Cardiovascular Responses to Tonic Pain in REM Sleep-Deprived Rats: Role of Melatonin and Beta Endorphin.

OBJECTIVE: Chronic pain is associated with increased incidence of hypertension. Sleep deprivation, common in patients with chronic pain, is associated with increased blood pressure and heart rate. This study was designed to determine whether sleep deprivation induces increased cardiovascular responses to pain. In addition; we examined the role of melatonin and endorphins in mediating these responses. METHOD: The study was conducted in Sprague-Dawely rats divided into a control group (n=8) and Rapid Eye Moment sleep deprived (REMSD) group (n=8). REM sleep deprivation was done for three days using the inverted flowerpot technique. Systolic BP and HR were recorded at baseline as well as 5, 10 and 30 minutes after intra-plantar formalin injection. In addition, serum melatonin and endorphin levels were determined. RESULTS: Under basal conditions, BP and HR and following acute pain (1(st) phase of formalin injection) were comparable with non-sleep deprived (non-SD) state. In contrast, the REMSD rats showed significantly greater increases in HR and BP during the 2(nd) phase of formalin pain as compared to non-SD state. These changes were associated with significant reductions in serum melatonin and endorphin levels in REMSD rats. CONCLUSION: These data indicate that exaggerated blood pressure and HR responsiveness to pain in sleep deprivation could be mediated through reductions in melatonin and endorphin.

Student generated learning objectives: extent of congruence with faculty set objectives and factors influencing their generation.

CONTEXT: A problem-based learning strategy is used for curriculum planning and implementation at the Arabian Gulf University, Bahrain. Problems are constructed in a way that faculty-set objectives are expected to be identified by students during tutorials. Students in small groups, along with a tutor functioning as a facilitator, identify learning issues and define their learning objectives. PURPOSE: We compared objectives identified by student groups with faculty-set objectives to determine extent of congruence, and identified factors that influenced students' ability at identifying faculty-set objectives. METHOD: Male and female students were segregated and randomly grouped. A faculty tutor was allocated for each group. This study was based on 13 problems given to entry-level medical students. Pooled objectives of these problems were classified into four categories: structural, functional, clinical and psychosocial. Univariate analysis of variance was used for comparison, and a p > 0.05 was considered significant. RESULTS: The mean of overall objectives generated by the students was 54.2%, for each problem. Students identified psychosocial learning objectives more readily than structural ones. Female students identified more psychosocial objectives, whereas male students identified more of structural objectives. Tutor characteristics such as medical/non-medical background, and the years of teaching were correlated with categories of learning issues identified. CONCLUSION: Students identify part of the faculty-set learning objectives during tutorials with a faculty tutor acting as a facilitator. Students' gender influences types of learning issues identified. Content expertise of tutors does not influence identification of learning needs by students.

Regulation of acid secretion and paracellular permeability by F-actin in the bullfrog, Rana catesbeiana.

Many studies have implicated F-actin in the regulation of gastric acid secretion using cytochalasin D (CD) to disrupt apical actin filaments in oxyntic cells. However, it is known that CD also affects mucosal permeability by disrupting tight junction structure. Here we investigated the contribution of F-actin to mucosal permeability and acid secretion in the stomach using CD. Stomachs were mounted in Ussing chambers and acid secretion (stimulated or inhibited), transepithelial resistance (TER), mannitol flux, bicarbonate transport, and dual mannitol/sodium fluxes were determined with or without CD. H(+) back diffusion was predicted from its diffusion coefficient. Incubation with CD resulted in a significant reduction in stimulated acid secretion. TER was unchanged in stimulated tissues but significantly reduced in inhibited tissues. Mannitol flux, bicarbonate transport, and H(+)-back diffusion increased significantly with CD. However, the rates of bicarbonate and H(+) flux were not large enough to account for the inhibition of acid secretion. These findings demonstrate that actin filaments regulate paracellular permeability and play an essential role in the regulation of acid secretion in the stomach.