Assessing students' perceptions of the effects of a new Canadian longitudinal pre-clerkship family medicine experience.

BACKGROUND: Despite the implementation of longitudinal community-based pre-clerkship courses in several Canadian medical schools, there is a paucity of data assessing students' views regarding their experiences. The present study sought to measure students' perceived effects of the new Longitudinal Family Medicine Experience (LFME) course at McGill University. METHODS: A 34-item questionnaire called the 'LFME Survey (Student Version)' was created, and all first-year medical students completed it online. RESULTS: The participation rate was 64% (N = 120). Eight factors were identified in the factor analysis performed: overall satisfaction, satisfaction with preceptor, knowledge, affective learning, clinical skills, teaching/feedback, professional identity/professionalism and attitude toward primary care. Factor composite scores were above 4.5/7,indicating that students had positive perceptions of the LFME. Students felt that the LFME was a valuable educational experience and that their preceptors were good role-models. The course improved students' confidence, reinforced their commitment to being a physician and increased their positive attitude toward primary care. INTERPRETATION: Along with similar pre-clerkship courses, the LFME provides a valuable context for developing students' clinical skills, providing real-world cases, teaching patient-centred care and improving attitudes toward primary care. The LFME Survey appears to be a promising and innovative tool that deserves further validation.

Accuracy of episodic autobiographical memory in children with early thyroid hormone deficiency using a staged event.

Autobiographical memory (AM) is a highly constructive cognitive process that often contains memory errors. No study has specifically examined AM accuracy in children with abnormal development of the hippocampus, a crucial brain region for AM retrieval. Thus, the present study investigated AM accuracy in 68 typically and atypically developing children using a staged autobiographical event, the Children's Autobiographical Interview, and structural magnetic resonance imaging. The atypically developing group consisted of 17 children (HYPO) exposed during gestation to insufficient maternal thyroid hormone (TH), a critical substrate for hippocampal development, and 25 children with congenital hypothyroidism (CH), who were compared to 26 controls. Groups differed significantly in the number of accurate episodic details recalled and proportion accuracy scores, with controls having more accurate recollections of the staged event than both TH-deficient groups. Total hippocampal volumes and anterior hippocampal volumes were positively correlated with proportion accuracy scores, but not total accurate episodic details, in HYPO and CH. In addition, greater severity of TH deficiency predicted lower proportion accuracy scores in both HYPO and CH. Overall, these results indicate that children with early TH deficiency have deficits in AM accuracy and that the anterior hippocampus may play a particularly important role in accurate AM retrieval.

Effects of maternal hypothyroidism on offspring hippocampus and memory.

BACKGROUND: Rodents with gestational thyroid-hormone (TH) deficiencies and children with congenital hypothyroidism show abnormal hippocampal development. Given that the human hippocampus starts to develop early in gestation, we asked if children born to women with hypothyroidism during pregnancy also show hippocampal abnormalities and if this is related to the severity of maternal TH insufficiency and current memory functioning. We additionally sought to determine whether effects were more prominent in anterior or posterior hippocampal subsections given these support different memory functions and have different developmental trajectories. We hypothesized that these children would have smaller than normal hippocampal volumes than controls and show memory deficits on both standardized tests and indices of "everyday" memory functioning. METHODS: We studied 54 children aged 9 to 12 years: 30 controls and 24 HYPO cases-offspring from women diagnosed with hypothyroidism prior to or during pregnancy and treated with l-thyroxine. All children received a thorough assessment of memory functions and an MRI scan. For each child, right and left hippocampi were manually traced, and volumes of right and left hippocampi and anterior and posterior segments were determined. RESULTS: HYPO cases showed significantly smaller right and left hippocampal volumes than controls, particularly in right posterior and left anterior segments. In HYPO children, hippocampal volumes were negatively correlated with maternal third-trimester TSH levels and positively correlated with third-trimester fT4. HYPO cases scored significantly below controls on one objective and several subjective memory indices, and these were correlated with hippocampal volumes. CONCLUSION: Early TH insufficiency from maternal hypothyroidism affects offspring hippocampal development and memory.

Neuroplastic effects of music lessons on hippocampal volume in children with congenital hypothyroidism.

Children with congenital hypothyroidism (CH) who experience a neonatal thyroid hormone deficiency have reduced hippocampal volumes compared with healthy controls. Interestingly, evidence suggests that musical training can contribute to structural plasticity in a number of brain areas, including the hippocampus. Therefore, we investigated whether taking music lessons could ameliorate the volumetric reductions of the hippocampus in children with CH. Left and right hippocampal volumes were measured in four groups of children: children with CH with and without music lessons, and healthy controls with and without music lessons. We found that the volume of the right hippocampus was comparable between children with CH who had taken music lessons and the healthy controls. Children with CH who had not taken music lessons had reduced hippocampal volumes compared with the other three groups. These results suggest that music lessons may induce structural neuroplasticity in children with atypical hippocampal development because of early thyroid hormone deficiencies.

Effects of early thyroid hormone deficiency on children's autobiographical memory performance.

Memory deficits and hippocampal abnormalities have been described in individuals with thyroid hormone (TH) insufficiencies; however, no study has yet examined their autobiographical memory (AM) abilities, which are known to be compromised by hippocampal damage. Investigations in adults have shown that AM consists of both episodic and semantic components and that the hippocampus is preferentially involved in episodic AM. The present study used the Children's Autobiographical Interview (CAI) to study episodic and semantic AM in 79 children aged 9 to 14 years, including 26 with early-treated congenital hypothyroidism (CH), 23 born to women with inadequately treated hypothyroidism during pregnancy (HYPO), and 30 typically developing controls. Results showed that relative to controls, CH and HYPO groups both exhibited weaknesses in episodic AM, but not semantic AM. In particular, CH and HYPO groups showed difficulty in recalling event details (i.e., the main happenings) and visual details from past experiences. Overall, this study highlights the importance of TH for early neurodevelopment and provides critical new insight into the effects of early treated TH deficiency on long-term memory performance. Furthermore, the present study indicates that the CAI is an effective tool for investigating episodic AM impairment in clinical pediatric populations.

Episodic and Semantic Autobiographical Memory and Everyday Memory during Late Childhood and Early Adolescence.

Few studies have examined both episodic and semantic autobiographical memory (AM) performance during late childhood and early adolescence. Using the newly developed Children's Autobiographical Interview (CAI), the present study examined the effects of age and sex on episodic and semantic AM and everyday memory in 182 children and adolescents. Results indicated that episodic and semantic AM both improved between 8 and 16 years of age; however, age-related changes were larger for episodic AM than for semantic AM. In addition, females were found to recall more episodic AM details, but not more semantic AM details, than males. Importantly, this sex difference in episodic AM recall was attenuated under conditions of high retrieval support (i.e., the use of probing questions). The ability to clearly visualize past events at the time of recollection was related to children's episodic AM recall performance, particularly the retrieval of perceptual details. Finally, similar age and sex effects were found between episodic AM and everyday memory ability (e.g., memory for everyday activities). More specifically, older participants and females exhibited better episodic AM and everyday memory performance than younger participants and males. Overall, the present study provides important new insight into both episodic and semantic AM performance, as well as the relation between episodic AM and everyday memory, during late childhood and adolescence.

Hippocampal size and memory functioning in children and adolescents with congenital hypothyroidism.

BACKGROUND: Despite early diagnosis and treatment of congenital hypothyroidism (CH) after newborn screening, selective and persistent neurocognitive weaknesses may be seen. One area of particular weakness is memory, especially on tasks known to be mediated by the hippocampus. However, the hippocampus has not been directly studied in this population. OBJECTIVE: Our objective was to use magnetic resonance imaging to determine whether children and adolescents with CH have reduced hippocampal size and abnormal hippocampal growth patterns relative to peers and whether reduced hippocampal volumes in CH predict poor memory performance. METHODS: Studied were 35 CH and 44 typically developing controls aged 9-15 yr. All were assessed using standardized tests of intelligence and verbal and visual memory and received an magnetic resonance imaging scan. Parents completed a questionnaire of their everyday memory functioning (EMF). Right and left hippocampal volumes were measured by manual tracing. RESULTS: CH subjects scored significantly below controls on indices of verbal but not visual memory as well as aspects of EMF. CH subjects also had smaller hippocampal volumes, particularly on the left side. Unlike controls, who showed a positive relationship between age and hippocampal volumes, age was unrelated to hippocampal size in CH. Structure-function correlations revealed significant relationships between hippocampal volumes and EMF in controls and modest correlations between hippocampal volumes and memory test scores but not EMF in CH. CONCLUSIONS: Compromised hippocampal development in CH may contribute to some of the memory weaknesses observed in this population.

Effects of prenatal alcohol exposure on hippocampal volume, verbal learning, and verbal and spatial recall in late childhood.

Children with prenatal alcohol exposure (PAE) show deficits in verbal learning and spatial memory, as well as abnormal hippocampal development. The relationship between their memory and neuroanatomic impairments, however, has not been directly explored. Given that the hippocampus is integral for the synthesis and retrieval of learned information and is particularly vulnerable to the teratogenic effects of alcohol, we assessed whether reduced learning and recall abilities in children with fetal alcohol spectrum disorders (FASDs) are associated with abnormal hippocampal volumes. Nineteen children with FASDs and 18 typically developing controls aged 9 to 15 years were assessed for verbal learning and verbal and spatial recall and underwent structural magnetic resonance imaging. Images were analyzed for total intracranial volume and for right and left hippocampal volumes. Results revealed smaller left hippocampi and poorer verbal learning and verbal and spatial recall performance in children with FASDs than controls, as well as positive correlations between selective memory indices and hippocampal volumes only in the FASD group. Additionally, hippocampal volumes increased significantly with age in controls only, suggesting that PAE may be associated with long-term abnormalities in hippocampal development that may contribute to impaired verbal learning and verbal and spatial recall.

S100B protein is released from rat neonatal neurons, astrocytes, and microglia by in vitro trauma and anti-S100 increases trauma-induced delayed neuronal injury and negates the protective effect of exogenous S100B on neurons.

S100B protein is found in brain, has been used as a marker for brain injury and is neurotrophic. Using a well-characterized in vitro model of brain cell trauma, we have previously shown that strain injury causes S100B release from neonatal rat neuronal plus glial cultures and that exogenous S100B reduces delayed post-traumatic neuronal damage even when given at 6 or 24 h post-trauma. The purpose of the current studies was to measure post-traumatic S100B release by specific brain cell types and to examine the effect of an antibody to S100 on post-traumatic delayed (48 h) neuronal injury and the protective effect of exogenous S100B. Neonatal rat cortical cells grown on a deformable elastic membrane were subjected to a strain (stretch) injury produced by a 50 ms displacement of the membrane. S100B was measured with an ELISA kit. Trauma released S100B from pure cultures of astrocytes, microglia, and neurons. Anti-S100 reduced released S100B to below detectable levels, increased delayed neuronal injury in traumatized cells and negated the protective effect of exogenous S100B on injured cells. Heat denatured anti-S100 did not exacerbate injury. These studies provide further evidence for a protective role for S100B following neuronal trauma.

S100B protein is released by in vitro trauma and reduces delayed neuronal injury.

S100B protein in brain is produced primarily by astrocytes, has been used as a marker for brain injury and has also been shown to be neurotrophic and neuroprotective. Using a well characterized in vitro model of brain cell trauma, we examined the potential role of exogenous S100B in preventing delayed neuronal injury. Neuronal plus glial cultures were grown on a deformable Silastic membrane and then subjected to strain (stretch) injury produced by a 50 ms displacement of the membrane. We have previously shown that this injury causes an immediate, but transient, nuclear uptake of the fluorescent dye propidium iodide by astrocytes and a 24-48 h delayed uptake by neurons. Strain injury caused immediate release of S100-beta with further release by 24 and 48 h. Adding 10 or 100 nm S100B to injured cultures at 15 s, 6 h or 24 h after injury reduced delayed neuronal injury measured at 48 h. Exogenous S100B was present in the cultures through 48 h. These studies directly demonstrate the release and neuroprotective role of S100B after traumatic injury and that, unlike most receptor antagonists used for the treatment of trauma, S100B is neuroprotective when given at later, more therapeutically relevant time points.

Group I metabotropic receptor antagonism blocks depletion of calcium stores and reduces potentiated capacitative calcium entry in strain-injured neurons and astrocytes.

Antagonism of the group I metabotropic receptor subtype 1 (mGluR1) with (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA) has been shown to reduce deficits after in vivo or in vitro traumatic brain injury. We have previously demonstrated that AIDA prevents elevation of astrocyte IP3 subsequent to injury-induced activation of mGluRs and phospholipase C. Since IP3 can cause release of intracellular Ca2+ stores we tested the hypothesis that pre- or post-injury treatment with AIDA can affect (1) the depletion of Ca2+ stores which occurs soon after strain injury of cultured neurons and astrocytes and (2) the delayed potentiation of capacitative calcium entry in strain-injured neurons. Astrocyte or neuronal plus glial cultures were grown on Silastic membranes that were subjected to a 50-msec pulse of compressed gas, which caused membrane displacement and biaxial strain (stretch) injury of the adhering cells. Cells were treated 10 min before or immediately after injury with 100 microM AIDA and the intracellular free Ca2+ ([Ca2+]i) response to thapsigargin, which inhibits the ability of the stores to sequester Ca2+, was measured at 15 min or 3 h after injury. AIDA pre- or post-injury treatment prevented the depletion of intracellular calcium stores at 15 min post-injury in astrocytes and neurons and reduced the potentiated neuronal capacitative calcium influx 3 h after injury. Since Ca2+ and Ca2+ stores influence many factors, including neuronal excitability, plasticity, protein synthesis, and neuronal-glial interactions, prevention of Ca2+ store depletion and subsequent exaggerated capacitative calcium entry may be an important subcellular mechanism by which antagonism of mGluR1 receptors exert an injury-reducing effect. More globally, the results further emphasize the importance of altered signaling and calcium regulatory mechanisms in the immediate and delayed sequelae of traumatic brain injury.

Antagonism of group I metabotropic glutamate receptors and PLC attenuates increases in inositol trisphosphate and reduces reactive gliosis in strain-injured astrocytes.

We have previously found that in vitro traumatic injury uncouples IP3-mediated intracellular free calcium ([Ca2+]i) signaling in astrocytes (Rzigalinski et al., 1998; Floyd et al., 2001). Since Group I metabotropic glutamate receptors (mGluRs) are coupled to IP3-mediated Ca2+ signaling, we investigated their role in the in vitro strain injury of cultured astrocytes. Astrocytes grown on Silastic membranes were labeled with 3H-myo-inositol and strain (stretch)-injured. Cells injured in the presence of LiCl to prevent inositol phosphate metabolism were acid extracted and inositol phosphates (IPx) isolated using anion exchange columns. Reactive gliosis was assessed as increased glial fibrillary acidic protein immunoreactivity (GFAP-IR). Pre- but not post-injury administration of (RS)-1-aminoindan-15-decarboxylic acid (AIDA) or (S)-4-carboxy-3-hydroxyphenylglycine (S4CH3HPG), both group I mGluR antagonists, attenuated injury-induced increases in IPx. Injury increased GFAP-IR in astrocytes at 24 and 48 h post injury, which was reduced or blocked by AIDA or inhibition of phospholipase C (PLC) with U73122. These findings suggest that strain injury activates Group I mGluRs, causing aberrant IPx production and uncoupling of the PLC signaling pathway. Changes in this signaling pathway may be related to induction of reactive gliosis. Additionally, our results suggest a complex physical coupling between G protein receptor, PLC, and IP3 receptor, in support of the conformational coupling model.

Activation of extracellular signal-regulated kinase by stretch-induced injury in astrocytes involves extracellular ATP and P2 purinergic receptors.

Gliosis is characterized by hypertrophic and hyperplastic responses of astrocytes to brain injury. To determine whether injury of astrocytes produced by an in vitro model of brain trauma activates extracellular signal-regulated protein kinase (ERK), a key regulator of cellular proliferation and differentiation, astrocytes cultured on deformable SILASTIC membranes were subjected to rapid, reversible strain (stretch)-induced injury. Activation of ERK was observed 1 min after injury, was maximal from 10 to 30 min, and remained elevated for 3 hr. Activation of ERK was dependent on the rate and magnitude of injury; maximum ERK activation was observed after a 20-60 msec, 7.5 mm membrane displacement. ERK activation was blocked by inhibiting MEK, the upstream activator of ERK. Activation of ERK was reduced when calcium influx was diminished. When extracellular ATP was hydrolyzed by apyrase or ATP/P2 receptors were blocked, injury-induced ERK activation was significantly reduced. P2 receptor antagonist studies indicated a role for P2X2 and P2Y1, but not P2X1, P2X3, or P2X7, receptors in injury-induced ERK activation. These findings demonstrate for the first time that ATP released by mechanical injury is one of the signals that triggers ERK activation and suggest a role for extracellular ATP, P2 purinergic receptors, and calcium-dependent ERK signaling in the astrocytic response to brain trauma.

NMDA receptor activation contributes to a portion of the decreased mitochondrial membrane potential and elevated intracellular free calcium in strain-injured neurons.

In our previous studies, we have shown that in vitro biaxial strain (stretch) injury of neurons in neuronal plus glial cultures increases intracellular free calcium ([Ca(2+)](i)) and decreases mitochondrial membrane potential (deltapsi(m)). The goal of this study was to determine whether strain injury, without the addition of exogenous agents, causes glutamate release, and whether NMDA receptor antagonists affect the post-strain injury rise in [Ca(2+)](i) and decrease in deltapsi(m). [Ca(2+)](i) and deltapsi(m) were measured using the fluorescent indicators fura-2 AM and rhodamine-1,2,3 (rh123). Strain injury of neuronal plus glial cultures caused an immediate 100-200 nM elevation in neuronal [Ca(2+)]i and a decline in neuronal deltapsi(m) by 15 min post-injury. Pretreatment with the NMDA receptor antagonist MK-801 (10 microM) attenuated the [Ca(2+)](i) elevation after mild, but not moderate and severe injury. MK-801 pretreatment reduced the decline in deltapsi(m) after mild and moderate, but not after severe injury. The NMDA receptor antagonist D-2-amino-5-phosphonopentanoic acid (APV; 100 microM) had effects similar to MK-801. Simultaneous measurement of [Ca(2+)](i) and deltapsi(m) demonstrated a significant correlation and a temporal relationship between [Ca(2+)](i) elevation and depression of deltapsi(m). We conclude that NMDA receptor stimulation contributes to some of the changes in [Ca(2+)](i) and deltapsi(m) after less severe strain injury. However, after more pronounced injury other mechanisms appear to be more involved.