Suitability of the pericardiophrenic veins for phrenic nerve stimulation: an anatomic study.

OBJECTIVE: The objective of this study was to assess the potential of the pericardiophrenic veins (PPVs) as conduits for transvenous stimulation of the phrenic nerves. Modulating respiration with transvenous phrenic nerve stimulation via the PPVs might reduce or eliminate the adverse effects of central sleep apnea in heart failure. METHODS: Forty-eight fixed cadavers were dissected to study the anatomic characteristics of the PPVs and related neurovascular structures. RESULTS: The right PPV, found in only 1 of 35 cadavers, was <0.5 mm diameter. The left PPV, located in all 48 cadavers, drained into the left brachiocephalic vein (BCV) directly or into the BCV via the superior intercostal vein (SICV). Mean ± SD SICV trunk diameter was 4 ± 2 mm. Mean ± SD left PPV diameter was 2 ± 1 mm. The length between the point of separation of the left PPV from the phrenic nerve to its junction with the BCV or SICV trunk ranged from 6 to 40 mm. The angle of approach, defined as the angle formed by the intersection of the longitudinal axis of the BCV and the longitudinal axis of the PPV or SICV trunk, and which represents the angle that would need to be navigated when inserting a stimulation lead into the PPV using a peripheral cannulation approach, was 99 ± 28 degrees. Valves were identified in 54% of left PPVs. CONCLUSIONS: Because of its extremely small size, the right PPV appears unsuitable for transvenous phrenic nerve stimulation. In contrast, the left PPV may be accessible via the left BCV using standard transvenous catheterization techniques; however, the small caliber of the left PPV and the frequent presence of valves within it might pose challenges in navigating the vessel to achieve transvenous phrenic nerve stimulation.

The Minnesota pelvic trainer: a hybrid VR/physical pelvis for providing virtual mentorship.

Obtaining accurate understanding of three dimensional structures and their relationships is important in learning human anatomy. To leverage the learning advantages of using both physical and virtual models, we built a hybrid platform consisting of virtual and mannequin pelvis, motion tracking interface, anatomy and pathology knowledge base. The virtual mentorship concept is to allow learners to conveniently manipulate and explore the virtual pelvic structures through the mannequin model and VR interface, and practice on anatomy identification tasks and pathology quizzes more intuitively and interactively than in a traditional self-study classroom, and to reduce the demands of access to dissection lab or wet lab.

An Interprofessional Senior Medical Student Preparation Course: Improvement in Knowledge and Self-Confidence Before Entering Surgical Training.

PURPOSE: Senior medical students are variably prepared to begin surgical training; and a national curriculum was established through the American College of Surgeons to better prepare senior medical students for surgical training. The purpose of our course is to prepare senior medical students to more effectively enter surgical training programs. We recently enhanced our independently developed surgical training preparation course by increasing exposure to surgical anatomy, medical physiology, surgical skills, and point-of-care ultrasound. We evaluated the impact of our interprofessional training course to increase confidence and readiness among senior medical students entering surgical training. METHODS: The course focused on pre- and post-operative patient care, surgical anatomy, human physiology, and bedside ultrasound. Didactic lectures in anatomy, human physiology, and bedside ultrasound were provided prior to all hands-on simulated patient care sessions and mock surgical procedures. To evaluate our interprofessional curriculum, we administered pre- and post-course surveys, pre- and post-course knowledge tests, and a final surgical anatomy laboratory practical examination to 22 senior medical students who were enrolled in the course. All students created a final surgical anatomy presentation. RESULTS: The students demonstrated a 100% pass rate in surgical anatomy. The knowledge test, which included assessment of knowledge on perioperative surgical decision making, human physiology, and bedside ultrasound, demonstrated an average improvement of 10%. Statistically significant improvements in median confidence values were identified in 10 of 32 surveyed categories, including surgical skills (p < 0.05); 84% of student goals for the course were achieved. The medical students' surveys confirmed increased confidence related to the use of point-of-care ultrasound, teamwork experience, and basic surgical skills through small group interactive seminars and surgical simulation exercises. CONCLUSION: Our preparation for surgical training course resulted in high student satisfaction and demonstrated an increased sense of confidence to begin surgical training. The 10% improvement in medical student knowledge, as evaluated by a written examination, and the significant improvement in confidence level self-assessment scores confirms this surgery preparation course for senior medical students successfully achieved the desired goals of the course.

Chiari's network: review of the literature.

The Chiari network, present in approximately 2% of the population, and is a reticulated network of fibers originating from the Eustachian connecting to different parts of the right atrium. Its presence results from incomplete reabsorption of the right valve of the sinus venosus. Chiari's network is often clinically insignificant. However, it has been reported to be involved in the pathogenesis of thromboembolic disease, endocarditis, arrhythmias, and entrapment of catheters upon percutaneous intervention. While initially discovered and researched using autopsy dissections, Chiari's network is often found as an incidental finding on diagnostic imaging studies, thus providing new methods for studying its incidence and clinical significance.

Regulation of glucokinase in pancreatic islets by prolactin: a mechanism for increasing glucose-stimulated insulin secretion during pregnancy.

Glucokinase activity is increased in pancreatic islets during pregnancy and in vitro by prolactin (PRL). The underlying mechanisms that lead to increased glucokinase have not been resolved. Since glucose itself regulates glucokinase activity in beta-cells, it was unclear whether the lactogen effects are direct or occur through changes in glucose metabolism. To clarify the roles of glucose metabolism in this process, we examined the interactions between glucose and PRL on glucose metabolism, insulin secretion, and glucokinase expression in insulin 1 (INS-1) cells and rat islets. Although the PRL-induced changes were more pronounced after culture at higher glucose concentrations, an increase in glucose metabolism, insulin secretion, and glucokinase expression occurred even in the absence of glucose. The presence of comparable levels of insulin secretion at similar rates of glucose metabolism from both control and PRL-treated INS-1 cells suggests the PRL-induced increase in glucose metabolism is responsible for the increase in insulin secretion. Similarly, increases in other known PRL responsive genes (e.g. the PRL receptor, glucose transporter-2, and insulin) were also detected after culture without glucose. We show that the upstream glucokinase promoter contains multiple STAT5 binding sequences with increased binding in response to PRL. Corresponding increases in glucokinase mRNA and protein synthesis were also detected. This suggests the PRL-induced increase in glucokinase mRNA and its translation are sufficient to account for the elevated glucokinase activity in beta-cells with lactogens. Importantly, the increase in islet glucokinase observed with PRL is in line with that observed in islets during pregnancy.

Insulin secretagogues, but not glucose, stimulate an increase in [Ca2+]i in the fetal human and porcine beta-cell.

Fetal pancreatic beta-cells release insulin poorly in response to glucose; however, the cellular mechanism for this is unknown. By using fura-2 to measure changes in the cytoplasmic free Ca(2+) concentration in beta-cells, we examined human/porcine fetal islet-like cell clusters (ICCs) and human adult islets for the presence of functional K(+)(ATP) and voltage-activated Ca(2+) ion channels. The effects of glucose, glyceraldehyde, leucine, KCl, and the channel effectors glipizide and BAY K8644 were studied. In fetal human/porcine ICCs and adult islets, KCl, glipizide, and BAY K8644 increased [Ca(2+)](i). Both glucose and glyceraldehyde increased [Ca(2+)](i) in islets but had no effect on ICCs. Leucine increased [Ca(2+)](i) in islets and porcine but not human ICCs. We hypothesize that the beneficial effect of leucine in fetal porcine, but not human ICCs, is attributable to time-dependent maturation of the beta-cells, because porcine ICCs examined were at 87% of the gestational period, and human ICCs were at 42%. Our data demonstrate that both K(+)(ATP) and voltage-activated Ca(2+) channels, required for glucose-stimulated increase in [Ca(2+)](i), are functional early in gestation. This suggests that the cause of the immaturity of fetal human/porcine beta-cells is at a more proximal step of glucose-induced metabolism than the channels on the cell surface.