Amazon tree dominance across forest strata

The forests of Amazonia are among the most biodiverse plant communities on Earth. Given the immediate threats posed by climate and land-use change, an improved understanding of how this extraordinary biodiversity is spatially organized is urgently required to develop effective conservation strategies. Most Amazonian tree species are extremely rare but a few are common across the region. Indeed, just 227 'hyperdominant' species account for >50% of all individuals >10 cm diameter at 1.3 m in height. Yet, the degree to which the phenomenon of hyperdominance is sensitive to tree size, the extent to which the composition of dominant species changes with size class and how evolutionary history constrains tree hyperdominance, all remain unknown. Here, we use a large floristic dataset to show that, while hyperdominance is a universal phenomenon across forest strata, different species dominate the forest understory, midstory and canopy. We further find that, although species belonging to a range of phylogenetically dispersed lineages have become hyperdominant in small size classes, hyperdominants in large size classes are restricted to a few lineages. Our results demonstrate that it is essential to consider all forest strata to understand regional patterns of dominance and composition in Amazonia. More generally, through the lens of 654 hyperdominant species, we outline a tractable pathway for understanding the functioning of half of Amazonian forests across vertical strata and geographical locations.

The presentation and management of multiple paraganglioma in head and neck

OBJECTIVE

We report the presentation and management of an 18-year-old male, who presented with bilateral carotid body paragangliomas and a unilateral jugular body paraganglioma.

METHOD

A comprehensive review of the medical literature concerning paragangliomas in the pediatric and adult population is discussed.

RESULTS

Presentations of multiple paragangliomas in an 18-year-old have never been described.

CONCLUSION

This is the first case of multiple paragangliomas in a 18-year-old male, who was treated with embolisation and surgical resection and remains disease free 2 years from surgery.

Effect of maternal hydration on mild fetal pyelectasis

The aim of our study was to determine whether maternal hydration status prior to prenatal sonography affects fetal renal pelvic diameter. The renal pelvic diameters of fetuses from two different institutions were compared prospectively. At one institution 74 women were asked to drink 32 to 48 ounces of water prior to undergoing sonography (hydration group), whereas at the second institution, no specific hydration regimen was requested of 176 subjects. The inclusion criteria were as follows: greater than 15 weeks' gestation, otherwise normal obstetrical sonogram, normal amniotic fluid volume, and negative family history for renal disease. Renal pelvic diameter, degree of maternal bladder fullness, and gestational age were compared between the two groups using logistic regression analysis and log-linear analysis. A P value < 0.01 was considered significant. Bladder fullness in the two groups differed significantly (P < 0.001). Logistic regression analysis showed a very strong effect of maternal bladder fullness on fetal renal pelvic diameter (P < 0.001). The log-linear analysis model showed a highly significant association between maternal bladder fullness and fetal renal pelvic diameter (P < 0.001). We conclude that maternal hydration influences fetal renal pelvic diameter. The larger fetal renal diameters seen in the hydrated group support physiologic theories that the effects of maternal hydration on amniotic fluid volume are partially mediated via fetal urine production.

Growth of tracheal anastomoses in lambs. Comparison of PDS and Vicryl suture material and interrupted and continuous techniques

Tracheal anastomoses were performed in 19 lambs (mean age 4 weeks, mean weight 9.8 kg) to compare polydioxanone (PDS) and polyglactin 910 (Vicryl) suture material (Ethicon, Inc., Somerville, N.J.) and simple continuous and simple interrupted suture technique. Each animal had two anastomoses with full-thickness bites for both suture techniques. Animals were killed at 4 months (n = 6) or 8 months (n = 5). Eight animals died before they were scheduled to be put to death (mean 6 weeks postoperatively). Transverse sections of the trachea were taken at the level of the anastomoses and three tracheal rings above and below each anastomosis. The cross-sectional area of the tracheal lumen of these transverse sections was measured with a computerized digitizing tablet. A percent luminal area for each anastomosis was calculated relative to the mean tracheal area three rings above and three rings below the anastomosis. There was little difference between interrupted and continuous technique with either suture material (p = 0.94). In 10 animals that each served as its own control for suture material, PDS anastomotic area was 55.0% +/- 4.1% of mean tracheal luminal area compared with 45.4% +/- 7.1% for Vicryl anastomoses (p = 0.06). Histologic analysis revealed a more intense inflammatory reaction surrounding multifilament Vicryl sutures with more rapid resorption and greater subsequent fibrosis relative to the reaction seen with PDS sutures. A small clinical experience with seven infants has confirmed short-term satisfactory clinical performance of continuous PDS suture for tracheal anastomosis.