Amyloid-β efflux from the central nervous system into the plasma

OBJECTIVE

The aim of this study was to measure the flux of amyloid-β (Aβ) across the human cerebral capillary bed to determine whether transport into the blood is a significant mechanism of clearance for Aβ produced in the central nervous system (CNS).

METHODS

Time-matched blood samples were simultaneously collected from a cerebral vein (including the sigmoid sinus, inferior petrosal sinus, and the internal jugular vein), femoral vein, and radial artery of patients undergoing inferior petrosal sinus sampling. For each plasma sample, Aβ concentration was assessed by 3 assays, and the venous to arterial Aβ concentration ratios were determined.

RESULTS

Aβ concentration was increased by ∼7.5% in venous blood leaving the CNS capillary bed compared to arterial blood, indicating efflux from the CNS into the peripheral blood (p < 0.0001). There was no difference in peripheral venous Aβ concentration compared to arterial blood concentration.

INTERPRETATION

Our results are consistent with clearance of CNS-derived Aβ into the venous blood supply with no increase from a peripheral capillary bed. Modeling these results suggests that direct transport of Aβ across the blood-brain barrier accounts for ∼25% of Aβ clearance, and reabsorption of cerebrospinal fluid Aβ accounts for ∼25% of the total CNS Aβ clearance in humans. Ann Neurol 2014;76:837-844.

Responding to SUPPORT: an academic medical center examines its end-of-life care practices. Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments

The purpose of this exploratory study was to examine the end-of-life (EOL) care rendered to patients and families within a large midwestern academic medical center during a recent one-year period. An investigator-developed audit tool was used to review the final hospitalization records of 100 patients. Data were collected regarding demographic variables, final hospitalization, medical diagnoses and histories, and documented end-of-life care. Major findings included a majority of deaths occurring within medical services on critical care units, a frequent short length of stay, a majority of Do Not Resuscitate or Withdrawal of Support orders being written 1-3 days prior to death, an unstable health status prior to admission, and presence of at least one significant chronic illness in the past medical history. Findings are being used to address EOL care related issues within the institution.

Effectiveness of education-screening on cholesterol levels of students

Increases of cholesterol levels from the age of 16 years have been demonstrated in community-based studies. Cholesterol education to students aged 15-17 years in 5 high schools was presented prior to cholesterol screening with the Reflotron. First screening took place in March 1987. An identical program was repeated 11 months later, again followed by screening in March 1988. Of the 5 schools, 2 were assigned to involve teachers. There was a significant cholesterol reduction in these 2 schools, i.e., -17 and -19 mg/dl (p less than 0.05). The effectiveness of the physicians' education and the compliance of the students with the teachers' recommendations certainly must have been enhanced by a different family environment with a higher socioeconomic stratum prevailing in these 2 high schools. However, these factors did not influence the baseline in all 5 schools. In the 3 remaining schools no increases in cholesterol levels expected for this age were observed.