Determination of secretory granule maturation times in pancreatic islet β-cells by serial block-face electron microscopy

It is shown how serial block-face electron microscopy (SBEM) of insulin-secreting β-cells in wild-type mouse pancreatic islets of Langerhans can be used to determine maturation times of secretory granules. Although SBEM captures the β-cell structure at a snapshot in time, the observed ultrastructure can be considered representative of a dynamic equilibrium state of the cells since the pancreatic islets are maintained in culture in approximate homeostasis. It was found that 7.2 ± 1.2% (±st. dev.) of the β-cell volume is composed of secretory granule dense-cores exhibiting angular shapes surrounded by wide (typically ≳100 nm) electron-lucent halos. These organelles are identified as mature granules that store insulin for regulated release through the plasma membrane, with a release time of 96 ± 12 h, as previously obtained from pulsed ³⁵S-radiolabeling of cysteine and methionine. Analysis of β-cell 3D volumes reveals a subpopulation of secretory organelles without electron-lucent halos, identified as immature secretory granules. Another subpopulation of secretory granules is found with thin (typically ≲30 nm) electron-lucent halos, which are attributed to immature granules that are transforming from proinsulin to insulin by action of prohormone convertases. From the volume ratio of proinsulin in the immature granules to insulin in the mature granules, we estimate that the newly formed immature granules remain in morphologically-defined immature states for an average time of 135 ± 14 min, and the immature transforming granules for an average time of 130 ± 17 min.

Single-Electron Detection and Spectroscopy via Relativistic Cyclotron Radiation

It has been understood since 1897 that accelerating charges must emit electromagnetic radiation. Although first derived in 1904, cyclotron radiation from a single electron orbiting in a magnetic field has never been observed directly. We demonstrate single-electron detection in a novel radio-frequency spectrometer. The relativistic shift in the cyclotron frequency permits a precise electron energy measurement. Precise beta electron spectroscopy from gaseous radiation sources is a key technique in modern efforts to measure the neutrino mass via the tritium decay end point, and this work demonstrates a fundamentally new approach to precision beta spectroscopy for future neutrino mass experiments.

Competency champions in the clinical competency committee: a successful strategy to implement milestone evaluations and competency coaching

OBJECTIVES

To create a clinical competency committee (CCC) that (1) centers on the competency-based milestones, (2) is simple to implement, (3) creates competency expertise, and (4) guides remediation and coaching of residents who are not progressing in milestone performance evaluations.

DESIGN

We created a CCC that meets monthly and at each meeting reviews a resident class for milestone performance, a competency (by a faculty competency champion), a resident rotation service, and any other resident or issue of concern.

SETTING

University surgical residency program.

PARTICIPANTS

The CCC members include the program director, associate program directors, director of surgical curriculum, competency champions, departmental chair, 2 at-large faculty members, and the administrative chief residents.

RESULTS

Seven residents were placed on remediation (later renamed as coaching) during the academic year after falling behind on milestone progression in one or more competencies. An additional 4 residents voluntarily placed themselves on remediation for medical knowledge after receiving in-training examination scores that the residents (not the CCC membership) considered substandard. All but 2 of the remediated/coached residents successfully completed all area milestone performance but some chose to stay on the medical knowledge competency strategy.

CONCLUSIONS

Monthly meetings of the CCC make milestone evaluation less burdensome. In addition, the expectations of the residents are clearer and more tangible. "Competency champions" who are familiar with the milestones allow effective coaching strategies and documentation of clear performance improvements in competencies for successful completion of residency training. Residents who do not reach appropriate milestone performance can then be placed in remediation for more formal performance evaluation. The function of our CCC has also allowed us opportunity to evaluate the required rotations to ensure that they offer experiences that help residents achieve competency performance necessary to be safe and effective surgeons upon completion of training.

Long-term follow-up of endovascular abdominal aortic aneurysm repair in a rural veteran patient population

BACKGROUND

The endovascular repair of abdominal aortic aneurysms (EVARs) requires follow-up to detect and treat late complications.

METHODS

Two hundred eleven patients underwent EVAR for infrarenal, nonruptured abdominal aortic aneurysms from 1999 to 2010 at the Raymond G. Murphy VA Medical Center, Albuquerque, NM. A retrospective review examined patient demographics, comorbidities, the distance the patient lived from the facility, early and late complications, and the device implanted. Statistical analysis included the chi-square test for independence, the Fisher exact test, and the 2-sample Mann-Whitney U test for means.

RESULTS

The mean time from the operation to the first complication was 21 months (standard deviation = 20 months) with a mean follow-up of 48 months (standard deviation = 36 months). The late complication rate was 22.8% (54 patients). Sixteen percent did not require any reinterventions, 57% were treated with percutaneous interventions, and 27% required an open surgical procedure. No single comorbidity, combination of comorbidities, distance the patient lived from the facility, or device implanted was predictive of complications.

CONCLUSIONS

EVAR follow-up is essential to detect complications. When complications occur, the majority occur well after the initial treatment, and most can be treated with minimally invasive percutaneous techniques.