Aging and Human Hormonal and Pressor Responsiveness to Angiotensin II Infusion With Simultaneous Measurement of Exogenous and Endogenous Angiotensin II

A decline in the function of the renin angiotensin aldosterone system may induce adaptive changes in response to angiotensin II (ANG II) with age. We have examined platelet ANG II receptor density, blood pressure and aldosterone responses to ANG II [Asn1, Val5-ANG II] (Hypertensin, Ciba Geigy, Horsham, Sussex, England) infusion in 8 young, 24 to 30 years, and 8 older, 54 to 65 years, healthy volunteers. To measure circulating ANG II, we established a new method for specific and simultaneous measurement of exogenous [Asn1,Val5] (Hypertensin) and endogenous [Asp1,Ile5] ANG II in plasma by using isocratic HPLC and radioimmunoassays with cross-reacting antibodies and compared results with immunoreactive ANG II which was measured conventionally using monoclonal antibodies. Baseline endogenous ANG II (Asp1,Ile5-ANG II) levels in venous plasma were marginally, but not significantly, lower in the old [mean (95% confidence limits): 3.4 (< 0.1 to 7.7) ν 3.7 (1.2 to 6.2), fmol/ mL] and during suppression by the Hypertensin infusion appeared consistently, but not significantly, lower in the old [0.9 (0 to 3.1) ν 2.1 (0.6 to 3.7), after 3 ng/kg/min], while the same infusion rate in young and old resulted in similar plasma Hypertensin levels. Baseline systolic blood pressure (SBP) was similar in both groups but the percentage increases in SBP at infusion rates of 1, 3.0, and 10 ng/kg/min were greater in the old than in the young (9.1 ν 2.8, Ρ<.05; 16.3 ν 8.0, Ρ<.01; 30.4 ν 14.0%, Ρ<.001, respectively). The increment in diastolic blood pressure or mean arterial pressure during infusion did not differ significantly between the groups. Heart rate fell significantly during ANG II infusion in young (P < .05) but not old subjects. Basal plasma aldosterone was similar in both groups. However, the percentage increases in plasma aldosterone were greater in young than old at infusion rates of 1.0, 3.0, and 10.0 ng/kg/min (94 ν - 5 ; 238 ν 28; 462 ν 69%, all Ρ<.001). Platelet ANG II receptor density was elevated in the old [6.5 (1.9 to 11.1) ν 1.14 (0.21 to 2.07), fmol/109 cells, Ρ<.01]. Our findings demonstrate that it is possible to measure specifically and simultaneously exogenous and endogenous ANG II in plasma during Hypertensin infusion and that endogenous ANG II concentrations decrease with increasing levels of exogenous ANG II. During infusion, similar plasma Hypertensin levels were attained in both young and old, but systolic blood pressure responsiveness was increased in the old, while adrenal responsiveness was reduced. Am J Hypertens 1993;6:641-64

Effects of Aging and Hypertension on Plasma Angiotensin II and Platelet Angiotensin II Receptor Density

Plasma renin activity (PRA) declines with age in normal individuals, but the effect of age on plasma angiotensin II (ANG II) is less clear. A decline in plasma ANG II with age could result in altered platelet ANG II receptor density since plasma hormone levels influence their target organ receptors. To investigate this possibility, PRA, plasma ANG II, and platelet ANG II receptor density were examined in 17 young, 12 middle-aged, and 14 elderly healthy normotensive volunteers. To assess whether hypertension altered receptor density, these variables were also examined in 23 hypertensive patients. In normotensives, there was a negative correlation between age and PRA (r = — 0.43, P < .05), no significant change in basal plasma ANG II with age, and a weak positive correlation between age and ANG II receptor density (r = 0.34, P < .05). Multiple regression analysis revealed that the relationship between age and ANG II receptor density was independent of the associated rise in mean arterial arterial pressure with age (P < .05). Platelet ANG II receptor density was not significantly related to PRA or plasma ANG II. ANG II receptor affinity did not change with age. Neither PRA nor ANG II receptor density or affinity differed between hypertensives and normotensives of similar mean age, but plasma ANG II was significantly lower in hypertensives compared with normotensives. We concluded that aging is associated with a decline in supine PRA. The small decrease in plasma ANG II was not significant. Platelet ANG II receptor density increased with age primarily due to a small group of elderly subjects with elevated receptor density. There was no change in ANG II receptor density or affinity in hypertensives despite apparently lower plasma ANG II in these patients. Am J Hypertens 1992;5:687-69

Hypertext Theory and Narrative

The title of this essay may at first glance seem strange. The linkage of a computer based technology with a theory of narrative might seem incongruous; however, hypertext and what George Landow has called the \u27convergence of critical theory and technology\u27 has stimulated interest in new theories and problematics of the text and of narrative. Interest in studying the textual implications of hypertext systems has grown almost as rapidly as these systems themselves. It is not an overstatement to say that of all the technological developments of the twentieth century, the emergence of hypertext and the internet has been the most widely studied. The interdisciplinary nature of this work is perhaps its most notable feature and there is a need to see hypertext not merely as a technological phenomenon but as a system which has deep implications for many \u27communications· disciplines. There have been a few pioneers whose interdisciplinary work on hypertext predates the emergence of the World Wide Web (the most famous of hypertext systems) and whose work I will outline below

The origins of exercise adherence in the Canadian seniors population

This research identified and examined the responses of 19 physically active seniors to determine why they were physically active. The participants were physically active seniors, from the Niagara region who participated in physical activity 2, or more times per week. The purpose to this research was to determine what specific experiences or characteristics those seniors' possessed which motivated them to follow an exercise regime in later life. Three focus group interviews were conducted and participants responded to a set of predetermined questions. Responses to the interview questions were transcribed and analysed by comparing words and participant responses. This method of analysis is known as ethnographic summary. Themes, concepts, and experiences that emerged from the focus group interviews were also recorded according to systematic coding by way of content analysis. From this study, factors that predispose, enable, reinforce and prevent seniors from participating in exercise have been identified. Nine recommendations for improving seniors quality of life have also emerged from the study. Additionally, the findings from the study illustrate that those responsible for planning programs for seniors need to consider senior's wants and needs. Finally, the study also has educational implications. All participants in the study experienced a positive introduction to daily phyiscal activity through their school setting. Participants of the study believed, that their positive experiences at school, directly influenced their lifelong involvement in exercise

Recognition of micro-scale deformation structures in glacial sediments - pattern perception, observer bias and the influence of experience

It is a scientist's mission to try to remain unbiased. However, certain factors play a role in scientific analyses that are not controlled by conscious thought. These factors are potentially very important in areas of science where interpretations are based on a scientist's ability to identify patterns or structures. One such area is the micromorphology of glacial sediments. In this paper we investigate the role of an analyst's experience in relation to pattern perception with specific reference to turbate microstructures in glacial diamictons. An experiment was conducted on 52 participants, which demonstrated that, as may be expected, more experienced (glacial) micromorphologists tend to exhibit a higher sensitivity-to-signal, but that complete novices, if given clear instructions, can reach levels of sensitivity similar to those of experts. It also showed, perhaps more surprisingly, that response bias does not decrease with experience. We discuss psychological factors, such as the drive for success and consistency, that may have contributed to these results and investigate their possible implications in the micromorphological analysis and interpretation of glacial sediments

Storyscope: Supporting the authoring and reading of museum stories using online data sources

Museum staff tell stories to assist visitor interpretation of artworks. Visitors also tell their own stories to articulate their understanding and opinion of artworks. Additional knowledge about the concepts mentioned or tagged in these stories can be found from online data sources. These could be used to assist reader interpretation or author development of stories. However, the potentially vast network of heterogeneous knowledge that can be created around the tags or annotations of a story could be bewildering for the story reader or author. Here we present Storyscope, a test-bed environment for the authoring, reading and semantic annotation of museum stories. The integration of online knowledge within the task of story authoring or interpretation is facilitated by mapping the available knowledge to a set of facts and simple events related to each story annotation. Narrative principles of theme and setting are used to discover and highlight aspects of the knowledge of potential value to the author or reader. Preliminary studies indicate the potential of the approach for providing a form of semantic navigation across stories and concepts having a better cognitive fit to story related tasks than existing forms of navigation

Storyscope: Using setting and theme to assist the interpretation and development of museum stories

Stories are used to provide a context for museum objects, for example linking those objects to what they depict or the historical context in which they were created. Many explicit and implicit relationships exist between the people, places and things mentioned in a story and the museum objects with which they are associated. Storyscope is an environment for authoring museum stories comprising text, media elements and semantic annotations. A recommender component provides additional context as to how the story annotations are related directly or via other concepts not mentioned in the story. The approach involves generating a concept space for different types of story annotation such as artists and museum objects. The concept space of an annotation is predominantly made up of a set of events, forming an event space. The story context is aggregated from the concept spaces of its associated annotations. Narrative notions of setting and theme are used to reason over the concept space, identifying key concepts and time-location pairs, and their relationship to the rest of the story. The author or reader can use setting and theme to navigate the context of the story

Using event spaces, setting and theme to assist the interpretation and development of museum stories

Stories are used to provide a context for museum objects, for example linking those objects to what they depict or the historical context in which they were created. Many explicit and implicit relationships exist between the people, places and things mentioned in a story and the museum objects with which they are associated. We describe an interface for authoring stories about museum objects in which textual stories can be associated with semantic annotations and media elements. A recommender component provides additional context as to how the story annotations are related directly or via other concepts not mentioned in the story. The approach involves generating a concept space for different types of story annotation such as artists and museum objects. The concept space is predominantly made up of a set of events, forming an event space. The concept spaces of all story annotations can be combined into a single view. Narrative notions of setting and theme are used to reason over the concept space, identifying key concepts and time-location pairs, and their relationship to the rest of the story. Story setting and theme can then be used by the reader or author to assist in interpretation or further evolution of the story