RESUMEN
Quantitative measurement of phlorotannins (polyphenolics) in brown algae (Phaeophyta) by colorimetric assays can be confounded because: (1) most such assays also react to nonphlorotannin substances (interferences) and (2) the appropriate reference compound for such assays is not always clear, although phloroglucinol is typically used. We developed a new assay in which 2,4-dimethoxybenzaldehyde (DMBA) reacts specifically with 1,3-and 1,3,5-substituted phenols (e.g., phlorotannins) to form a colored product. This new assay, as well as eliminating the problem of measuring interferences, is inexpensive, rapid, and can be used with small sample volumes. We recommend it for all assays of phlorotannins from one or a set of closely related species where the structural types of phlorotannins present are likely to be similar among samples. It is also appropriate for broader surveys of phlorotannin levels across many species, but in this case a reference must be chosen with care. We also compared the DMBA assay to existing assays, including the Folin-Denis [both before and after the samples were mixed with polyvinylpolypyrrolidone (PVPP)] and the Prussian blue assays. PVPP was not 100% efficient (and often much less) at removing phlorotannins from solution, and its effectiveness varied among different phlorotannins. Thus, in contrast to previous studies, measuring phenolic levels in extracts before and after treatment with PVPP will not necessarily result in an interference-free measure of phlorotannins. Based on an analysis of reactive substances in red and green algae (which do not contain phlorotannins) in the Folin-Denis and Prussian blue assays, we estimate that the average level of interferences (nonphlorotannins) in brown algae measured in these two assays is on the order of 0.5% by dry weight.
RESUMEN
Kelp forests are strongly influenced by macroinvertebrate grazing on fleshy macroalgae. In the North Pacific Ocean, sea otter predation on macroinvertebrates substantially reduces the intensity of herbivory on macroalgae. Temperate Australasia, in contrast, has no known predator of comparable influence. These ecological and biogeographic patterns led us to predict that (i) the intensity of herbivory should be greater in temperate Australasia than in the North Pacific Ocean; thus (ii) Australasian seaweeds have been under stronger selection to evolve chemical defenses and (iii) Australasian herbivores have been more strongly selected to tolerate these compounds. We tested these predictions first by measuring rates of algal tissue loss to herbivory at several locations in Australasian and North Pacific kelp forests. There were significant differences in grazing rates among sea otter-dominated locations in the North Pacific (0-2% day-1), Australasia (5-7% day-1), and a North Pacific location lacking sea otters (80% day-1). The expectations that chronically high rates of herbivory in Australasia have selected for high concentrations of defensive secondary metabolites (phlorotannins) in brown algae and increased tolerance of these defenses in the herbivores also were supported. Phlorotannin concentrations in kelps and fucoids from Australasia were, on average, 5-6 times higher than those in a comparable suite of North Pacific algae, confirming earlier findings. Furthermore, feeding rates of Australasian herbivores were largely unaffected by phlorotannins, regardless of the compounds' regional source. North Pacific herbivores, in contrast, were consistently deterred by phlorotannins from both Australasia and the North Pacific. These findings suggest that top-level consumers, acting through food chains of various lengths, can strongly influence the ecology and evolution of plantherbivore interactions.
RESUMEN
A 26-year-old woman underwent enucleation of a blind, painful eye because of a perforated corneal ulcer. Histopathologic examination of the eye disclosed an acute, necrotizing keratitis surrounding myriad small (2.5 to 3 x 4.5 to 5 micrometer), oval, faintly visible structures. Under polarized light, they were partially birefringent and stained intensely positive with the acid-fast technique. The organisms were located mainly within the cytoplasm of histiocytes in the deep corneal lamellae. They were interpreted as a protozoa of the genus Nosema. The diagnosis was confirmed by electron microscopic studies. The distinguishing features between Nosema species and Encephalitozoon are discussed. To our knowledge, this is the second documented case of corneal nosematosis.
Asunto(s)
Enfermedades de la Córnea/patología , Infecciones por Protozoos/patología , Adulto , Apicomplexa , Córnea/patología , Úlcera de la Córnea/etiología , Femenino , Humanos , Queratitis/etiología , Microscopía ElectrónicaRESUMEN
Flat preparations of the retina were prepared by trypsin digestion in ten cases of Coats' disease. All of the patients were young males with advanced disease leading to enucleation. All eyes showed marked abnormalities in the arterioles, venules, and capillaries. The findings most characteristic of Coats' disease were large aneurysms and thick PAS positive deposits in vessel walls. The aneurysms ranged from 50 to 350 microns and frequently formed large sausage-like or beaded out-pouchings and were sometimes situated on shunt vessels. Other findings frequently seen, but not specific for Coats' disease, were capillary dilatation, small aneurysms, hypocellular vessel walls, and fibrous strands.