Two experiments assessed effects of activation of prior knowledge through small-group discussion. Subjects were given a description of natural phenomena and were asked to elaborate on possible explanations for them. In Experiment 1, small groups of subjects were presented with a problem describing the behavior of a blood cell in pure water and in a salt solution. No additional text was studied. The experimental subjects produced more than twice as many propositions about osmosis (i.e. the biological process explaining the blood cell's behavior) as a control group produced. Experiment 2 investigated effects of problem analysis on subsequent text processing for subjects with imprecise prior knowledge (novices) and subjects with precise knowledge (experts). Recall of the text showed considerable facilitative effects of problem analysis. Results are explained in terms of faster accessibility of prior knowledge and better integration of new information into explanatory models that may exist before, or are actively constructed during, problem analysis.
An important phase of problem-based learning in a tutorial group is problem analysis. This article describes a study investigating the ongoing cognitive and metacognitive processes during problem analysis, by analysing the verbal communication among group members, and their thinking processes. Thinking processes were tapped by means of a stimulated recall procedure. Verbatim transcripts of both the verbal interaction in the group and the recall protocols were analysed. The goal of this research is two-fold, i.e., to investigate whether PBL indeed leads to conceptual change and to develop a method that is sensitive to these phenomena.The results suggest that the verbal interaction in a group shows only the tip of the iceberg of the cognitive and metacognitive processes on which it is based. The verbal interaction in the small group discussion mainly concerned theory building, and to a lesser extent, data exploration and meta-reasoning. Stimulated recall of the thinking process during that discusion, however, provides more and unique information about hypothesis evaluation and meta-reasoning. In the protocols of stimulated recall, the process of conceptual change by students could be made visible. The ways of dealing with anomalous data could be described as well as the conditions that determine how students deal with anomalous data. These results suggest that the method was sensitive for detecting conceptual change during problem analysis.
Thrombotic microangiopathy (TMA) is a pattern of endothelial damage that can be found in association with diverse clinical conditions such as malignant hypertension. Although the pathophysiological mechanisms differ, accumulating evidence links complement dysregulation to various TMA syndromes and in particular the atypical hemolytic uremic syndrome. Here, we evaluated the role of complement in nine consecutive patients with biopsy-proven renal TMA attributed to severe hypertension. Profound hematologic symptoms of TMA were uncommon. In six out of nine patients, we found mutations C3 in three, CFI in one, CD46 in one, and/or CFH in two patients either with or without the risk CFH-H3 haplotype in four patients. Elevated levels of the soluble C5b-9 and renal deposits of C3c and C5b-9 along the vasculature and/or glomerular capillary wall, confirmed complement activation in vivo. In contrast to patients without genetic defects, patients with complement defects invariably progressed to end-stage renal disease, and disease recurrence after kidney transplantation seems common. Thus, a subset of patients with hypertension-associated TMA falls within the spectrum of complement-mediated TMA, the prognosis of which is poor. Hence, testing for genetic complement abnormalities is warranted in patients with severe hypertension and TMA on renal biopsy to adopt suitable treatment options and prophylactic measures.
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