Mating systems of two Bombacaceous trees of a neotropical moist forest.

A multilocus mixed mating model was used to analyze the mating systems of two tropical canopy trees in the Bombacaceae that differ in successional status and overall abundance. One population of each species was studied on Barro Colorado Island, Republic of Panama. Population outcrossing estimates of 0.57 and 0.35 from two years indicate a mixed-mating system with intermediate outcrossing levels for the gap-specialist Cavanillesia platanifolia, a relatively rare component of the island flora. Population and individual outcrossing estimates were associated with flowering tree density or degree of spatial isolation. Trees within clusters of flowering individuals have a higher degree of outcrossing than isolated trees. Annual estimates of individual tree outcrossing rates varied greatly as a function of flowering in its nearest neighbors. In contrast to C. platanifolia, Quararibea asterolepis was completely outcrossed and may be self incompatible. Maternal trees of both species had significantly heterogeneous pollen pools indicating non-random outcrossing. Apomixis by sporophytic agamospermy was rejected in C. platanifolia as contributing to the apparent selfing rate.

Pollen flow in Psiguria warscewiczii: a comparison of Heliconius butterflies and hummingbirds.

Pollen dispersal by male and female Heliconius butterflies and hermit hummingbirds was examined in a natural population of the tropical vine Psiguria warscewiczii. Fluorescent dyes were used to track flowers visited by individual pollinators. Mean distance of pollen dispersal was significantly higher by males than by female Heliconius. Butterflies dispersed pollen greater distances than did hummingbirds. There were no significant differences in dispersal distance among species of Heliconius. The number of flowers or plants to which dye was dispersed was greater for Heliconius than for hummingbirds.The home range behavior and site specificity exhibited by Heliconius, together with the preference by most Heliconius species in the study site for Psiguria led us to examine the relationship between the butterflies' home range and its daily foraging among Psiguria. A Heliconius mark-recapture program was conducted simultaneously with the dye program. This study showed that individual butterflies, for which extensive recaptures were made, visited an area of Psiguria plants on any one day that corresponded to the area in which those butterflies were caught or observed. The area over which a butterfly moved was termed its home range; within home ranges relative movement by butterflies was estimated as the mean distance between sequential captures. This estimate differed significantly among species of Heliconius; males of all species moving greater distances than females.

On the plasma protein binding of 16-acetyl-gitoxin.

The plasma protein binding of 16-acetyl-gitoxin (16-AG) was estimated in comparison with that of digoxin by the use of equilibrium dialysis, ultracentrifugation, and gel filtration techniques. Depending on temperature, the binding of 16-AG reached values between 81 and 90%. Calculations of the reaction enthalpy and entropy show that hydrophobic interaction results. The corresponding values of digoxin amount to 13 and 15%.

Pharmacokinetic investigations with 3H-penta-acetyl-gitoxin in volunteers and patients with respect to the occurrence of drug latentiation.

After oral administration of 3H-penta-acetyl-gitoxin (Pengitoxin W.H.O., Pentagit) 1.5 mg to four volunteers, serum radioactivity diclines with a half-life of 62 +/- 10 hours. After an oral maintenance dose of 0.4 mg pengitoxin in five digitalized patients, four of them with a cannulated bile duct, serum radioactivity declines with half-life of 56 +/- 8 hours. In volunteers within 4 days 50.7% of the administered radioactivity is excreted in urine; in the patients 52.3% in urine and 28.0% in bile. By thin-layer chromatographic studies, 16-acetyl-gitoxin was charactrized as the main metabolite in serum, bile and urine. Furthermore, in the first 8 hours after administration, two additional metabolites occur in urine.