Intranasal Immunization of Mice Against Naegleria fowleri1

ABSTRACT. The purpose of this research was to determine whether mice could be protected from lethal challenge with Naegleria fowleri by prior intranasal exposure to pathogenic and nonpathogenic Naegleria. Mortality ranged from 0 to 100% for mice inoculated intranasally (i.n.) with 5 × 10³ amebae of 13 human isolates of N. fowleri. Mice were immunized and challenged i.n. using live amebae of strains of low, medium, and high virulence. The greatest protection against lethal challenge was afforded by three immunizing doses of 10³ amebae per dose of the strain of medium virulence. Nonpathogenic N. gruberi also was used to immunize mice i.n. against lethal challenge with N. fowleri. Protection was greater following immunization with N. gruberi than it was after immunization with N. fowleri, suggesting that nonpathogenic N. gruberi may be a better immunogen in protecting mice against lethal naeglerial challenge.     

Phylogenetic relationships of the Papuan Swiftlet Aerodramus papuensis and implications for the evolution of avian echolocation

The swiftlets (genera Aerodramus , Collocalia and Hydrochous ) are unusual among birds in that many species can orientate in complete darkness using echolocation. The position of the Papuan Swiftlet Aerodramus papuensis in this group has been uncertain historically, in part due to morphological differences between it and other swiftlets (it has three toes instead of the usual four) and a lack of data on its behaviour (there is uncertainty about whether it echolocates). Here we investigate the phylogenetic affinities of the Papuan Swiftlet using DNA sequence data from two mitochondrial genes, cytochrome b and ND2. We present evidence that it is able to echolocate but, unlike previously studied species that use echolocation primarily while flying in caves, A. papuensis uses this ability while active outside caves at night. We also provide new evidence for placement of the monotypic Waterfall Swiftlet Hydrochous gigas , a species that does not echolocate. Our data provide strong support for a basal relationship between A. papuensis and other Aerodramus taxa and suggest that this species and H. gigas are sister taxa, a relationship that would indicate paraphyly of the genus Aerodramus . Our phylogeny provides new insights into how echolocation has evolved in the swiftlets, in particular by indicating higher levels of homoplasy in this trait than was previously thought.     

THE ULTRASTRUCTURE AND FUNCTION OF THE OESOPHAGUS OF PATELLA VULGATA LINNAEUS

The oesophagus of Patella vulgata Linnaeus is divisible intotwo histologically and functionally distinct regions, a centralfood channel and a series of lateral pouches forming the oesophagealglands: both are lined by a glandular ciliated columnar epithelium.Subepithelial mucous cells are restricted to the epitheliumlining the food channel and posterior section of oesophagus,whilst amylase-secreting cells occur only in the oesophagealglands. The activity of the ciliated cells lining the food channelmixes ingested food with saliva and mucus to form a food stringthat is carried towards the stomach. Amylase-secreting cellsproduce an extracellular amylase in the form of proteinaceoussecretory granules, which are released by apocrine secretionwithin cytoplasmic blebs. Release is correlated with periodsof immersion when feeding is possible. The free blebs are carriedout of the pouches and into the food channel where the amylaseinitiates carbohydrate digestion. The oesophageal epitheliumabsorbs tritiated D-glucose by a Na⁺-dependent mechanism inhibitedby 2,4-DNP and phloridzin and the amylase-secreting cells pinocytoseferritin. It is suggested that the oesophagus absorbs smallsolute molecules derived from ruptured algal cells and theirpartially digested polysaccharide storage products. There alsoappears to be pinocytosis of dissolved organic matter. ^*Current address: The R L. Weston Institute for NeurologicalStudiet, University College & Middlesex Medcal School, MortimerSt., London Wl. (Received 8 March 1988; accepted 29 April 1988)     

Nonlinear climate change and Andean feedbacks: an imminent turning point?

A 370 000‐year paleoecological record from Lake Titicaca provides a detailed record of past climate change in which interglacial periods are seen to have some elements of commonality, but also some key differences. We advance a conceptual feedback model to account for the observed changes that includes previously ignored lake effects. Today Lake Titicaca serves to warm the local environment by about 4–5 °C and also to increase rainfall. We observe that as water levels in the lake are drawn down due to warm, dry, interglacial conditions, there is a possible regional cooling as the lake effect on local microclimates diminishes. Positive feedback mechanisms promote drying until much of the lake basin is reduced to salt marsh. Consequently, the usual concept of upslope migration of species with warming would not be applicable in the Altiplano. If, as projected, the next century brings warmer and drier conditions than those of today, a tipping point appears to exist within ca. 1–2 °C of current temperatures, where the relatively benign agricultural conditions of the northern Altiplano would be replaced by inhospitable arid climates. Such a change would have profound implications for the citizens of the Bolivian capital, La Paz.