Spatial patterns of sapling mortality in a moist tropical forest: consistency with total density‐dependent effects

Density‐dependent mortality (DDM) is major driver of species coexistence in tropical forests. We assessed the occurrence and strength of this mechanism among saplings (i.e. trees with a diameter of 1–4 cm) in the moist tropical forest of Barro Colorado Island (BCI), Panama, over six inter‐census periods (26 years), by using spatial point pattern analysis. We considered conspecific density‐dependent mortality, but also total DDM (i.e. the effects of conspecific and heterospecific neighbours all together) upon saplings of all species (i.e. at the community level), and on saplings of light‐demanding and shade‐tolerant ones, separately (i.e. at the light‐guild level). We also analysed the effects of conspecific DDM at the community and light‐guild levels. Conspecific density‐dependent mortality affected a lower proportion of species than was to be expected. Its strength was not significantly related with species abundance, and it had relatively weak effects at the community and light guild levels. Conversely, we detected a significant spatial signature of total DDM among all saplings, and among saplings of the light‐demanding and shade‐tolerant species, but its strength showed pronounced temporal variation. Total DDM among light‐demanding saplings was stronger than among shade‐tolerant ones and its effects were particularly marked 10–15 years after the occurrence of unusually severe droughts associated with El Niño events. Our study indicates that conspecific DDM is relatively unimportant among saplings in comparison with total DDM at community and light‐guild levels. This finding contrasts strongly with the results for seedlings, where conspecific DDM was constituted the dominant process. The pronounced temporal variations observed in the occurrence and strength of total DDM among saplings indicate that time‐varying events associated with climatic disturbances such as canopy openings or episodes of high recruit emergence might be important drivers of this process. They also emphasize the importance of considering time frames longer than one decade to study density‐dependent effects among saplings in tropical forests.     

Spatial patterns of an endemic Mediterranean palm recolonizing old fields

Throughout Europe, increased levels of land abandonment lead to (re)colonization of old lands by forests and shrublands. Very little is known about the spatial pattern of plants recolonizing such old fields. We mapped in two 21–22‐ha plots, located in the Doñana National Park (Spain), all adult individuals of the endozoochorous dwarf palm Chamaerops humilis L . and determined their sex and sizes. We used techniques of spatial point pattern analysis (SPPA) to precisely quantify the spatial structure of these C. humilis populations. The objective was to identify potential processes generating the patterns and their likely consequences on palm reproductive success. We used (1) Thomas point process models to describe the clustering of the populations, (2) random labeling to test the sexual spatial segregation, and (3) mark correlation functions to assess spatial structure in plant sizes. Plants in both plots showed two critical scales of clustering, with small clusters of a radius of 2.8–4 m nested within large clusters with 38–44 m radius. Additional to the clustered individuals, 11% and 27% of all C. humilis individuals belonged to a random pattern that was independently superimposed to the clustered pattern. The complex spatial pattern of C. humilis could be explained by the effect of different seed‐dispersers and predators' behavior and their relative abundances. Plant sexes had no spatial segregation. Plant sizes showed a spatial aggregation inside the clusters, with a decreasing correlation with distance. Clustering of C. humilis is strongly reliant on its seed dispersers and stressful environmental conditions. However, it seems that the spatial patterns and dispersal strategies of the dwarf palm make it a successful plant for new habitat colonization. Our results provide new information on the colonization ability of C. humilis and can help to develop management strategies to recover plant populations.     

Evaluating the Burden of Lymphedema Due to Lymphatic Filariasis in 2005 in Khurda District,Odisha State,India

BackgroundOver 1.1 billion people worldwide are at risk for lymphatic filariasis (LF), and the global burden of LF-associated lymphedema is estimated at 16 million affected people, yet country-specific estimates are poor.SignificanceThese data highlight the magnitude of lymphedema in LF-endemic areas and emphasize the need to develop robust estimates of numbers of individuals with lymphedema in order to identify the extent of lymphedema management services needed in these regions.     

Collapsibility of the human upper airway during normal sleep

Upper airway resistance (UAR) increases in normal subjects during the transition from wakefulness to sleep. To examine the influence of sleep on upper airway collapsibility, inspiratory UAR (epiglottis to nares) and genioglossus electromyogram (EMG) were measured in six healthy men before and during inspiratory resistive loading. UAR increased significantly (P less than 0.05) from wakefulness to non-rapid-eye-movement (NREM) sleep [3.1 +/- 0.4 to 11.7 +/- 3.5 (SE) cmH2O.1-1.s]. Resistive load application during wakefulness produced small increments in UAR. However, during NREM sleep, UAR increased dramatically with loading in four subjects although two subjects demonstrated little change. This increment in UAR from wakefulness to sleep correlated closely with the rise in UAR during loading while asleep (e.g., load 12: r = 0.90, P less than 0.05), indicating consistent upper airway behavior during sleep. On the other hand, no measurement of upper airway behavior during wakefulness was predictive of events during sleep. Although the influence of sleep on the EMG was difficult to assess, peak inspiratory genioglossus EMG clearly increased (P less than 0.05) after load application during NREM sleep. Finally, minute ventilation fell significantly from wakefulness values during NREM sleep, with the largest decrement in sleeping minute ventilation occurring in those subjects having the greatest awake-to-sleep increment in UAR (r = -0.88, P less than 0.05). We conclude that there is marked variability among normal men in upper airway collapsibility during sleep.     

Chemiluminescent labels for steroid immunoassays

During the last few years non-isotopic techniques have been developed to measure steroid hormones. One of these methods is the luminescence immunoassay. Three classes of substances have been found to yield reasonable results, i.e. aminophthalhydrazides, aminonaphthohydrazides and acridiniumesters. Examples of application are shown.     

Inducer and culture medium dependent properties of extracellular laccase from Botrytis cinerea

Both the composition of the culture medium and the nature of the phenolic inducer determine the amount, the rate of formation and the molecular properties of extracellular laccase formed by Botrytis cinerea. Coumaric acid is shown to act as inducer in addition to gallic acid and grape juice. It is suggested that the fungus adapts to different environments by excreting different laccases. These laccases differ in pK, heat stability and substrate specificity but not in K_m values to quinol and oxygen.     

Effect of geniohyoid and sternohyoid muscle contraction on upper airway resistance in the cat.

Previous investigators (van Lunteren et al. J. Appl. Physiol. 62: 582-590, 1987) have suggested that the geniohyoid and sternohyoid muscles may act as upper airway dilators in the cat. To investigate the effect of geniohyoid and sternohyoid contraction on inspiratory upper airway resistance (UAR), we studied five adult male cats anesthetized with ketamine and xylazine during spontaneous room-air breathing. Inspiratory nasal airflow was measured by sealing the lips and constructing a nose mask. Supraglottic pressure was measured using a transpharyngeal catheter placed above the larynx. Mask pressure was measured using a separate catheter. Geniohyoid and sternohyoid lengths were determined by sonomicrometry. Geniohyoid and sternohyoid contraction was stimulated by direct muscle electrical stimulation with implanted wire electrodes. Mean inspiratory UAR was determined for spontaneous breaths under three conditions: 1) baseline (no muscle stimulation), 2) geniohyoid contraction alone, and 3) sternohyoid contraction alone. Geniohyoid contraction alone produced no significant reduction in inspiratory UAR [unstimulated, 17.75 +/- 0.86 (SE) cmH2O.l-1.s; geniohyoid contraction, 19.24 +/- 1.10]. Sternohyoid contraction alone also produced no significant reduction in inspiratory UAR (unstimulated, 15.74 +/- 0.92 cmH2O.l-1.s; sternohyoid contraction, 14.78 +/- 0.78). Simultaneous contraction of the geniohyoid and sternohyoid muscles over a wide range of muscle lengths produced no consistent change in inspiratory UAR. The geniohyoid and sternohyoid muscles do not appear to function consistently as upper airway dilator muscles when UAR is used as an index of upper airway patency in the cat.