In avian and mammalian embryos, surgical ablation or severely reduced migration of the cardiac neural crest leads to a failure of outflow tract septation known as persistent truncus arteriosus (PTA) and leads to embryo lethality due partly to impaired excitation-contraction coupling stemming primarily from a reduction in the L-type Ca(2+) current (I(Ca),(L)). Decreased I(Ca,L) occurs without a corresponding reduction in the alpha(1)-subunit of the Ca(2+) channel. We hypothesize that decreased I(Ca),(L) is due to reduced function at the single channel level. The cell-attached patch clamp with Na(+) as the charge carrier was used to examine single Ca(2+) channel activity in myocytes from normal hearts from sham-operated embryos and from hearts diagnosed with PTA at embryonic days (ED) 11 and 15 after laser ablation of the cardiac neural crest. In normal hearts, the number of single channel events per 200-ms depolarization and the mean open channel probability (P(o)) was 1.89 +/- 0.17 and 0.067 +/- 0.008 for ED11 and 1.14 +/- 0.17 and 0.044 +/- 0.005 for ED15, respectively. These values represent a normal reduction in channel function and I(Ca),(L) observed with development. However, the number of single channel events was significantly reduced in hearts with PTA at both ED11 and ED15 (71% and 47%, respectively) with a corresponding reduction in P(o) (75% and 43%). The open time frequency histograms were best fitted by single exponentials with similar decay constants (tau approximately or equal 4.5 ms) except for the sham operated at ED15 (tau = 3.4 ms). These results indicate that the cardiac neural crest influences the development of myocardial Ca(2+) channels.
The ability to provide constructive feedback is essential for physicians. The small group anatomy lab setting provides an ideal environment for assessing this skill. Medical students provide feedback via evaluative ratings & comments for lab partners & themselves at the end of each semester. We examined the quality & effectiveness of this feedback, hypothesizing that individuals would be more self‐critical, that ratings would increase over time & that students would identify more strengths than areas of improvement. Students rated themselves significantly lower than peers on all evaluative questions. Over the year, self‐ratings significantly increased in communication & self‐awareness categories, while peer ratings significantly increased in participation, preparedness & self‐awareness. Narrative comments placed more emphasis on strengths. When evaluating peers, 59% of positive comments were associated with professionalism, 21% with personal behaviors & 19% with knowledge. Similar results were seen in self‐reflections. Peer constructive criticism was more evenly distributed between professionalism (47%), personal behaviors (33%) & knowledge (20%). However, more students critiqued their own knowledge deficiencies (30%). Results indicate that students may be uncomfortable giving criticism & evaluate themselves more critically than their peers; yet, they do respond & improve with feedback.
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