Younger and older adults were tested for their ability to process and retrieve information from texts. The authors focused on the construction and retrieval of situation models relative to other types of text representations. The results showed that during memory retrieval, younger adults showed superior memory for surface form and textbase knowledge (what the text was), whereas older adults had equivalent or superior memory for situation model information (what the text was about). The results also showed that during reading, older and younger adults were similar in their sensitivity to various aspects of the texts. Overall, these findings suggest that although there are age-related declines in the processing and memory for text-based information, for higher level representations, these abilities appear to be preserved. Several possibilities for why this is the case are discussed, including an in-depth consideration of one possibility that involves W. Kintsch's (1988) construction-integration model.

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The ability of marine teleosts to actively excrete salts from the head region was first demonstrated by Smith (1930). Although cautious in his statement, he assumed the function to be localized in the gill structure. The perfusion experiments of Keys (1931), Bateman and Keys (1932) and Schlieper (1933) proved that the gill did indeed have that function.The identity of the cell responsible for the chloride transfer was first suggested by Keys and Willmer (1932). They gave no proof of its function, but made deductions to that end. Bevelander (1935 and1936), after a comparative survey of many fish gills, was inclined to the view that the general respiratory epithelium, rather than any special cells, was responsible.

Tungsten has been implicated as a cause of a severe form of pneumoconiosis in humans, the so-called "hard metal" lung disease. We have investigated the effect of intratracheal instillation of a powder of calcium tungstate on the pulmonary tissue of CD-1 mice. The tungsten-induced alterations were studied using 3 microanatomical methods: cytologic study of exudates obtained by bronchoalveolar lavage (BAL); histologic examination of paraffin-embedded sections of the lung; and scanning electron microscopic (SEM) examination of lung samples using x-ray microanalysis to detect tungsten in situ. The animals were sacrificed 1, 3, 7, 14 and 21 days after a single intratracheal instillation of 250 micrograms calcium tungstate particles suspended in 100 microliters of saline. We found that the metal particles induced a marked inflammatory response in the bronchoalveolar space characterized by a biphasic attraction of leukocytes with cellular peaks observed at day 1 and 14. More than 50% of the BAL macrophages showed ingested tungsten. In the lung parenchyma, the inflammatory infiltrates were predominantly located at the periphery of the bronchiolar walls. From 7 days on after the tungsten deposition, large inflammatory exudates were seen invading focal areas of the alveolar domain of the lung. SEM views revealed that the tungsten particles could be inside alveolar macrophages, in cells making up the alveolar wall, or inside periacinar lymphatics. Our data document that tungsten particles cause a marked inflammatory response in the lung tissue and that the leukocyte exudates may invade alveolar areas of the lung.(ABSTRACT TRUNCATED AT 250 WORDS)