NaCl-salinity. These findings suggest that reed plants were able to adapt well to high salinities by lowering their leaf ψ_π and the adjustment of osmotically active solutes in the leaves.     

Purification and characterization of a low molecular weight cysteine proteinase inhibitor from bovine muscle

A low-Mr tight binding proteinase inhibitor was purified from bovine muscle by alkaline denaturation of cysteine proteinases, gel filtration on Sephadex G-75 and affinity chromatography on carboxymethyl-papain-Sepharose. Chromatofocusing separated three isoforms which are similar in their Mr of about 14 000, their stability with heating at 80 degrees C and their inhibitory activity towards cathepsin H, cathepsin B and papain. The equilibrium constants (Ki) were determined for these three cysteine proteinases but for cathepsin H, association (kass) and dissociation (kdiss) rate constants were also evaluated. Ki values of 56 nM and 8.4 nM were found for cathepsin B and cathepsin H, respectively. For papain, Ki was in the range of 0.1-1 nM. The kinetic features of enzyme-inhibitor binding suggest a possible role for this low-Mr protein inhibitor in controlling 'in vivo' cathepsin H proteolytic activity. With regard to cathepsin B, such a physiological role was less evident.     

Influence of denervation on the regeneration of Pleurodele limbs

Abstract. A cytophotometric study of Feulgen-stained mesenchymal cell nuclei from regeneration blastemas of both innervated and denervated limbs over the 1st 7 days following the midbud stage showed a diminution of the percentage of cells in the S + G₂ phases and a corresponding augmentation of the percentage of cells in the G₀+ G₁ phases. This change, which was temporally correlated with the redifferentiation of the innervated blastemas, was greater in denervated blastemas, even though they do not redifferentiate. From these results, it is concluded that the denervation of midbud blastemas brings about either an extension of the G₁ phase or an exiting from the cell cycle to G₁ (G_0–1), or both phenomena.     

Hydroponics versus field lysimeter studies of urea, ammonium and nitrate uptake by oilseed rape(Brassica napus L.)

N-fertilizer use efficiencies are affected by their chemical composition and suffer from potential N-losses by volatilization. In a field lysimeter experiment, (15)N-labelled fertilizers were used to follow N uptake by Brassica napus L. and assess N-losses by volatilization. Use of urea with NBPT (urease inhibitor) showed the best efficiency with the lowest N losses (8% of N applied compared with 25% with urea alone). Plants receiving ammonium sulphate, had similar yield achieved through a better N mobilization from vegetative tissues to the seeds, despite a lower N uptake resulting from a higher volatilization (43% of applied N). Amounts of (15)N in the plant were also higher when plants were fertilized with ammonium nitrate but N-losses reached 23% of applied N. In parallel, hydroponic experiments showed a deleterious effect of ammonium and urea on the growth of oilseed rape. This was alleviated by the nitrate supply, which was preferentially taken up. B. napus was also characterized by a very low potential for urea uptake. BnDUR3 and BnAMT1, encoding urea and ammonium transporters, were up-regulated by urea, suggesting that urea-grown plants suffered from nitrogen deficiency. The results also suggested a role for nitrate as a signal for the expression of BnDUR3, in addition to its role as a major nutrient. Overall, the results of the hydroponic study showed that urea itself does not contribute significantly to the N nutrition of oilseed rape. Moreover, it may contribute indirectly since a better use efficiency for urea fertilizer, which was further increased by the application of a urease inhibitor, was observed in the lysimeter study.     

Computed Tomography (CT) Scanning Facilitates Early Identification of Neonatal Cystic Fibrosis Piglets

Background

Cystic Fibrosis (CF) is the most prevalent autosomal recessive disease in the Caucasian population. A cystic fibrosis transmembrane conductance regulator knockout (CFTR-/-) pig that displays most of the features of the human CF disease has been recently developed. However, CFTR ^-/- pigs presents a 100% prevalence of meconium ileus that leads to death in the first hours after birth, requiring a rapid diagnosis and surgical intervention to relieve intestinal obstruction. Identification of CFTR ^-/- piglets is usually performed by PCR genotyping, a procedure that lasts between 4 to 6 h. Here, we aimed to develop a procedure for rapid identification of CFTR ^-/- piglets that will allow placing them under intensive care soon after birth and immediately proceeding with the surgical correction.

Methods and Principal Findings

Male and female CFTR ^+/- pigs were crossed and the progeny was examined by computed tomography (CT) scan to detect the presence of meconium ileus and facilitate a rapid post-natal surgical intervention. Genotype was confirmed by PCR. CT scan presented a 94.4% sensitivity to diagnose CFTR ^-/- piglets. Diagnosis by CT scan reduced the birth-to-surgery time from a minimum of 10 h down to a minimum of 2.5 h and increased the survival of CFTR ^-/- piglets to a maximum of 13 days post-surgery as opposed to just 66 h after later surgery.

Conclusion

CT scan imaging of meconium ileus is an accurate method for rapid identification of CFTR ^-/- piglets. Early CT detection of meconium ileus may help to extend the lifespan of CFTR ^-/- piglets and, thus, improve experimental research on CF, still an incurable disease.     

Structure of betaine aldehyde dehydrogenase at 2.1 A resolution.

The three-dimensional structure of betaine aldehyde dehydrogenase, the most abundant aldehyde dehydrogenase (ALDH) of cod liver, has been determined at 2.1 A resolution by the X-ray crystallographic method of molecular replacement. This enzyme represents a novel structure of the highly multiple ALDH, with at least 12 distinct classes in humans. This betaine ALDH of class 9 is different from the two recently determined ALDH structures (classes 2 and 3). Like these, the betaine ALDH structure has three domains, one coenzyme binding domain, one catalytic domain, and one oligomerization domain. Crystals grown in the presence or absence of NAD+ have very similar structures and no significant conformational change occurs upon coenzyme binding. This is probably due to the tight interactions between domains within the subunit and between subunits in the tetramer. The oligomerization domains link the catalytic domains together into two 20-stranded pleated sheet structures. The overall structure is similar to that of the tetrameric bovine class 2 and dimeric rat class 3 ALDH, but the coenzyme binding with the nicotinamide in anti conformation, resembles that of class 2 rather than of class 3.