Phenology of five tree species of a tropical dry forest in Yucatan, Mexico: effects of environmental and physiological factors

In order to relate phenological responses of trees to environmental variables we recorded the phenological patterns and select morphological and physiological traits (wood density and water potentials) of five tree species (Acacia gaumeri, Apoplanesia paniculata, Bursera simaruba, Gymnopodium floribundum, and Diospyros cuneata) in the tropical dry deciduous forest of the National Park of Dzibilchaltún, Yucatan, Mexico, over a period of 2 years (2004 and 2005). We chose two sites: one close to a permanent water source, locally known as ‘cenote’ (the CC site, ground water table was found at 2 m) and the other far from the cenote (FC site ground water table was at a depth of 10 m). Sites mainly differed in soil depth (FC site having greater soil depth) and soil nutrient characteristics (FC site more potassium, CC site more phosphorous). Our results indicated significant differences in phenology within species between sites and years, with leaf, flower and fruit production tending to be higher at the CC site and in the year 2004. Wood density and xylem water potentials were negatively related to each other, and midday water potentials were higher at the CC site. Differences in phenology found among years suggest that the timing of rainfall as well as the duration of periods without rain may play a more important role in phenology than total annual precipitation. Also differences inter-sites suggest a strong effect of site on tree phenology. Proximity to superficial bodies of water, such as cenotes, coupled with a greater concentration of available phosphorus in the soil may modify the effect of drought in this tropical dry deciduous forest.     

The role of β-ketoacyl-acyl carrier protein synthase III in the condensation steps of fatty acid biosynthesis in sunflower

The β-ketoacyl-acyl carrier protein synthase III (KAS III; EC 2.3.1.180) is a condensing enzyme catalyzing the initial step of fatty acid biosynthesis using acetyl-CoA as primer. To determine the mechanisms involved in the biosynthesis of fatty acids in sunflower (Helianthus annuus L.) developing seeds, a cDNA coding for HaKAS III (EF514400) was isolated, cloned and sequenced. Its protein sequence is as much as 72% identical to other KAS III-like ones such as those from Perilla frutescens, Jatropha curcas, Ricinus communis or Cuphea hookeriana. Phylogenetic study of the HaKAS III homologous proteins infers its origin from cyanobacterial ancestors. A genomic DNA gel blot analysis revealed that HaKAS III is a single copy gene. Expression levels of this gene, examined by Q-PCR, revealed higher levels in developing seeds storing oil than in leaves, stems, roots or seedling cotyledons. Heterologous expression of HaKAS III in Escherichia coli altered their fatty acid content and composition implying an interaction of HaKAS III with the bacterial FAS complex. Testing purified HaKAS III recombinant protein by adding to a reconstituted E. coli FAS system lacking condensation activity revealed a novel substrate specificity. In contrast to all hitherto characterized plant KAS IIIs, the activities of which are limited to the first cycles of intraplastidial fatty acid biosynthesis yielding C6 chains, HaKAS III participates in at least four cycles resulting in C10 chains.     

Sequencing of 6.7 Mb of the melon genome using a BAC pooling strategy

Background  

Cucumis melo (melon) belongs to the Cucurbitaceae family, whose economic importance among horticulture crops is second only to Solanaceae. Melon has a high intra-specific genetic variation, morphologic diversity and a small genome size (454 Mb), which make it suitable for a great variety of molecular and genetic studies. A number of genetic and genomic resources have already been developed, such as several genetic maps, BAC genomic libraries, a BAC-based physical map and EST collections. Sequence information would be invaluable to complete the picture of the melon genomic landscape, furthering our understanding of this species' evolution from its relatives and providing an important genetic tool. However, to this day there is little sequence data available, only a few melon genes and genomic regions are deposited in public databases. The development of massively parallel sequencing methods allows envisaging new strategies to obtain long fragments of genomic sequence at higher speed and lower cost than previous Sanger-based methods.     

<Emphasis Type="Italic">In planta</Emphasis> gene expression analysis of <Emphasis Type="Italic">Xanthomonas oryzae</Emphasis> pathovar <Emphasis Type="Italic">oryzae</Emphasis>, African strain MAI1

Background  

Bacterial leaf blight causes significant yield losses in rice crops throughout Asia and Africa. Although both the Asian and African strains of the pathogen, Xanthomonas oryzae pv. oryzae (Xoo), induce similar symptoms, they are nevertheless genetically different, with the African strains being more closely related to the Asian X. oryzae pv. oryzicola (Xoc).     

The Subjective Index for Physical and Social Outcome (SIPSO) in Stroke: investigation of its subscale structure

Background  

Short and valid measures of the impact of a stroke on integration are required in health and social settings. The Subjective Index of Physical and Social Outcome (SIPSO) is one such measure. However, there are questions whether scores can be summed into a total score or whether subscale scores should be calculated. This paper aims to provide clarity on the internal construct validity of the subscales and the total scale.     

Neurodegeneration in an Aβ-induced model of Alzheimer's disease: the role of Cdk5

Cdk5 dysregulation is a major event in the neurodegenerative process of Alzheimer's disease (AD). In vitro studies using differentiated neurons exposed to Aβ exhibit Cdk5-mediated tau hyperphosphorylation, cell cycle re-entry and neuronal loss. In this study we aimed to determine the role of Cdk5 in neuronal injury occurring in an AD mouse model obtained through the intracerebroventricular (icv) injection of the Aβ_1–40 synthetic peptide. In mice icv-injected with Aβ, Cdk5 activator p35 is cleaved by calpains, leading to p25 formation and Cdk5 overactivation. Subsequently, there was an increase in tau hyperphosphorylation, as well as decreased levels of synaptic markers. Cell cycle reactivation and a significant neuronal loss were also observed. These neurotoxic events in Aβ-injected mice were prevented by blocking calpain activation with MDL28170 , which was administered intraperitoneally (ip). As MDL prevents p35 cleavage and subsequent Cdk5 overactivation, it is likely that this kinase is involved in tau hyperphosphorylation, cell cycle re-entry, synaptic loss and neuronal death triggered by Aβ. Altogether, these data demonstrate that Cdk5 plays a pivotal role in tau phosphorylation, cell cycle induction, synaptotoxicity, and apoptotic death in postmitotic neurons exposed to Aβ peptides in vivo , acting as a link between diverse neurotoxic pathways of AD.     

Hormonal induction of spawning in 4 species of frogs by coinjection with a gonadotropin-releasing hormone agonist and a dopamine antagonist

Background  

It is well known that many anurans do not reproduce easily in captivity. Some methods are based on administration of mammalian hormones such as human chorionic gonadotropin, which are not effective in many frogs. There is a need for simple, cost-effective alternative techniques to induce spawning.     

A rational use of glucocorticoids in patients with early arthritis has a minimal impact on bone mass

Introduction  

Glucocorticoid (GC)-induced osteoporosis is a frequent complication in patients with rheumatoid arthritis. However, little information exists about the consequences of GC use in patients with early arthritis. Here we describe the variables underlying the use of GC in early arthritis, as well as its effect on bone-mineral density.     

3-Hydroxy-3-methylglutaryl-CoA reductase, mevalonate-5-pyrophosphate decarboxylase and acyl-CoA: cholesterol acyl-transferase from mucosa scrapings and isolated enterocytes from chick duodenum, jejunum and ileum

3-Hydroxy-3-methylglutaryl-CoA reductase, mevalonate-5-pyrophosphate decarboxylase and acyl-CoA: cholesterol acyltransferase activities were assayed in mucosal scrapings and isolated enterocytes from chick duodenum, jejunum and ileum. Maximal reductase and decarboxylase specific activities were found in ileum and jejunum, while ileum exhibited the minimal acyltransferase specific activity. The isolated epithelial cells showed levels of reductase and acyltransferase specific activities higher than those found in mucosa scrapings, probably due to the contact of these microsomal proteins with proteolytic enzymes during homogenization of the mucosa. However, no protecting effect of the trypsin inhibitor (2mg/ml) could be observed on reductase activity in mucosa scrapings. The cytosolic location of decarboxylase may account for the similar levels of specific activities found in mucosa scrapings and isolated enterocytes.