The above-ground coarse wood productivity of 104 Neotropical forest plots

The net primary production of tropical forests and its partitioning between long‐lived carbon pools (wood) and shorter‐lived pools (leaves, fine roots) are of considerable importance in the global carbon cycle. However, these terms have only been studied at a handful of field sites, and with no consistent calculation methodology. Here we calculate above‐ground coarse wood carbon productivity for 104 forest plots in lowland New World humid tropical forests, using a consistent calculation methodology that incorporates corrections for spatial variations in tree‐size distributions and wood density, and for census interval length. Mean wood density is found to be lower in more productive forests. We estimate that above‐ground coarse wood productivity varies by more than a factor of three (between 1.5 and 5.5 Mg C ha^?1 a^?1) across the Neotropical plots, with a mean value of 3.1 Mg C ha^?1 a^?1. There appear to be no obvious relationships between wood productivity and rainfall, dry season length or sunshine, but there is some hint of increased productivity at lower temperatures. There is, however, also strong evidence for a positive relationship between wood productivity and soil fertility. Fertile soils tend to become more common towards the Andes and at slightly higher than average elevations, so the apparent temperature/productivity relationship is probably not a direct one. Coarse wood productivity accounts for only a fraction of overall tropical forest net primary productivity, but the available data indicate that it is approximately proportional to total above‐ground productivity. We speculate that the large variation in wood productivity is unlikely to directly imply an equivalent variation in gross primary production. Instead a shifting balance in carbon allocation between respiration, wood carbon and fine root production seems the more likely explanation.     

Sleep assessment in a population-based study of chronic fatigue syndrome

Background

Chronic fatigue syndrome (CFS) is a disabling condition that affects approximately 800,000 adult Americans. The pathophysiology remains unknown and there are no diagnostic markers or characteristic physical signs or laboratory abnormalities. Most CFS patients complain of unrefreshing sleep and many of the postulated etiologies of CFS affect sleep. Conversely, many sleep disorders present similarly to CFS. Few studies characterizing sleep in unselected CFS subjects have been published and none have been performed in cases identified from population-based studies.

Methods

The study included 339 subjects (mean age 45.8 years, 77% female, 94.1% white) identified through telephone screen in a previously described population-based study of CFS in Wichita, Kansas. They completed questionnaires to assess fatigue and wellness and 2 self-administered sleep questionnaires. Scores for five of the six sleep factors (insomnia/hypersomnia, non-restorative sleep, excessive daytime somnolence, sleep apnea, and restlessness) in the Centre for Sleep and Chronobiology's Sleep Assessment Questionnaire^© (SAQ^©) were dichotomized based on threshold. The Epworth Sleepiness Scale score was used as a continuous variable.

Results

81.4% of subjects had an abnormality in at least one SAQ^© sleep factor. Subjects with sleep factor abnormalities had significantly lower wellness scores but statistically unchanged fatigue severity scores compared to those without SAQ^© abnormality. CFS subjects had significantly increased risk of abnormal scores in the non-restorative (adjusted odds ratio [OR] = 28.1; 95% confidence interval [CI]= 7.4–107.0) and restlessness (OR = 16.0; 95% CI = 4.2–61.6) SAQ^© factors compared to non-fatigued, but not for factors of sleep apnea or excessive daytime somnolence. This is consistent with studies finding that, while fatigued, CFS subjects are not sleepy. A strong correlation (0.78) of Epworth score was found only for the excessive daytime somnolence factor.

Conclusions

SAQ^© factors describe sleep abnormalities associated with CFS and provide more information than the Epworth score. Validation of these promising results will require formal polysomnographic sleep studies.

     

Genetic diversity of Costa Rican populations of the rice planthopper Tagosodes orizicolus (Homoptera: Delphacidae)

Tagosodes orizicolus (Homoptera: Delphacidae) is one of the main constraints of the rice production in the Neotropics. This planthopper produces severe damages as a phloem feeder, causes mechanical injury during oviposition and vectors the rice hoja blanca virus (RHBV). The main objective of this study was to determine the genetic diversity of T. orizicolus populations from three rice growing regions of Costa Rica, using RAPDs. Individuals from Guanacaste, Parrita, San Carlos and Cali-Colombia, as outgroup, were analyzed using the random primers. Phenetic relationships revealed that the Costa Rican populations were clearly separated from Cali-Colombia, sharing less than 25% similarity. Costa Rican populations were divided into two main branches separated at 30% similarity. The first branch included Guanacaste and San Carlos and the second displayed Parrita. In relation to similarity indexes within groups, the Guanacaste cluster showed the highest (over 50%) and Cali-Colombia was the most diverse (28%). The correspondence analysis confirmed the clusters of the phenogram and showed close interactions between the Parrita and San Carlos populations. The genetic separation observed could be the result of the geographic isolation among populations, but it could also be explained by the infection with the rickettsia Wolbachia pipientis. This bacterium causes cytoplasmic incompatibility in its host, which results in non-viable progeny when infected males mate with non-infected females, or when insects hosting different strains of Wolbachia mate. Then, a search for Wolbachia in previously described populations of T orizicolus was initiated. The presence of the bacteria was analyzed by PCR with 16S rDNA-specific primers for Wolbachia. The PCR analyses revealed infections of 86% in the population of San Carlos, 96% in Guanacaste, 37% in Parrita and 100% in Cali-Colombia. Crosses between individuals of T. orizicolus from Parrita and Guanacaste were performed for testing cytoplasmic incompatibility. When infected males were crossed with non-infected females within the same population, a significant reduction in progeny number was obtained as well as when crosses between infected individuals belonging to different populations were performed. These experiments showed cytoplasmic incompatibility not only caused by the presence of Wolbachia within the population, but also by the presence of different strains of the bacteria between populations.     

The effect of hexose ratios on metabolite production in Saccharomyces cerevisiae strains obtained from the spontaneous fermentation of mezcal

Mezcal from Tamaulipas (México) is produced by spontaneous alcoholic fermentation using Agave spp. musts, which are rich in fructose. In this study eight Saccharomyces cerevisiae isolates obtained at the final stage of fermentation from a traditional mezcal winery were analysed in three semi-synthetic media. Medium M1 had a sugar content of 100 g l^?1 and a glucose/fructose (G/F) of 9:1. Medium M2 had a sugar content of 100 g l^?1 and a G/F of 1:9. Medium M3 had a sugar content of 200 g l^?1 and a G/F of 1:1. In the three types of media tested, the highest ethanol yield was obtained from the glucophilic strain LCBG-3Y5, while strain LCBG-3Y8 was highly resistant to ethanol and the most fructophilic of the mezcal strains. Strain LCBG-3Y5 produced more glycerol (4.4 g l^?1) and acetic acid (1 g l^?1) in M2 than in M1 (1.7 and 0.5 g l^?1, respectively), and the ethanol yields were higher for all strains in M1 except for LCBG-3Y5, -3Y8 and the Fermichamp strain. In medium M3, only the Fermichamp strain was able to fully consume the 100 g of fructose l^?1 but left a residual 32 g of glucose l^?1. Regarding the hexose transporters, a high number of amino acid polymorphisms were found in the Hxt1p sequences. Strain LCBG-3Y8 exhibited eight unique amino acid changes, followed by the Fermichamp strain with three changes. In Hxt3p, we observed nine amino acid polymorphisms unique for the Fermichamp strain and five unique changes for the mezcal strains.     

A comparative genomic analysis of the small heat shock proteins in Caenorhabditis elegans and briggsae

The small heat shock proteins (sHSPs) are a ubiquitous family of molecular chaperones. We have identified 18 sHSPs in the Caenorhabditis elegans genome and 20 sHSPs in the Caenorhabditis briggsae genome. Analysis of phylogenetic relationships and evolutionary dynamics of the sHSPs in these two genomes reveals a very complex pattern of evolution. The sHSPs in C. elegans and C. briggsae do not display clear orthologous relationships with other invertebrate sHSPs. But many sHSPs in C. elegans have orthologs in C. briggsae. One group of sHSPs, the HSP16s, has a very unusual evolutionary history. Although there are a number of HSP16s in both the C. elegans and C. briggsae genomes, none of the HSP16s display orthologous relationships across these two species. The HSP16s have an unusual gene pair structure and a complex evolutionary history shaped by gene duplication, gene conversion, and purifying selection. We found no evidence of recent positive selection acting on any of the sHSPs in C. elegans or in C. briggsae. There is also no evidence of functional divergence within the pairs of orthologous C. elegans and C. briggsae sHSPs. However, the evolutionary patterns do suggest that functional divergence has occurred between the sHSPs in C. elegans and C. briggsae and the sHSPs in more distantly related invertebrates.     

Geography of underweight and overweight among women in India: A multilevel analysis of 3204 neighborhoods in 26 states

We investigated the geographic distribution and the relationship with neighborhood wealth of underweight and overweight in India. Using multilevel modeling techniques, we calculated state-specific smoothed shrunken state residuals of overweight and underweight, neighborhood and state variation of nutritional status, and the relationships between neighborhood wealth and nutritional status of 76,681 women living in 3204 neighborhoods in 26 Indian states. We found a substantial variation in overweight and underweight at the neighborhood and state levels, net of what could be attributed to individual-level factors. Neighborhood wealth was associated with increased levels of overweight and decreased levels of underweight, and was found to modify the relationship between personal living standard and nutritional status. These findings suggest that interventions to address the double burden of undernutrition and overnutrition in India must take into account state and neighborhood characteristics in order to be successful.     

Internal core protein cleavage leaves the hepatitis B virus capsid intact and enhances its capacity for surface display of heterologous whole chain proteins

Virus capsids find increasing use as nanoparticulate platforms for the surface display of heterologous ligands, including as multivalent vaccine carriers. Presentation on the icosahedral hepatitis B virus capsid (HBcAg) is known to strongly enhance immunogenicity of foreign sequences, most efficiently if they are inserted into the dominant c/e1 B cell epitope, a surface-exposed loop in the center of the constituent core protein primary sequence. Even some complete proteins were successfully inserted but others, e.g. the outer surface protein A (OspA) of the Lyme disease agent Borrelia burgdorferi, impaired formation of capsid-like particles (CLPs). This difference can be rationalized by the requirement for the termini of the insert to fit into the predetermined geometry of the two acceptor sites in the carrier. We reasoned that cleavage of one of the two bonds connecting insert and carrier should relieve these constraints, provided the cleaved protein fragments remain competent to support the particle structure. Indeed, HBcAg CLPs containing a recognition site for tobacco etch virus (TEV) protease in the c/e1 loop remained intact after cleavage, as did CLPs carrying a 65-residue peptide insertion. Most importantly, in situ cleavage of a core-OspA fusion protein by coexpressed TEV protease strongly enhanced CLP formation compared with the uncleaved protein. These data attest to the high structural stability of the HBcAg CLP and they significantly widen its applicability as a carrier for heterologous proteins. This approach should be adaptable to any protein-based particle with surface-exposed yet sequence-internal loops.