Myosin-Va mediates RNA distribution in primary fibroblasts from multiple organs

Myosin-Va has been shown to have multiple functions in a variety of cell types, including a role in RNA transport in neurons. Using primary cultures of cells from organs of young dilute-lethal (Myo5a(d-l)/Myo5a(d-l)) null mutant mice and wild-type controls, we show that in some, but not all, tissues, RNA distribution is dramatically different in the homozygous null mutant cells. The dependence of RNA localization on myosin-Va correlates with the relative abundance of the brain-specific splicing pattern of the myosin-Va tail. We also show that myosin-Va is involved in RNA localization soon after synthesis, because the effects of its absence are diminished for RNAs that are more than 30 min old. Finally, we show that localization of beta-actin mRNA is significantly changed by the absence of myosin-Va. These results suggest that myosin-Va is involved in a transient transport or tethering function in the perinuclear region.     

Pulsed electromagnetic fields induced femoral metaphyseal bone thickness changes in the rat

The effect of 1 Hz, 30 mT pulsed magnetic fields on young adult rat femoral metaphyseal bone thickness was assessed. Ten same litter, female Wistar rats were studied; five of them underwent 30 min magnetic stimulation sessions for 20 consecutive days. The anterior and posterior cortical, as well as trabecular bone transverse thicknesses were measured. The results obtained under clear field microscopy in stimulated and control histological cuts were (in microm) 398 +/- 32 versus 260 +/- 22 (P = 0.002), 380 +/- 68 versus 252 +/- 21 (P = 0.03), and 168 +/- 11 versus 112 +/- 11 (P = 0.002), respectively. The transcranial magnetic stimulation system, approved for human therapy, generates pulsed electromagnetic fields, which induce a significant thickness increase in cortical and trabecular in vivo stimulated bone tissues. This is the first time this effect in healthy animals is shown.     

SHORT COMMUNICATION: Do farmers reduce genetic diversity when they domesticate tropical trees? A case study from Amazonia

Agroforestry ecosystems may be an important resource for conservation and sustainable use of tropical trees, but little is known of the genetic diversity they contain. Inga edulis, a widespread indigenous fruit tree in South America, is used as a model to assess the maintenance of genetic diversity in five planted vs. five natural stands in the Peruvian Amazon. Analysis of five SSR (simple sequence repeat) loci indicated lower allelic variation in planted stands [mean corrected allelic richness 31.3 (planted) and 39.3 (natural), P = 0.009]. Concerns regarding genetic erosion in planted Amazonian tree stands appear valid, although allelic variation on-farm is still relatively high.     

Heterogeneity of NG2-expressing cells in the newborn mouse cerebellum

The function and origin of NG2+ cells in the adult brain are still controversial. A large amount of data is available which strongly indicates that adult NG2-expressing cells form a heterogeneous population, constituted by oligodendrocyte precursor cells (OPCs) and a fourth novel type of glial cells named the synantocytes. Whether these two populations derive from the progressive maturation of perinatal NG2+ OPCs or are generated as separate populations is not known. We used organotypic cultures of newborn mouse cerebellum depleted, by anti-mitotic drug treatment, of their NG2+ cells with perinatal features (high proliferating rate and high oligodendrocytic differentiation ability). In these cultures, despite the lack of myelin after 14 days in vitro, numerous NG2+ cells remained. We show that these BrdU-resistant cells were able to slowly divide, as adult NG2+ cells do. Although many of these cells expressed O4, only a very small fraction of them was further engaged in oligodendrocyte lineage, as they had an extremely poor capacity to generate myelin sheaths to the Purkinje cell axons. These results support the view that at least two distinct populations of NG2+ cells coexist in the cerebellum from birth: one with the young OPC characteristics, another with adult NG2+ cell characteristics. Thus, a fraction of adult NG2+ cells do not derive from the maturation of perinatal OPCs.     

Relationship between RNA synthesis and the Ca2+-filled state of the nuclear envelope store

RNA synthesis and ATP-dependent (45)Ca(2+) uptake were measured simultaneously in isolated nuclear fraction of rat liver nuclei. Maximal level of RNA synthesis was obtained under ATP-dependent (45)Ca(2+)-uptake conditions (1 microM free [Ca(2+)] and 1 mM ATP in the bathing solution). This experimental condition was defined as "stimulated nuclei" condition. ATP-dependent (45)Ca(2+) uptake was inhibited using different strategies including: (a) eliminating Ca(2+) (1 mM EGTA); (b) lowering the ATP concentration; (c) modifying nuclear envelope membranes Ca(2+) permeability (Ca(2+) ionophores); or (d) inhibiting the nuclear Ca(2+) pump (thapsigargin and 3',3',5',5'-tetraiodophenolsulfonephthalein). Under all the above conditions, RNA synthesis was lower than in "stimulated nuclei" condition. In the presence of ionomycin, RNA synthesis was significantly higher at 500 nM free [Ca(2+)], as compared with RNA synthesis in a Ca(2+)-free medium or at 1muM free [Ca(2+)]. However, even in such condition (500 nM free [Ca(2+)]), RNA synthesis was lower than RNA synthesis obtained in "stimulated nuclei" condition. We suggest two components for the effect of Ca(2+) on RNA synthesis: (A) a direct effect of nucleoplasmic [Ca(2+)]; and (B) an effect dependent on the accumulation of Ca(2+) in the nuclear envelope store mediated by the SERCA nuclear Ca(2+) pump.     

Calcium efflux from platelet vesicles of the dense tubular system. Analysis of the possible contribution of the Ca2+ pump

The ATP dependent Ca²⁺ uptake of platelet vesicles was inhibited by the two hydrophobic drugs trifluoperazine (TFP) and propranolol (PROP). Inhibition was significantly lowered when Pi was used instead of oxalate as a precipitant agent. When the ATPase ligands substrate (Mg²⁺ and Pi) were absent of the efflux medium, a slow release of Ca²⁺ which did not couple with ATP synthesis (passive Ca²⁺ efflux) was observed. Both, TFP and PROP enhanced the passive Ca²⁺ efflux. This enhanced efflux was partially inhibited only when Mg²⁺ and Pi were added together to the efflux reaction media, but it was not affected by spermidine, ruthenium red or thapsigargin (TG). The Ca²⁺ ionophores A23187 and ionomycin, also enhanced passive Ca²⁺ efflux. However, in this case, Ca²⁺ efflux was inhibited just by inclusion of Mg²⁺ to the medium. Ca²⁺ efflux promoted by Triton X-100 was not affected by either Mg²⁺ or Pi, included together or separately into the efflux medium. The ATP Pi measured in the presence of Triton X-100 and millimolar Ca²⁺ concentrations was inhibited by both TFP and PROP, but not by Ca²⁺ ionophores up to 4 M. The data suggest that the observed enhancement of passive Ca²⁺ efflux promoted by TFP and PROP could be attributed to a direct effect of these drugs over the platelet Ca²⁺ pump isoforms (Sarco Endoplasmic Reticulum Calcium ATPase, SERCA_2b and SERCA₃) themselves, as it was reported for the sarcoplasmic reticulum Ca²⁺ ATPase (SERCA₁).     

Origins of food crops connect countries worldwide

Research into the origins of food plants has led to the recognition that specific geographical regions around the world have been of particular importance to the development of agricultural crops. Yet the relative contributions of these different regions in the context of current food systems have not been quantified. Here we determine the origins (‘primary regions of diversity’) of the crops comprising the food supplies and agricultural production of countries worldwide. We estimate the degree to which countries use crops from regions of diversity other than their own (‘foreign crops’), and quantify changes in this usage over the past 50 years. Countries are highly interconnected with regard to primary regions of diversity of the crops they cultivate and/or consume. Foreign crops are extensively used in food supplies (68.7% of national food supplies as a global mean are derived from foreign crops) and production systems (69.3% of crops grown are foreign). Foreign crop usage has increased significantly over the past 50 years, including in countries with high indigenous crop diversity. The results provide a novel perspective on the ongoing globalization of food systems worldwide, and bolster evidence for the importance of international collaboration on genetic resource conservation and exchange.     

Serial sectioning study of some meiotic stages in Scaptericus borrelli (Grylloidea)

An electron microscope study of the spermatocytes I of Scaptericus borrelli was performed using serial sections and tridimensional reconstruction. The stages examined were: mid-pachytene, early diplotene and the so-called diffuse stage. At mid-pachytene the nucleolus (associated to an autosome) shows a glomerular array formed of supernumerary synaptonemal complexes (extra-complexes, ECs). At early diplotene the autosomes still show remnants of synaptonemal complexes (SC) and the sex chromosome is formed by two substances: one is homogeneous (chromatin-like) the other is granular and dense. A short number of ECs occur in the latter. — At the diffuse stage (lobulated in this paper) the SCs remnants and the ECs have disappeared and the granular material is assembled in a nuclear lobule. This lobule was found associated with one centriole. — A tridimensional model of a diplotene nucleus and models of diplotene bivalents are shown. — The capacity to form repetitive components of the synaptonemal complex type by spermatocytes of the super-Family Grylloidea is discussed.     

Ventricular injection of nerve growth factor increases dopamine content in the striata of MPTP-treated mice

Experimental depletion of dopaminergic striatal neurons was induced in mice with the neurotoxin MPTP. To investigate a possible effect of nerve growth factor on the damaged neurons, we injected 4 g into the right cerebral ventricle of mice three days after the last administration of MPTP. We found a significant increase of dopamine and homovanillic acid in the striatum of MPTP treated mice after NGF administration when compared with dopamine and HVA levels in MPTP-treated control mice (p<0.001). The increase of dopamine and homovanillic acid seems to be related to a partial restorative effect of NGF on the damaged dopaminergic cells, since ventricular administration of NGF to normal mice did not increase dopamine or homovanillic acid contents above the levels measured in untreated controls. It appears that administration of nerve growth factor prcduces a beneficial effect on damaged dopaminergic neurons; this effect could be due to stimulation of neuron sprouting from neurons that survived the toxic effect of MPTP. The increase of dopamine levels was seen 8 days after injection of nerve growth factor and was maintained at least until day 25, showing a lasting persistence of the restorative effect.