Atx1-like chaperones and their cognate P-type ATPases: copper-binding and transfer

Copper is an essential yet toxic metal ion. To satisfy cellular requirements, while, at the same time, minimizing toxicity, complex systems of copper trafficking have evolved in all cell types. The best conserved and most widely distributed of these involve Atx1-like chaperones and P_1B-type ATPase transporters. Here, we discuss current understanding of how these chaperones bind Cu(I) and transfer it to the Atx1-like N-terminal domains of their cognate transporter.     

The assessment of total energy expenditure of female farmers under field conditions.

The paper reviews methods, and their difficulties, in the measurement of the daily energy expenditure of rural women under field conditions in developing countries. Since all methods need to be validated against a reference method which is usually based on indirect calorimetry, examples of the use of this technique are given. The energy costs of most agricultural and daily tasks of rural women in developing countries have been measured. Large intra- and inter-individual variations in the cost of a single activity occur, so repeated measurements are needed to obtain a valid mean energy cost for a specific activity for a homogeneous group of individuals. Much work remains to be done on the assessment of the duration and the intensity of the physical activity of the rural adolescent and adult female population. Studies indicate that the workload of most rural women in developing countries is excessive and frequently associated with acute poverty.     

Acclimatation sur la côte d'azur et en corse deSerangium parcesetosum [Col.: Coccinellidae] prédateur de l'aleurode des citrus,Dialeurodes citri [Hom.: Aleyrodidae]

Résumé La CoccinelleSerangium parcesetosum Sicard originaire de l'Inde a été importée en France en 1985 de Géorgie soviétique où elle avait été introduite pour lutter contre l'Aleurode des CitrusDialeurodes citri Ashmead. Les premiers lachers ont été effectués sur la C?te d'Azur et en Corse où elle semble désormais bien acclimatée.      

Relationship of endogenous abscisic Acid to sucrose level and seed growth rate of soybeans

It has been proposed that abscisic acid (ABA) may stimulate sucrose transport into filling seeds of legumes, potentially regulating seed growth rate. The objective of this study was to determine whether the rate of dry matter accumulation in seeds of soybeans (Glycine max L.) is correlated with the endogenous levels of ABA and sucrose in those sinks. The levels of ABA and sucrose in seed tissues were compared in nine diverse Plant Introduction lines having seed growth rates ranging from 2.5 to 10.0 milligrams dry weight per seed per day. At 14 days after anthesis (DAA), seeds of all genotypes contained less than 2 micrograms of ABA per gram fresh weight. Levels of ABA increased rapidly, however, reaching maxima at 20 to 30 DAA, depending upon tissue type and genotype. ABA accumulated first in seed coats and then in embryos, and ABA maxima were higher in seed coats (8 to 20 micrograms per gram fresh weight) than in embryos (4 to 9 micrograms per gram fresh weight. From 30 to 50 DAA, ABA levels in both tissues decreased to less than 2 micrograms per gram fresh weight. Levels of sucrose were also low early in development, less than 10 milligrams per gram fresh weight at 14 DAA. However, by 30 DAA, sucrose levels in seed coats had increased to 20 milligrams per gram fresh weight and remained fairly constant for the remainder of the filling period. In contrast, sucrose accumulated in embryos throughout the filling period, reaching levels greater than 40 milligrams per gram fresh weight by 50 DAA. Correlation analyses indicated that the level of ABA in seed coats and embryos was not directly correlated to the level of sucrose measured in those tissues or to the rate of seed dry matter accumulation during the linear filling period. Rather, the ubiquitous pattern of ABA accumulation early in development appeared to coincide with water uptake and the rapid expansion of cotyledons occurring at that time. Whole tissue sucrose levels in embryos and seed coats, as well as sucrose levels in the embryo apoplast, were generally not correlated with the rate of dry matter accumulation. Thus, it appears that, in this set of diverse soybean genotypes, seed growth rate was not limited by endogenous concentrations of ABA or sucrose in reproductive tissues.     

Nucleotide sequence of a Xenopus laevis mitochondrial DNA fragment containing the D-loop, flanking tRNA genes and the apocytochrome b gene

Extensive corrections of the nucleotide sequence of the Xenopus laevis mitochondrial (mt) displacement (D) loop and surrounding genes [Wong et al., Nucl. Acids Res. 11 (1983) 4977-4995] are reported, including addition of two stretches of nucleotides and 60 scattered modifications. The additional sequences presented here correspond to the apocytochrome b gene, the tRNAGlu gene and part of URF6. This allows us to propose a conformational model for the X. laevis apocytochrome b protein and also permits comparisons with mammalian mtDNA. The D-loop sequence is poorly conserved except for sequences involved in the regulation of the mt genome (conserved sequence blocks and the DNA polymerase stop sequences). On the other hand, all genes show marked conservation both of their nucleotide sequence and their respective location on the mt genome. Organization of the genetic information described for mammalian mtDNA also holds for the X. laevis mtDNA. This result strongly suggests that all animal vertebrate mtDNAs have followed the same evolutionary pathway.     

Vigilant Behaviour: Predictability or Randomness? Spectral Analysis of Series of Scan Durations and their Relationship with Inter-scan Intervals

While feeding, many animals frequently look up and visually scan their environment. Using spectral analysis of continuous series of scan durations from a purple sandpiper Calidris maritima and Barbary doves Streptopelia risoria, we show that there are sequential non-random patterns and significant periodicities in all the examined series such that the birds cycled regularly between short and long scans. The cycles are comparable to those for the continuous series of inter-scan intervals of the same behavioural sequences. We suggest a re-examination of the functional costs and benefits of instantaneous randomness versus sequential predictability in alternating between feeding and scanning and a revision of the models of the way animals alternate between these behaviour patterns.     

In vitro influence of zinc and magnesium on the deformability of red blood cells artificially hardened by heating

Trace elements have been shown to improve red blood cell (RBC) deformability: zinc in sickle cell disease and magnesium in an in vitro model of chemically rigidified erythrocytes. In this study, we investigated the effect and the influence of incubation time of zinc or magnesium on an in vitro model of rigidified RBCs by heating. Erythrocyte rigidity was determined by viscosimetry at high shear rate by a falling ball viscosimeter MT 90. In the first part of the study, six normal volunteers participated. Viscosimetry was performed on native blood before and after heating the sample for 10 min at 50°C. Therefore, increasing concentrations of zinc gluconate (final concentration: 0.5–4 g/L) or isotonic NaCl as control medium were added to the sample. Heating induced a twofold increase in all indices of RBC rigidity (p<0.05). At all these concentrations of zinc, a highly significant, dose-related fluidifying effect was observed (40–70%): this effect was immediately obtained and did not change over 60 min. Even at the highest concentration, recovery was not complete. In the second part of the study, we studied magnesium’s effects on blood. In a first protocol, whole blood was rigidified by heating at 56°C for 10 min, and the correcting effect of 5 min of incubation at 37°C of RBCs in 150 mmol/L NaCl, MgSO₄, magnesium acetate, and magnesium gluconate was investigated. In a second protocol, the same incubation with NaCl and magnesium salts was made on blood that had not been previously heated. In a third protocol, the correcting effect of magnesium gluconate on heated red blood cells was tested at four concentrations (75, 150, 225, and 300 mmol/L) over 1 h, for evaluating the effects of both concentration and time. Erythrocyte rigidity by heating is corrected by the three salts employed in protocol 1 (compared to sodium). In protocol 2, the deformability of normal (nonheated) red cells is not modified by magnesium. In protocol 3, no marked modification over 1 h is observed. The correcting effect is not complete for 75 mmol/L Mg, but remains the same at the three other concentrations. This study shows that zinc and magnesium at supraphysiological concentration are able to reverse RBC’s rigidification induced by heating, but that magnesium does not modify the flexibility of normal RBCs. This article suggests that zinc and magnesium may be studied in vivo as potential pharmacologic tools for improving hemorheologic disturbances.