Students’ performance of and perspective on an objective structured practical examination for the assessment of preclinical and practical skills in biomedical laboratory science students in Sweden: a 5-year longitudinal study.

Purpose: It aims to find students’ performance of and perspectives on an objective structured practical examination (OSPE) for assessment of laboratory and preclinical skills in biomedical laboratory science (BLS). It also aims to investigate the perception, acceptability, and usefulness of OSPE from the students’ and examiners’ point of view.

Methods: This was a longitudinal study to implement an OSPE in BLS.

On the regulatory importance of 27-hydroxycholesterol in mouse liver.

27-Hydroxycholesterol (27OH) is a strong suppressor of cholesterol synthesis and a weak activator of LXR in vitro. The regulatory importance of 27OH in vivo is controversial. Here we utilized male mice with increased levels of 27OH either due to increased production (CYP27A1 transgenic mice) or reduced metabolism (Cyp7b1-/- mice).

27-hydroxycholesterol mediates negative effects of dietary cholesterol on cognition in mice.

In spite of the fact that cholesterol does not pass the blood-brain barrier, treatment of mice with dietary cholesterol causes significant effects on a number of genes in the brain and in addition a memory impairment. We have suggested that these effects are mediated by 27-hydroxycholesterol, which is able to pass the blood-brain barrier. To test this hypothesis we utilized Cyp27-/- mice lacking 27-hydroxycholesterol.

Is it possible to improve memory function by upregulation of the cholesterol 24S-hydroxylase (CYP46A1) in the brain?

We previously described a heterozygous mouse model overexpressing human HA-tagged 24S-hydroxylase (CYP46A1) utilizing a ubiquitous expression vector. In this study, we generated homozygotes of these mice with circulating levels of 24OH 30-60% higher than the heterozygotes. Female homozygous CYP46A1 transgenic mice, aged 15 months, showed an improvement in spatial memory in the Morris water maze test as compared to the wild type mice.

Sulphatation does not appear to be a protective mechanism to prevent oxysterol accumulation in humans and mice.

24S- and 27-hydroxycholesterol (24OHC and 27OHC) are potent regulators of different biochemical systems in vitro and are the major circulating oxysterols. A small fraction of these oxysterols has been reported to be sulphated but there are no detailed studies. We considered the possibility that sulphatation is a protective mechanism preventing accumulation of free oxysterols.

On the regulatory role of side-chain hydroxylated oxysterols in the brain. Lessons from CYP27A1 transgenic and Cyp27a1(-/-) mice.

The two oxysterols, 27-hydroxycholesterol (27OH) and 24S-hydroxycholesterol (24OH), are both inhibitors of cholesterol synthesis and activators of the liver X receptor (LXR) in vitro. Their role as physiological regulators under in vivo conditions is controversial, however. In the present work, we utilized a previously described mouse model with overexpressed human sterol 27-hydroxylase (CYP27A1).

Bi-lateral changes to hippocampal cholesterol levels during epileptogenesis and in chronic epilepsy following focal-onset status epilepticus in mice.

Brain cholesterol homeostasis has been shown to be disrupted in neurodegenerative conditions such as Alzheimer's and Huntington's diseases. Investigations in animal models of seizure-induced brain injury suggest that brain cholesterol levels are altered by prolonged seizures (status epilepticus) and are a feature of the pathophysiology of temporal lobe epilepsy. The present study measured hippocampal sterol levels in a model of unilateral hippocampal injury triggered by focal-onset status epilepticus, and in chronically epileptic mice.

Proteomic analysis of 14-3-3 zeta binding proteins in the mouse hippocampus.

14-3-3 proteins are ubiquitous molecular chaperones with important roles in brain development and neuronal function. Altered expression of 14-3-3 proteins has been reported in several neurologic and neurodegenerative disorders and identifying 14-3-3 binding proteins may provide important insights into the physiologic and pathophysiologic roles of these proteins. Particular interest has emerged on 14-3-3 zeta (ζ) in the setting of neuronal injury because reducing 14-3-3ζ levels triggers an endoplasmic reticulum stress-like response in neurons and increases vulnerability to excitotoxicity.

Differential diagnosis in patients with suspected bile acid synthesis defects.

Aim: To investigate the clinical presentations associated with bile acid synthesis defects and to describe identification of individual disorders and diagnostic pitfalls.

Methods: Authors describe semiquantitative determination of 16 urinary bile acid metabolites by electrospray ionization-tandem mass spectrometry. Sample preparation was performed by solid-phase extraction.

Side chain-oxidized oxysterols regulate the brain renin-angiotensin system through a liver X receptor-dependent mechanism.

Disturbances in cholesterol metabolism have been associated with hypertension and neurodegenerative disorders. Because cholesterol metabolism in the brain is efficiently separated from plasma cholesterol by the blood-brain barrier (BBB), it is an unsolved paradox how high blood cholesterol can cause an effect in the brain. Here, we discuss the possibility that cholesterol metabolites permeable to the BBB might account for these effects.

The desmosterolosis phenotype: spasticity, microcephaly and micrognathia with agenesis of corpus callosum and loss of white matter.

Desmosterolosis is a rare autosomal recessive disorder of elevated levels of the cholesterol precursor desmosterol in plasma, tissue and cultured cells. With only two sporadic cases described to date with two very different phenotypes, the clinical entity arising from mutations in 24-dehydrocholesterol reductase (DHCR24) has yet to be defined. We now describe consanguineous Bedouin kindred with four surviving affected individuals, all presenting with severe failure to thrive, psychomotor retardation, microcephaly, micrognathia and spasticity with variable degree of hand contractures.

Studies on the cholesterol-free mouse: strong activation of LXR-regulated hepatic genes when replacing cholesterol with desmosterol.

Objective: Characterization of cholesterol homeostasis in male mice with a genetic inactivation of 3beta-hydroxysteroid-delta24-reductase, causing replacement of almost all cholesterol with desmosterol.

Methods And Results: There was an increase in hepatic sterol synthesis and markedly increased fecal loss of neutral sterols. Fecal excretion of bile acids was similar in knockout mice and in controls.

Novel LC-MS/MS method for assay of 7alpha-hydroxy-4-cholesten-3-one in human plasma. Evidence for a significant extrahepatic metabolism.

A new isotope dilution LC-MS/MS method for assay of 7alpha-hydroxy-4-cholesten-3-one without need for derivatization is described. This method was used in catheterization experiments on healthy fasting volunteers. The levels of this generally used marker for bile acid synthesis were slightly but significantly higher in the hepatic vein than in the brachial artery.

Novel route for elimination of brain oxysterols across the blood-brain barrier: conversion into 7alpha-hydroxy-3-oxo-4-cholestenoic acid.

Recently, we demonstrated a net blood-to-brain passage of the oxysterol 27-hydroxycholesterol corresponding to 4-5 mg/day. As the steady-state levels of this sterol are only 1-2 mug/g brain tissue, we hypothesized that it is metabolized and subsequently eliminated from the brain. To explore this concept, we first measured the capacity of in vitro systems representing the major cell populations found in the brain to metabolize 27-hydroxycholesterol.

Isoform- and subcellular fraction-specific differences in hippocampal 14-3-3 levels following experimentally evoked seizures and in human temporal lobe epilepsy.

14-3-3 proteins are a family of signaling molecules involved in diverse cellular functions, which can mediate anti-apoptotic effects. Seizure-induced neuronal death may involve programmed (apoptotic) cell death pathways and is associated with a decline in brain 14-3-3 levels. Presently, we investigated the subcellular localization and effects of seizures on isoforms of 14-3-3 in rat hippocampus, and contrasted these to findings in human temporal lobe epilepsy (TLE).

Studies on the transcriptional regulation of cholesterol 24-hydroxylase (CYP46A1): marked insensitivity toward different regulatory axes.

Mammalian CNS contains a disproportionally large and remarkably stable pool of cholesterol. Despite an efficient recycling there is some requirement for elimination of brain cholesterol. Conversion of cholesterol into 24S-hydroxycholesterol by the cholesterol 24-hydroxylase (CYP46A1) is the quantitatively most important mechanism.

Brain cholesterol synthesis in mice is affected by high dose of simvastatin but not of pravastatin.

On a global scale, there is an increasing tendency for a more aggressive treatment of hypercholesterolemia. Minor effects of statins on brain cholesterol metabolism have been reported in some in vivo animal studies, and it seems that this is due to a local effect of the drug. We treated male mice of the inbred strain C57/BL6 with a high daily dose of lipophilic simvastatin (100 mg/kg b.

Crossing the barrier: net flux of 27-hydroxycholesterol into the human brain.

Side chain oxidized oxysterols have a unique ability to traverse lipophilic membranes. We tested the hypothesis that there is a net flux of 27-hydroxycholesterol from the circulation into the brain using plasma samples collected from the internal jugular vein and an artery of healthy male volunteers. Two independent studies were performed, one in which total levels of 27-hydroxycholesterol were measured and one in which the free fraction of 27-hydroxycholesterol was measured.

Changes in the levels of cerebral and extracerebral sterols in the brain of patients with Alzheimer's disease.

24S-hydroxycholesterol is a side-chain oxidized oxysterol formed in the brain that is continuously crossing the blood-brain barrier to reach the circulation. There may be an opposite flux of 27-hydroxycholesterol, which is formed to a lower extent in the brain than in most other organs. Here we measured cholesterol, lathosterol, 24S- and 27-hydroxycholesterol, and plant sterols in four different brain areas of deceased Alzheimer's disease (AD) patients and controls.