No abstract

In general, cardiac regulation is dominated by the sympathetic and parasympathetic nervous systems in men and women, respectively. Our recent study had revealed sex differences in the forebrain network associated with sympathoexcitatory response to baroreceptor unloading. The present study further examined the sex differences in forebrain modulation of cardiovagal response at the onset of isometric exercise. Forebrain activity in healthy men (n = 8) and women (n = 9) was measured using functional magnetic resonance imaging during 5 and 35% maximal voluntary contraction handgrip exercise. Heart rate (HR), mean arterial pressure (MAP), and muscle sympathetic nerve activity (MSNA) were collected in a separate recording session. During the exercise, HR and MAP increased progressively, while MSNA was suppressed (P < 0.05). Relative to men, women demonstrated smaller HR (8 +/- 2 vs. 18 +/- 3 beats/min) and MAP (3 +/- 2 vs. 11 +/- 2 mmHg) responses to the 35% maximal voluntary contraction trials (P < 0.05). Although a similar forebrain network was activated in both groups, the smaller cardiovascular response in women was reflected in a weaker insular cortex activation. Nevertheless, men did not show a stronger deactivation at the ventral medial prefrontal cortex, which has been associated with modulating cardiovagal activity. In contrast, the smaller cardiovascular response in women related to their stronger suppression of the dorsal anterior cingulate cortex activity, which has been associated with sympathetic control of the heart. Our findings revealed sex differences in both the physiological and forebrain responses to isometric exercise.

No abstract

3128 Poster Board III-65 Enoxaparin (Lovenox®), fondaparinux (Arixtra®) and rivaroxaban (Xarelto®) have been shown to be effective in mediating antithrombotic effects in post-surgical indications. Because of marked differences in the pharmacokinetic and pharmacodynamic behavior of these drugs we hypothesized that after the last dosage, the duration of the residual antithrombotic activity of the various drugs also differs. In order to compare the duration of effect of these three drugs, a rabbit stasis-thrombosis model (RSTM) utilizing FEIBA as the thrombogenic challenge and a rabbit ear bleeding model (REBM) were employed. Individual groups of rabbits (n=5) were treated with doses to mimic prophylactic, therapeutic and supratherapeutic (5x therapeutic) drug levels. Enoxaparin and fondaparinux were administered subcutaneously and rivaroxaban was administered by oral gavage. Blood samples were collected at baseline and at 16-18 hours post-administration of the last dose on day 1 or after 4 days of repeated dosing in the RSTM or at 3 hours post-administration in the REBM. At the 16-18 hour time point, circulating anti-Xa levels were not observed in any of the treatment groups. Despite this, enoxaparin treated animals exhibited a strong antithrombotic response following administration of the therapeutic dose (clot score = 1.3 ± 0.6 vs. 2.7 ± 0.6 for saline controls). Dosing once daily for four days did not enhance the antithrombotic activity of enoxaparin. In the plasmatic thrombin generation assays, a reduction in thrombin generation was noted in samples from enoxaparin-treated animals. For enoxaparin, no increase in bleeding was observed at prophylactic or therapeutic doses when compared to saline. An increase in bleeding (∼5 fold vs. saline) was observed at 3 and 6 hours post-administration of the ‘overdose’. A dose-dependent increase in anti-Xa activity was observed in blood samples collected 3 hours post-administration. For fondaparinux, no increase in bleeding was observed with any of the doses tested. There was a moderate increase in anti-Xa activity in the samples from rabbits treated with the ‘overdose’ of fondaparinux. This level was comparable to that observed with the therapeutic dose of enoxaparin. These studies suggest that enoxaparin produces a sustained antithrombotic effect in contrast to rivaroxaban and fondaparinux. These observations underscore that residual/sustained antithrombotic effects of enoxaparin may be partly responsible for the prolonged antithrombotic actions associated with the clinical use of enoxaparin. Disclosures No relevant conflicts of interest to declare.

Rationale and objectivesWe sought to incorporate a new teaching module into the traditional medical student radiology clerkship, to improve the necessary skills for future referring physicians.Materials and methodsA new required and graded module was introduced in 2014 into the radiology clerkship in year three of medical school: the Mystery Case. Each student was provided a unique and undifferentiated case from a dedicated teaching file containing de-identified images and requisition data. Students were expected to complete three serial tasks over one week: 1) prepare a voice recognition-derived, structured radiological report utilizing appropriate and relevant vocabulary; 2) discuss pertinent additional clinical information; and 3) discuss appropriate follow-up imaging, in addition to information on how to best prepare patients for these potential patient exams (e.g., with or without contrast, bowel preparation, and length of study). Students were provided written examples and dedicated class instruction with interactive discussions covering specific cases and associated related cases through random pairing with radiology resident and attending mentors. At the close of the week, students gave brief oral presentations of their cases and submitted the tasks for a written evaluation. Upon completion of the clerkship, the students completed a Likert-type six-item survey to evaluate the perceived improvement in select skills.ResultsThe survey was completed by 82% (54/66) of the enrolled students, with 85% finding the Mystery Case an effective use of time. Medical students perceived an improved awareness of the patient care process (77%), awareness of the medical imaging resources available (89%), ability to understand a radiology report (74%), and ability to advise patients (69%).ConclusionIntroduction of the Mystery Case as a graded exercise in the medical school radiology clerkship was perceived by students as effective use of time, with an improvement in the skills essential for future referring physicians.