Lifestyle and vascular risk effects on MRI-based biomarkers of Alzheimer's disease: a cross-sectional study of middle-aged adults from the broader New York City area

OBJECTIVE

To investigate the effects of lifestyle and vascular-related risk factors for Alzheimer's disease (AD) on in vivo MRI-based brain atrophy in asymptomatic young to middle-aged adults.

DESIGN

Cross-sectional, observational.

SETTING

Broader New York City area. Two research centres affiliated with the Alzheimer's disease Core Center at New York University School of Medicine.

PARTICIPANTS

We studied 116 cognitively normal healthy research participants aged 30-60 years, who completed a three-dimensional T1-weighted volumetric MRI and had lifestyle (diet, physical activity and intellectual enrichment), vascular risk (overweight, hypertension, insulin resistance, elevated cholesterol and homocysteine) and cognition (memory, executive function, language) data. Estimates of cortical thickness for entorhinal (EC), posterior cingulate, orbitofrontal, inferior and middle temporal cortex were obtained by use of automated segmentation tools. We applied confirmatory factor analysis and structural equation modelling to evaluate the associations between lifestyle, vascular risk, brain and cognition.

RESULTS

Adherence to a Mediterranean-style diet (MeDi) and insulin sensitivity were both positively associated with MRI-based cortical thickness (diet: β_s≥0.26, insulin sensitivity β_s≥0.58, P≤0.008). After accounting for vascular risk, EC in turn explained variance in memory (P≤0.001). None of the other lifestyle and vascular risk variables were associated with brain thickness. In addition, the path associations between intellectual enrichment and better cognition were significant (β_s≥0.25 P≤0.001), as were those between overweight and lower cognition (β_s≥-0.22, P≤0.01).

CONCLUSIONS

In cognitively normal middle-aged adults, MeDi and insulin sensitivity explained cortical thickness in key brain regions for AD, and EC thickness predicted memory performance in turn. Intellectual activity and overweight were associated with cognitive performance through different pathways. Our findings support further investigation of lifestyle and vascular risk factor modification against brain ageing and AD. More studies with larger samples are needed to replicate these research findings in more diverse, community-based settings.

Electro-mechanical response of a 3D nerve bundle model to mechanical loads leading to axonal injury

Traumatic brain injuries and damage are major causes of death and disability. We propose a 3D fully coupled electro-mechanical model of a nerve bundle to investigate the electrophysiological impairments due to trauma at the cellular level. The coupling is based on a thermal analogy of the neural electrical activity by using the finite element software Abaqus CAE 6.13-3. The model includes a real-time coupling, modulated threshold for spiking activation, and independent alteration of the electrical properties for each 3-layer fibre within a nerve bundle as a function of strain. Results of the coupled electro-mechanical model are validated with previously published experimental results of damaged axons. Here, the cases of compression and tension are simulated to induce (mild, moderate, and severe) damage at the nerve membrane of a nerve bundle, made of 4 fibres. Changes in strain, stress distribution, and neural activity are investigated for myelinated and unmyelinated nerve fibres, by considering the cases of an intact and of a traumatised nerve membrane. A fully coupled electro-mechanical modelling approach is established to provide insights into crucial aspects of neural activity at the cellular level due to traumatic brain injury. One of the key findings is the 3D distribution of residual stresses and strains at the membrane of each fibre due to mechanically induced electrophysiological impairments, and its impact on signal transmission.

Electro-mechanical response of a 3D nerve bundle model to mechanical loads leading to axonal injury

Axonal damage is one of the most common pathological features of traumatic brain injury, leading to abnormalities in signal propagation for nervous systems. We present a 3D fully coupled electro-mechanical model of a nerve bundle, made with the finite element software Abaqus 6.13-3. The model includes a real-time coupling, modulated threshold for spiking activation and independent alteration of the electrical properties for each 3-layer fibre within the bundle. Compression and tension are simulated to induce damage at the nerve membrane. Changes in strain, stress distribution and neural activity are investigated for myelinated and unmyelinated nerve fibres, by considering the cases of an intact and of a traumatized nerve membrane. Results show greater changes in transmitting action potential in the myelinated fibre.

Perimenopause and emergence of an Alzheimer's bioenergetic phenotype in brain and periphery

After advanced age, female sex is the major risk factor for Alzheimer’s disease (AD). The biological mechanisms underlying the increased AD risk in women remain largely undetermined. Preclinical studies identified the perimenopause to menopause transition, a neuroendocrine transition state unique to the female, as a sex-specific risk factor for AD. In animals, estrogenic regulation of cerebral glucose metabolism (CMRglc) falters during perimenopause. This is evident in glucose hypometabolism and decline in mitochondrial efficiency which is sustained thereafter. This study bridges basic to clinical science to characterize brain bioenergetics in a cohort of forty-three, 40–60 year-old clinically and cognitively normal women at different endocrine transition stages including premenopause (controls, CNT, n = 15), perimenopause (PERI, n = 14) and postmenopause (MENO, n = 14). All participants received clinical, laboratory and neuropsychological examinations, ¹⁸F-fluoro-deoxyglucose (FDG)-Positron Emission Tomography (PET) FDG-PET scans to estimate CMRglc, and platelet mitochondrial cytochrome oxidase (COX) activity measures. Statistical parametric mapping and multiple regression models were used to examine clinical, CMRglc and COX data across groups. As expected, the MENO group was older than PERI and controls. Groups were otherwise comparable for clinical measures and distribution of APOE4 genotype. Both MENO and PERI groups exhibited reduced CMRglc in AD-vulnerable regions which was correlated with decline in mitochondrial COX activity compared to CNT (p’s<0.001). A gradient in biomarker abnormalities was most pronounced in MENO, intermediate in PERI, and lowest in CNT (p<0.001). Biomarkers correlated with immediate and delayed memory scores (Pearson’s 0.26≤r≤0.32, p≤0.05). These findings validate earlier preclinical findings and indicate emergence of bioenergetic deficits in perimenopausal and postmenopausal women, suggesting that the optimal window of opportunity for therapeutic intervention in women is early in the endocrine aging process.

Sex differences in Alzheimer risk: Brain imaging of endocrine vs chronologic aging

OBJECTIVE

This observational multimodality brain imaging study investigates emergence of endophenotypes of late-onset Alzheimer disease (AD) risk during endocrine transition states in a cohort of clinically and cognitively normal women and age-matched men.

METHODS

Forty-two 40- to 60-year-old cognitively normal women (15 asymptomatic perimenopausal by age [CNT], 13 perimenopausal [PERI], and 14 postmenopausal [MENO]) and 18 age- and education-matched men were examined. All patients had volumetric MRI, ¹⁸F-fluoro-2-deoxyglucose (FDG)-PET (glucose metabolism), and Pittsburgh compound B-PET scans (β-amyloid [Aβ] deposition, a hallmark of AD pathology).

RESULTS

As expected, the MENO group was older than the PERI and CNT groups. Otherwise, groups were comparable on clinical and neuropsychological measures and APOE4 distribution. Compared to CNT women and to men, and controlling for age, PERI and MENO groups exhibited increased indicators of AD endophenotype, including hypometabolism, increased Aβ deposition, and reduced gray and white matter volumes in AD-vulnerable regions (p < 0.001). AD biomarker abnormalities were greatest in MENO, intermediate in PERI, and lowest in CNT women (p < 0.001). Aβ deposition was exacerbated in APOE4-positive MENO women relative to the other groups (p < 0.001).

CONCLUSIONS

Multimodality brain imaging indicates sex differences in development of the AD endophenotype, suggesting that the preclinical AD phase is early in the female aging process and coincides with the endocrine transition of perimenopause. These data indicate that the optimal window of opportunity for therapeutic intervention in women is early in the endocrine aging process.

Effects of vascular risk factors, statins, and antihypertensive drugs on PiB deposition in cognitively normal subjects

INTRODUCTION

Hypertension, hypercholesterolemia, and obesity increase the risk of dementia. Although their detection is commonly followed by an introduction of treatment, little is known about how medications frequently used to treat vascular risk affect amyloid deposition.

METHODS

A cross-sectional study of 156 subjects who underwent positron emission tomography with PiB. Using linear regression, we tested whether blood pressure, cholesterol, overweight/obese status, angiotensin receptor blockers (ARBs), beta-blockers, diuretics, angiotensin converting enzyme inhibitors, and statins predicted amyloid deposition.

RESULTS

The use of ARBs (β = -.15, P = .044) and diuretics (β = -.20, P = .006) predicted less amyloid accumulation; older age (β = .29, P < .001) and statins (β = .23, P = .004) were related to greater amyloid deposition. Overweight and/or obese women had more cortical amyloid than their peers.

DISCUSSION

Prospective studies should confirm effects of drugs and increased body weight on amyloid accumulation and establish whether they translate into measurable clinical outcomes. Women may be more susceptible to harmful effects of obesity.

Nutrient patterns and brain biomarkers of Alzheimer's disease in cognitively normal individuals

OBJECTIVES

Epidemiological evidence linking diet, one of the most important modifiable lifestyle factors, and risk of Alzheimer's disease (AD) is rapidly increasing. However, there is little or no evidence for a direct association between dietary nutrients and brain biomarkers of AD. This study identifies nutrient patterns associated with major brain AD biomarkers in a cohort of clinically and cognitively normal (NL) individuals at risk for AD.

DESIGN

Cross-sectional study.

SETTING

Manhattan (broader area).

PARTICIPANTS

Fifty-two NL individuals (age 54+12 y, 70% women, Clinical Dementia Rating=0, MMSE>27, neuropsychological test performance within norms by age and education) with complete dietary information and cross-sectional, 3D T1-weighted Magnetic Resonance Imaging (MRI; gray matter volumes, GMV, a marker of brain atrophy), 11C-Pittsburgh compound-B (PiB; a marker of fibrillar amyloid-β, Aβ) and 18F-fluorodeoxyglucose (FDG; a marker of glucose metabolism, METglc) Positron Emission Tomography (PET) scans were examined.

MEASUREMENTS

Dietary intake of 35 nutrients associated with cognitive function and AD was assessed using the Harvard/Willet Food Frequency Questionnaire. Principal component analysis was used to generate nutrient patterns (NP) from the full nutrient panel. Statistical parametric mapping and voxel based morphometry were used to assess the associations of the identified NPs with AD biomarkers.

RESULTS

None of the participants were diabetics, smokers, or met criteria for obesity. Five NPs were identified: NP1 was characterized by most B-vitamins and several minerals [VitB and Minerals]; NP2 by monounsaturated and polyunsaturated fats, including ω-3 and ω-6 PUFA, and vitamin E [VitE and PUFA]; NP3 by vitamin A, vitamin C, carotenoids and dietary fibers [Anti-oxidants and Fibers]; NP4 by vitamin B12, vitamin D and zinc [VitB12 and D]; NP5 by saturated, trans-saturated fats, cholesterol and sodium [Fats]. Voxel-based analysis showed that NP4 scores [VitB12 and D] were positively associated with METglc and GMV, and negatively associated with PiB retention in AD-vulnerable regions (p<0.001). In addition, both METglc and GMV were positively associated with NP2 scores [VitE and PUFA], and negatively associated with NP5 scores [Fats] (p<0.001), and METglc was positively associated with higher NP3 scores [Anti-oxidants and Fibers] (p<0.001). Adjusting for age, gender, ethnicity, education, caloric intake, BMI, alcohol consumption, family history and Apolipoprotein E (APOE) status did not attenuate these relationships. The identified 'AD-protective' nutrient combination was associated with higher intake of fresh fruit and vegetables, whole grains, fish and low-fat dairies, and lower intake of sweets, fried potatoes, high-fat dairies, processed meat and butter.

CONCLUSION

Specific dietary NPs are associated with brain biomarkers of AD in NL individuals, suggesting that dietary interventions may play a role in the prevention of AD by modulating AD-risk through its effects on Aβ and associated neuronal impairment.

Periodontal disease associates with higher brain amyloid load in normal elderly

The accumulation of amyloid-β (Aβ) plaques is a central feature of Alzheimer's disease (AD). First reported in animal models, it remains uncertain if peripheral inflammatory and/or infectious conditions in humans can promote Aβ brain accumulation. Periodontal disease, a common chronic infection, has been previously reported to be associated with AD. Thirty-eight cognitively normal, healthy, and community-residing elderly (mean age, 61 and 68% female) were examined in an Alzheimer's Disease Research Center and a University-Based Dental School. Linear regression models (adjusted for age, apolipoprotein E, and smoking) were used to test the hypothesis that periodontal disease assessed by clinical attachment loss was associated with brain Aβ load using (11)C-Pittsburgh compound B (PIB) positron emission tomography imaging. After adjusting for confounders, clinical attachment loss (≥3 mm), representing a history of periodontal inflammatory/infectious burden, was associated with increased PIB uptake in Aβ vulnerable brain regions (p = 0.002). We show for the first time in humans an association between periodontal disease and brain Aβ load. These data are consistent with the previous animal studies showing that peripheral inflammation/infections are sufficient to produce brain Aβ accumulations.

Reduced retention of Pittsburgh compound B in white matter lesions

PURPOSE

One of the interesting features of the amyloid tracer Pittsburgh compound B (PiB) is that it generates a signal in the white matter (WM) in both healthy subjects and cognitively impaired individuals. This characteristic gave rise to the possibility that PiB could be used to trace WM pathology. In a group of cognitively healthy elderly we examined PiB retention in normal-appearing WM (NAWM) and WM lesions (WML), one of the most common brain pathologies in aging.

METHODS

We segmented WML and NAWM on fluid attenuation inversion recovery (FLAIR) images of 73 subjects (age 61.9 ± 10.0, 71 % women). PiB PET images were corrected for partial volume effects and coregistered to FLAIR images and WM masks. WML and NAWM PiB signals were then extracted.

RESULTS

PiB retention in WML was lower than in NAWM (p < 0.001, 14.6 % reduction). This was true both for periventricular WML (p < 0.001, 17.8 % reduction) and deep WML (p = 0.001, 7.5 % reduction).

CONCLUSION

PiB binding in WM is influenced by the presence of WML, which lower the signal. Our findings add to the growing evidence that PiB can depict WM pathology and should prompt further investigations into PiB binding targets in WM.

Reduced glucose uptake and Aβ in brain regions with hyperintensities in connected white matter

Interstitial concentration of amyloid beta (Aß) is positively related to synaptic activity in animal experiments. In humans, Aß deposition in Alzheimer's disease overlaps with cortical regions highly active earlier in life. White matter lesions (WML) disrupt connections between gray matter (GM) regions which in turn changes their activation patterns. Here, we tested if WML are related to Aß accumulation (measured with PiB-PET) and glucose uptake (measured with FDG-PET) in connected GM. WML masks from 72 cognitively normal (age 61.7 ± 9.6 years, 71% women) individuals were obtained from T2-FLAIR. MRI and PET images were normalized into common space, segmented and parcellated into gray matter (GM) regions. The effects of WML on connected GM regions were assessed using the Change in Connectivity (ChaCo) score. Defined for each GM region, ChaCo is the percentage of WM tracts connecting to that region that pass through the WML mask. The regional relationship between ChaCo, glucose uptake and Aß was explored via linear regression. Subcortical regions of the bilateral caudate, putamen, calcarine, insula, thalamus and anterior cingulum had WM connections with the most lesions, followed by frontal, occipital, temporal, parietal and cerebellar regions. Regional analysis revealed that GM with more lesions in connecting WM and thus impaired connectivity had lower FDG-PET (r = 0.20, p<0.05 corrected) and lower PiB uptake (r = 0.28, p<0.05 corrected). Regional regression also revealed that both ChaCo (β = 0.045) and FDG-PET (β = 0.089) were significant predictors of PiB. In conclusion, brain regions with more lesions in connecting WM had lower glucose metabolism and lower Aß deposition.

Nutrient intake and brain biomarkers of Alzheimer's disease in at-risk cognitively normal individuals: a cross-sectional neuroimaging pilot study

OBJECTIVE

There is increasing evidence to suggest that diet, one of the most important modifiable environmental factors, may play a role in preventing or delaying cognitive decline and Alzheimer's disease (AD). This study examines the relationship between dietary nutrients and brain biomarkers of AD in cognitively normal individuals (NL) with and without AD risk factors.

DESIGN

As part of an ongoing brain imaging study, participants received clinical and laboratory examinations, a neurocognitive test battery, positron emission tomography (PET) with (11)C-Pittsburgh Compound-B (PiB; a measure of amyloid-β (Aβ) load) and (18)F-fluorodeoxyglucose (FDG; a proxy of neuronal activity), and completed semiquantitative food frequency questionnaires.

SETTING

Research centre affiliated with the Alzheimer's disease Core Center at New York University School of Medicine.

PARTICIPANTS

49 NL individuals (age 25-72 years, 69% women) with dietary information, (11)C-PiB and (18)F-FDG PET scans were examined.

RESULTS

Controlling for age and total caloric intake, higher intake of vitamin B12, vitamin D and ω-3 polyunsaturated fatty acid (PUFA) was associated with lower Aβ load in AD regions on PiB-PET, while higher intake of β-carotene and folate was associated with higher glucose metabolism on FDG-PET. β-carotene and folate were associated with reduced glucose metabolism for women, apolipoprotein E epsilon 4 (APOE4) carriers and participants with positive AD family history, but not for their risk-free counterparts. The associations of vitamin B12, vitamin D and ω-3 PUFA with PiB retention were independent of gender, APOE and family history. The identified nutrient combination was associated with higher intake of vegetables, fruit, whole grains, fish and legumes, and lower intake of high-fat dairies, meat and sweets.

CONCLUSIONS

Our data provide a potential pathophysiological mechanism for epidemiological findings showing that dietary interventions may play a role in the prevention of AD. Longitudinal studies are needed to determine whether there is a direct link between nutrient intake, brain biomarkers and risk of AD.

Mediterranean Diet and Magnetic Resonance Imaging-Assessed Brain Atrophy in Cognitively Normal Individuals at Risk for Alzheimer's Disease

OBJECTIVES

Epidemiological evidence linking diet, one of the most important modifiable environmental factors, and risk of Alzheimer's disease (AD) is rapidly increasing. Several studies have shown that higher adherence to a Mediterranean diet (MeDi) is associated with reduced risk of AD. This study examines the associations between high vs. lower adherence to a MeDi and structural MRI-based brain atrophy in key regions for AD in cognitively normal (NL) individuals with and without risk factors for AD.

DESIGN

Cross-sectional study.

SETTING

Manhattan (broader area).

PARTICIPANTS

Fifty-two NL individuals (age 54+12 y, 70% women) with complete dietary information and cross-sectional, 3D T1-weighted MRI scans were examined.

MEASUREMENTS

Subjects were dichotomized into those showing higher vs. lower adherences to the MeDi using published protocols. Estimates of cortical thickness for entorhinal cortex (EC), inferior parietal lobe, middle temporal gyrus, orbitofrontal cortex (OFC) and posterior cingulate cortex (PCC) were obtained by use of automated segmentation tools (FreeSurfer). Multivariate general linear models and linear regressions assessed the associations of MeDi with MRI measures.

RESULTS

Of the 52 participants, 20 (39%) showed higher MeDi adherence (MeDi+) and 32 (61%) showed lower adherence (MeDi-). Groups were comparable for clinical, neuropsychological measures, presence of a family history of AD (FH), and frequency of Apolipoprotein E (APOE) ε4 genotype. With and without controlling for age and total intracranial volume, MeDi+ subjects showed greater thickness of AD-vulnerable ROIs as compared to MeDi- subjects (Wilk's Lambda p=0.026). Group differences were most pronounced in OFC (p=0.001), EC (p=0.03) and PCC (p=0.04) of the left hemisphere. Adjusting for gender, education, FH, APOE status, BMI, insulin resistance scores and presence of hypertension did not attenuate the relationship.

CONCLUSION

NL individuals showing lower adherence to the MeDi had cortical thinning in the same brain regions as clinical AD patients compared to those showing higher adherence. These data indicate that the MeDi may have a protective effect against tissue loss, and suggest that dietary interventions may play a role in the prevention of AD.

A conceptual framework for research on subjective cognitive decline in preclinical Alzheimer's disease

There is increasing evidence that subjective cognitive decline (SCD) in individuals with unimpaired performance on cognitive tests may represent the first symptomatic manifestation of Alzheimer's disease (AD). The research on SCD in early AD, however, is limited by the absence of common standards. The working group of the Subjective Cognitive Decline Initiative (SCD-I) addressed this deficiency by reaching consensus on terminology and on a conceptual framework for research on SCD in AD. In this publication, research criteria for SCD in pre-mild cognitive impairment (MCI) are presented. In addition, a list of core features proposed for reporting in SCD studies is provided, which will enable comparability of research across different settings. Finally, a set of features is presented, which in accordance with current knowledge, increases the likelihood of the presence of preclinical AD in individuals with SCD. This list is referred to as SCD plus.

Brain imaging of cognitively normal individuals with 2 parents affected by late-onset AD

OBJECTIVES

This brain imaging study examines whether cognitively normal (NL) individuals with 2 parents affected by late-onset Alzheimer disease (LOAD) show evidence of more extensive Alzheimer disease pathology compared with those who have a single parent affected by LOAD.

METHODS

Fifty-two NL individuals received MRI, (11)C-Pittsburgh compound B (PiB)-PET, and (18)F-fluoro-2-deoxyglucose (FDG)-PET. These included 4 demographically balanced groups (n = 13/group, aged 32-72 years, 60% female, 30% APOE ε4 carriers) of NL individuals with maternal (FHm), paternal (FHp), and maternal and paternal (FHmp) family history of LOAD, and with negative family history (FH-). Statistical parametric mapping, voxel-based morphometry, and z-score mapping were used to compare MRI gray matter volumes (GMVs), partial volume-corrected PiB retention, and FDG metabolism across FH groups and vs FH-.

RESULTS

NL FHmp showed more severe abnormalities in all 3 biomarkers vs the other groups regarding the number of regions affected and magnitude of impairment. PiB retention and hypometabolism were most pronounced in FHmp, intermediate in FHm, and lowest in FHp and FH-. GMV reductions were highest in FHmp and intermediate in FHm and FHp vs FH-. In all FH+ groups, amyloid-β deposition exceeded GMV loss and hypometabolism exceeded GMV loss (p < 0.001), while amyloid-β deposition exceeded hypometabolism in FHmp and FHp but not in FHm.

CONCLUSIONS

These biomarker findings show a "LOAD parent-dose effect" in NL individuals several years, if not decades, before possible clinical symptoms.

FDG and Amyloid PET in Cognitively Normal Individuals at Risk for Late-Onset Alzheimer's Disease

Having a parent affected by late-onset Alzheimer’s disease (AD) is a major risk factor for cognitively normal (NL) individuals. This study explores the potential of PET with ¹⁸F-FDG and the amyloid- β (Aβ) tracer ¹¹C-Pittsburgh Compound B (PiB) for detection of individual risk in NL adults with AD-parents.

Physical Activity, Mediterranean Diet and Biomarkers-Assessed Risk of Alzheimer's: A Multi-Modality Brain Imaging Study

Increased physical activity and higher adherence to a Mediterranean-type diet (MeDi) have been independently associated with reduced risk of Alzheimer's disease (AD). Their association has not been investigated with the use of biomarkers. This study examines whether, among cognitively normal (NL) individuals, those who are less physically active and show lower MeDi adherence have brain biomarker abnormalities consistent with AD.

METHODS

Forty-five NL individuals (age 54 ± 11, 71% women) with complete leisure time physical activity (LTA), dietary information, and cross-sectional 3D T1-weigthed MRI, ¹¹C-Pittsburgh Compound B (PiB) and ¹⁸F-fluorodeoxyglucose (FDG) Positron Emission Tomography (PET) scans were examined. Voxel-wise multivariate partial least square (PLS) regression was used to examine the effects of LTA, MeDi and their interaction on brain biomarkers. Age, gender, ethnicity, education, caloric intake, BMI, family history of AD, Apolipoprotein E (APOE) genotype, presence of hypertension and insulin resistance were examined as confounds. Subjects were dichotomized into more and less physically active (LTA+ vs. LTA-; n = 21 vs. 24), and into higher vs. lower MeDi adherence groups (n = 18 vs. 27) using published scoring methods. Spatial patterns of brain biomarkers that represented the optimal association between the images and the groups were generated for all modalities using voxel-wise multivariate Partial Least Squares (PLS) regression.

RESULTS

Groups were comparable for clinical and neuropsychological measures. Independent effects of LTA and MeDi factors were observed in AD-vulnerable brain regions for all modalities (p < 0.001). Increased AD-burden (in particular higher Aβ load and lower glucose metabolism) were observed in LTA- compared to LTA+ subjects, and in MeDi- as compared to MeDi+ subjects. A gradient effect was observed for all modalities so that LTA-/MeDi- subjects had the highest and LTA+/MeDi+ subjects had the lowest AD-burden (p < 0.001), although the LTA × MeDi interaction was significant only for FDG measures (p < 0.03). Adjusting for covariates did not attenuate these relationships.

CONCLUSION

Lower physical activity and MeDi adherence were associated with increased brain AD-burden among NL individuals, indicating that lifestyle factors may modulate AD risk. Studies with larger samples and longitudinal evaluations are needed to determine the predictive power of the observed associations.

MEDITERRANEAN DIET AND MAGNETIC RESONANCE IMAGING-ASSESSED BRAIN ATROPHY IN COGNITIVELY NORMAL INDIVIDUALS AT RISK FOR ALZHEIMER’S DISEASE

OBJECTIVES: Epidemiological evidence linking diet, one of the most important modifiable environmental factors, and risk of Alzheimer’s disease (AD) is rapidly increasing. Several studies have shown that higher adherence to a Mediterranean diet (MeDi) is associated with reduced risk of AD. This study examines the associations between high vs. lower adherence to a MeDi and structural MRI-based brain atrophy in key regions for AD in cognitively normal (NL) individuals with and without risk factors for AD. DESIGN: Cross-sectional study. SETTING: Manhattan (broader area). PARTICIPANTS: Fifty-two NL individuals (age 54+12 y, 70% women) with complete dietary information and cross-sectional, 3D T1-weighted MRI scans were examined. MEASUREMENTS: Subjects were dichotomized into those showing higher vs. lower adherences to the MeDi using published protocols. Estimates of cortical thickness for entorhinal cortex (EC), inferior parietal lobe, middle temporal gyrus, orbitofrontal cortex (OFC) and posterior cingulate cortex (PCC) were obtained by use of automated segmentation tools (FreeSurfer). Multivariate general linear models and linear regressions assessed the associations of MeDi with MRI measures. RESULTS: Of the 52 participants, 20 (39%) showed higher MeDi adherence (MeDi+) and 32 (61%) showed lower adherence (MeDi-). Groups were comparable for clinical, neuropsychological measures, presence of a family history of AD (FH), and frequency of Apolipoprotein E (APOE) ε4 genotype. With and without controlling for age and total intracranial volume, MeDi+ subjects showed greater thickness of AD-vulnerable ROIs as compared to MeDi- subjects (Wilk’s Lambda p=0.026). Group differences were most pronounced in OFC (p=0.001), EC (p=0.03) and PCC (p=0.04) of the left hemisphere. Adjusting for gender, education, FH, APOE status, BMI, insulin resistance scores and presence of hypertension did not attenuate the relationship. CONCLUSION: NL individuals showing lower adherence to the MeDi had cortical thinning in the same brain regions as clinical AD patients compared to those showing higher adherence. These data indicate that the MeDi may have a protective effect against tissue loss, and suggest that dietary interventions may play a role in the prevention of AD

Blood pressure decrease correlates with tau pathology and memory decline in hypertensive elderly

In hypertension (HTN), cerebral blood flow regulation limits are changed, and the threshold for blood pressure (BP) at which perfusion is safely maintained is higher. This shift may increase the brain's vulnerability to lower BP in subjects with vascular disease. We investigated whether longitudinal reduction in mean arterial pressure (MAP) was related to changes in cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease in a group of cognitively healthy elderly with and without HTN. The relationships among MAP, memory decline, and hippocampal atrophy were also examined. Seventy-seven subjects (age 63.4 ± 9.4, range 44-86 years; education 16.9 ± 2.1, range 10-22 years; 60% women) were assessed twice, 2 ± 0.5 years apart. At both time points, all subjects underwent full medical and neuropsychological evaluations, lumbar punctures, and magnetic resonance imaging examinations. Twenty-five subjects had HTN. Hyper- and normotensive subjects did not differ in their CSF biomarkers, hippocampal volumes (HipVs), or memory scores at baseline. In the entire study group, the increase in tau phosphorylated at threonine 181 (p-tau(181)) was associated with a decline in verbal episodic memory (β = -0.30, p = 0.01) and HipV reduction (β = -0.27, p = 0.02). However, longitudinal decrease in MAP was related to memory decline (β = 0.50, p = 0.01) and an increase in p-tau(181) (β = -0.50, p = 0.01) only in subjects with HTN. Our findings suggest that the hypertensive group may be sensitive to BP reductions.

Reduced mitochondria cytochrome oxidase activity in adult children of mothers with Alzheimer's disease

Biomarker studies demonstrate inheritance of glucose hypometabolism and increased amyloid-β deposition in adult offspring of mothers, but not fathers, affected by late-onset Alzheimer's disease (LOAD). The underlying genetic mechanisms are unknown. We investigated whether cognitively normal (NL) individuals with a maternal history of LOAD (MH) have reduced platelet mitochondrial cytochrome oxidase activity (COX, electron transport chain complex IV) compared to those with paternal (PH) or negative family history (NH). Thirty-six consecutive NL individuals (age 55 ± 15 y, range 27-71 y, 56% female, CDR = 0, MMSE ≥28, 28% APOE-4 carriers), including 12 NH, 12 PH, and 12 MH, received a blood draw to measure platelet mitochondrial COX activity. Citrate synthase activity (CS) was measured as a reference. Groups were comparable for clinical and neuropsychological measures. We found that after correcting for CS, COX activity was reduced by 29% in MH compared to NH, and by 30% in MH compared to PH (p ≤ 0.006). Results remained significant controlling for age, gender, education, and APOE. No differences were found between PH and NH. COX measures discriminated MH from the other groups with accuracy ≥75%, and relative risk ≥3 (p ≤ 0.005). Among NL with LOAD-parents, only those with MH showed reduced COX activity in platelet mitochondria compared to PH and NH. The association between maternal history of LOAD and systemic COX reductions suggests transmission via mitochondrial DNA, which is exclusively maternally inherited in humans.

Amyloid and metabolic positron emission tomography imaging of cognitively normal adults with Alzheimer's parents

This study examines the relationship between fibrillar beta-amyloid (Aβ) deposition and reduced glucose metabolism, a proxy for neuronal dysfunction, in cognitively normal (NL) individuals with a parent affected by late-onset Alzheimer's disease (AD). Forty-seven 40-80-year-old NL received positron emission tomography (PET) with (11)C-Pittsburgh compound B (PiB) and 18F-fluoro-2-deoxy-d-glucose (FDG). These included 19 NL with a maternal history (MH), 12 NL with a paternal history (PH), and 16 NL with negative family history of AD (NH). Automated regions of interest, statistical parametric mapping, voxel-wise intermodality correlations, and logistic regressions were used to examine cerebral-to-cerebellar PiB and FDG standardized uptake value ratios across groups. The MH group showed higher PiB retention and lower metabolism in AD regions compared with NH and PH, which were negatively correlated in posterior cingulate, frontal, and parieto-temporal regions (Pearson r ≤ -0.57, p ≤ 0.05). No correlations were observed in NH and PH. The combination of Aβ deposition and metabolism yielded accuracy ≥ 69% for MH vs. NH and ≥ 71% for MH vs. PH, with relative risk = 1.9-5.1 (p values < 0.005). NL individuals with AD-affected mothers show co-occurring Aβ increases and hypometabolism in AD-vulnerable regions, suggesting an increased risk for AD.

Alzheimer's disease markers, hypertension, and gray matter damage in normal elderly

It is not well known whether Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers are associated with brain damage in cognitively normal elderly. The combined influence of CSF biomarkers and hypertension (HTN) on the gray matter (GM) is also not well described. One hundred fifteen cognitively healthy subjects (mean age 62.6 ± 9.5%, 62% women) received clinical assessment, a high resolution magnetic resonance imaging (MRI), and a lumbar puncture. The CSF levels of total tau (t-tau), hyperphosphorylated tau (p-tau(231)), amyloid beta (Aβ42/Aβ40), p-tau(231)/Aβ42, and t-tau/Aβ42 were dichotomized as "high" and "low" based on accepted cut off values. Statistical parametric mapping was used to examine MRI scans for regional GM density, studied as a function of the CSF markers, HTN, and combination of both. Global and medial temporal lobe (MTL) GM was also assessed. Voxel based morphometry revealed that higher t-tau was associated with lower GM density in the precunei. Subjects with higher p-tau(231) and p-tau(231)/Aβ42 had less GM in temporal lobes. Low Aβ42/Aβ40 was related to less GM in the thalami, caudate, and midbrain. Subjects with hypertension showed more GM atrophy in the cerebellum, occipital, and frontal regions. Simultaneous presence of elevated CSF AD biomarkers and HTN was associated with more GM atrophy than either marker individually, but no interaction effects were identified. In conclusion, in normal elderly CSF tau markers were associated predominantly with lower GM estimates in structures typically affected early in the AD process. In this presymptomatic stage when no cognitive impairment is present, AD biomarkers and HTN have additive effects on gray matter damage.

Maternal age affects brain metabolism in adult children of mothers affected by Alzheimer's disease

Cognitively normal (NL) individuals with a maternal history of late-onset Alzheimer's disease (MH) show reduced brain glucose metabolism on FDG-PET as compared to those with a paternal history (PH) and those with negative family history (NH) of Alzheimer's disease (AD). This FDG-PET study investigates whether metabolic deficits in NL MH are associated with advancing maternal age at birth. Ninety-six NL individuals with FDG-PET were examined, including 36 MH, 24 PH, and 36 NH. Regional-to-whole brain gray matter standardized FDG uptake value ratios were examined for associations with parental age across groups using automated regions-of-interest and statistical parametric mapping. Groups were comparable for clinical and neuropsychological measures. Brain metabolism in AD-vulnerable regions was lower in MH compared to NH and PH, and negatively correlated with maternal age at birth only in MH. There were no associations between paternal age and metabolism in any group. Evidence for a maternally inherited, maternal age-related mechanism provides further insight on risk factors and genetic transmission in late-onset AD.

Pharmacodynamic (PD) evaluation of LY2181308 in patients with metastatic malignancies

3507

Background: Survivin is an inhibitor of apoptosis and its overexpression in cancer has been associated with poor survival. LY2181308 (LY), a novel modified antisense oligonucleotide is a specific inhibitor of survivin. The safety and PK profile of LY from this first-in-human study was presented at ASCO 2008. We now present the PD data from this trial. Methods: Patients with advanced or metastatic malignancies who had failed previous anti-tumor treatments were enrolled. Three consecutive IV loading doses given over 3 hours were followed by weekly maintenance doses. Pre- and post-dosing biopsies were mandated to test for evidence of modification of the target at doses where a PD effect was expected. Biopsies were taken 48 hours after the last loading dose by CT-guided fine needle biopsy. Tumor tissue was paraffin-embedded for immunohistochemistry (IHC) and survivin gene expression. Given the finite amount of biopsy material, the quantification of survivin protein was prioritized. In addition, at one site, pre- and post-dosing endobronchial sampling was conducted in NSCLC patients, with the aim of quantifying levels of native survivin protein, and assessing changes in cell cycle profile in freshly isolated tumor cells using FACS analysis. Results: Out of the 34 patients enrolled, 22 patients had a pre- and posttreatment biopsy. Results from IHC indicated that survivin expression was reduced in the nucleus and cytoplasm in 11/17 and 5/14 evaluable pairs, respectively. LY was detected in neoplastic and non-neoplastic tumor cells in 5/16 and 15/16 evaluable pairs respectively. Gene expression analysis indicated a reduction in survivin expression by 20% to 50% in 11/15 evaluable pairs. Analysis of the fresh tumor material from endobronchial sampling revealed that 2 out of 3 patients with NSCLC had a near-complete elimination of survivin-positive cells accompanied by an increase in the fraction of cells with a sub-G1 DNA content, consistent with cell death. Conclusions: In this study, we were able to demonstrate the presence of the ASO in tumor tissue and confirm a reduction in survivin protein and gene expression. These findings demonstrate the proof of principle of antitumor activity of LY and provide the rationale for phase II studies.

[Table: see text]

A biomechanical study comparing the compressive forces generated by a conventional 4.5 AO/ASIF cortical lag screw with a differentially pitched cortical compression screw

The aim of this study was to compare the interfragmentary compression generated across a simulated femoral fracture model by a conventional 4.5 mm AO/ASIF cortical lag screw with a differentially pitched cortical compression screw. A 45-degree osteotomy was made in a whole bone composite femoral shaft, this was internally fixed with either a conventional 4.5 mm AO/ASIF cortical lag screw or the differentially pitched cortical screw and the compressive force generated at the fracture site measured on an Instron 8874 Axial/Torsion Servohydraulic Testing System. The mean interfragmentary compression generated by the differentially pitched screw was 81.4% of that generated by the 4.5 mm AO/ASIF cortical lag screw. The 4.5 mm AO/ASIF cortical screw produces a steep rise in compression per turn of the screw. The screw based on the differential pitch design creates a more gradual increase to peak compression. The resistance to torque was greater for the AO screw than for the differential pitch screw. Maximal interfragmentary compression is achieved within 4 180 degrees turns after the head engages the near cortex for the 4.5 mm AO/ASIF screw but required 5 180 degrees turns for the differentially pitched screw. Interfragmentary compression is achievable in cortical bone using differential pitch technology. A differentially pitched screw offers obvious advantages over a conventional screw allowing independent placement of lag screw and neutralisation plate, without needing additional exposure of the fracture site, limiting the insult to local fracture biology. It is proposed as an adjunct to osteosynthesis in long bone fractures.

Single voxel proton magnetic resonance spectroscopy in post-stroke depression

Mood disorders are associated with structural, metabolic and spectroscopic changes in prefrontal regions. In the case of depression associated with stroke, there is little information about the biochemical profile of these regions, as assessed by proton magnetic resonance spectroscopy ((1)H-MRS). In a group of first-ever stroke patients, we studied the association between post-stroke depression and (1)H-MRS measurements in unaffected frontal lobes. Twenty-six patients with a first ischemic stroke located outside the frontal lobes were included in the study. Single voxel proton magnetic resonance spectroscopy ((1)H-MRS) was performed to assess N-acetylaspartate/creatine (NAA)/Cr, glutamate+glutamine (Glx)/Cr, choline (Cho)/Cr and myo-inositol (mI)/Cr ratios. Patients were assessed within the first 10 days after stroke and again four months later. The diagnosis of depression was made on the basis of clinical observation, interview and Hamilton Depression Rating Scale scores. In a group of 26 patients, eight (31%) met criteria for depression at the first assessment, and nine (35%) met criteria for depression at follow-up. Patients with depression in the immediate post-stroke phase had significantly higher Glx/Cr ratios in the contralesional hemisphere than non-depressive patients. No biochemical differences were found between the groups at 4-month follow-up. These findings suggest that post-stroke depression is accompanied by changes in frontal lobe glutamate/glutamine levels, perhaps reflecting abnormalities in glutamatergic transmission in the immediate post-stroke period.

Molecular analysis of polymerase gamma gene and mitochondrial polymorphism in fertile and subfertile men

CAG trinucleotide repeat length in the nuclear polymerase gamma gene (POLgamma) has been shown to be associated with men with reduced fertility. The present study investigated the frequency of CAG repeat length genotypes and three exonuclease motifs of the POLgamma in relation to the frequency of mitochondrial nucleotide substitutions. DNA from semen samples of 93 normozoospermic men and 192 non-normozoospermic men was isolated and the specific regions of the genes were amplified by polymerase chain reactions (PCR) and sequenced to identify mutations. The genotypic frequencies of pooled POLgamma CAG repeat lengths, =10/ not equal 10 heterozygotes and not equal 10/ not equal 10 homozygotes, were significantly different between normozoospermic and non-normozoospermic men (p < 0.05), with non-normozoospermic men having a slightly higher frequency of the =10/=10 genotypes. The allelic frequency for =10 is 0.79 and not equal10 is 0.21 for normozoospermic men and 0.85 and 0.15, respectively, for non-normozoospermic men (p < 0.025). There was no mutation detected in the exonuclease motifs in all the samples tested. Eighty normozoospermic and 124 non-normozoospermic semen samples were analysed for nucleotide substitutions in mitochondrial genes by PCR and sequencing. Heteroplasmic mutations were found in one azoospermic man, four asthenozoospermic men and two normozoospermic men. Only one asthenozoospermic man was heterozygous for the POLgamma genotype. Of the 17 men with non-synonymous nucleotide substitutions, 14 were homozygous for the POLgamma genotype. Non-normozoospermic men had twice as many nucleotide substitutions than normozoospermic men. However, there were no significant differences in the frequencies of nucleotide substitution and POLgamma genotypes in the two groups of men.

Subjective memory complaints in aging are associated with elevated cortisol levels

The origin and clinical significance of subjective memory complaints among middle aged and older individuals is not well understood. Associations with objective memory impairments, personality traits or mood disturbances have been reported. Elevated cortisol levels occur in aging and depression and causal links to cognitive or emotional problems have been suggested. The goal of this study was to investigate the associations between basal and feedback indices of cortisol regulation and subjective memory impairment in a sample of healthy middle aged and older subjects (mean age 61.8 years) with (n=27) and without (n=19) subjective memory complaints. Participants with memory complaints had both higher basal cortisol levels and higher cortisol levels after dexamethasone. There was a significant group by gender interaction for basal cortisol levels, where women without memory complaints showed significantly lower cortisol levels, whereas no such difference was found for the men. All effects were not due to slight differences in depression scores. Differences in personality traits or in stress susceptibility might underlie the present findings. Future studies of memory complaints should take a comprehensive approach including relevant endocrine parameters.

The random blood glucose level, a risk factor for mortality after acute myocardial infarction, in non-diabetic patients

The Correlation between blood glucose level and cardio-vascular events is well established in diabetic patients. In this study, fifty three non diabetic (M:30F:23), patients after acute myocardial infarction were studied for mortality in the following two years, retrospectively. Every patient had random venous glucose estimated on admission. This glucose level was correlated with all cause mortality. At the end of 2 years, 13 patients died and 40 remained alive. There was a significant difference of blood glucose between those who died and remained alive. The difference between the mean blood glucose level is between 0.6 mmol/L and 3.8 mmol/L higher for patients who died (mean = 8.62); compared with those that were still alive (mean = 6.69). This difference was particularly observed in the group of anterior wall infarction. The subgroup analysis also revealed that the difference between the mean blood glucose levels is 9 mmol/L for female patients with heart failure compared with those who did not suffer from heart failure (mean 6.8). The study concludes that, the higher glucose level is associated with increased all cause mortality in the following 2 years of first acute myocardial infarction.

Strain on the human sciatic nerve in vivo during movement of the hip and knee

Injuries to the sciatic nerve are an occasional complication of surgery to the hip and acetabulum, and traction is frequently the causative mechanism. In vitro and animal experiments have shown that increased tensile strain on peripheral nerves, when applied for prolonged periods, impairs nerve function. We have used video-extensometry to measure strain on the human sciatic nerve during total hip replacement (THR). Ten consecutive patients with a mean age of 72 years undergoing primary THR by the posterior approach were recruited, and strains in the sciatic nerve were measured in different combinations of flexion and extension of the hip and knee, before dislocation of the hip. Significant increases (p = 0.02) in strain in the sciatic nerve were observed in flexion of the hip and extension of the knee. The mean increase was 26% (19% to 30%). In animal studies increases of this magnitude have been shown to impair electrophysiological function in peripheral nerves. Our results suggest that excessive flexion of the hip and extension of the knee should be avoided during THR.

High incidence of single nucleotide substitutions in the mitochondrial genome is associated with poor semen parameters in men

Single nucleotide polymorphisms (SNPs) in 7000 bp of the mitochondrial genome, encompassing 15 coding regions from COI to ND5, were characterized by single strand polymorphism analysis and confirmed by DNA sequencing. About 2.4% of normozoospermic men and 8.4% of men with poor semen quality had at least one nucleotide substitution. Most of the substitutions occurred in the third codon and did not change the amino acid. Hydrophobicity plots of the proteins with changes in an amino acid as a result of a nucleotide substitution suggested that they did not affect the function of the protein. The two most common substitutions at nucleotide (nt) 9055 and 11719 had significantly higher frequencies in men with reduced sperm motility. Eleven percent of the men with poor semen parameters and 1.3% of normozoospermic men had a 9055 substitution, 12% of the men with poor semen parameters had a substitution at nt 11719, but none of the normozoospermic men had this substitution. All the patients with these substitutions had reduced sperm motility and/or low sperm count. These SNPs in the mitochondrial genome were in a homoplasmic state. Thus, we propose that possessing these mitochondrial mutations compromises the semen quality of these men.

Effect of stride length on symptoms of exercise-induced muscle damage during a repeated bout of downhill running

The purpose of this study was to assess the effects of changes in stride length on the symptoms of exercise-induced muscle damage (EIMD) during a repeated bout of downhill running in a group of 18 men and women. Muscle tenderness, plasma creatine kinase activity (CK) and maximal voluntary isometric force were measured before and after two downhill runs, with each run separated by 5 weeks. The first downhill run was at the preferred stride frequency (PSF). Participants were then randomly allocated to one of three sex-balanced groups with equal numbers of men and women: overstride (-8% PSF), understride (+8% PSF) and normal stride frequency for the second downhill run. Stride length had no effect (P>0.05) on muscle tenderness, CK or isometric peak force. Increases in muscle tenderness (P<0.001) and CK were lower (P<0.05) following the second downhill run, although there was no difference in the pattern and extent of the strength decrement between the two runs. There were also no differences (P>0.05) in muscle tenderness, CK or the relative strength loss between the men and the women. Results suggest that the symptoms of EIMD are unaffected by gender and small alterations to the normal stride pattern during constant velocity downhill running. The observation that muscle tenderness and CK were reduced following a repeated bout of similar eccentric exercise is consistent with the phenomenon known as the 'repeated bout effect' of muscle damage.

MRI volume of the amygdala: a reliable method allowing separation from the hippocampal formation

Studies of MRI-derived volume of the amygdala have been mostly performed on coronal sections where its boundaries with the hippocampus and the entorhinal cortex are indistinct. To date, all reports of in vivo amygdala volume have consistently overestimated the size of the structure. We have developed a method for the MRI-based in vivo measurement of the amygdala volume which allows a better separation of the amygdala from the adjoining hippocampal formation. In nine normal volunteers we obtained three-dimensional spoiled gradient recalled acquisition, 1.3-mm thick, T1 weighted sagittal MR images and created electronically linked reformatted images in the coronal and axial planes. On the original sagittal and the reformatted axial planes, where it is more readily apparent, we delineated the boundaries between the amygdala and the hippocampus and the amygdala and the hippocampo-amygdala transition area, respectively. We then projected those markings onto the coronal plane, where the other boundaries of the amygdala are more easily seen. Using these markings as a guide and utilizing extra-amygdalar coronal landmarks for the anterior end, we outlined the whole amygdala on the coronal plane and determined its volume. We observed that 45% of the coronal slices that contained amygdala also contained some hippocampus. The amygdala measurement had high test-retest reliability, with an intra-class correlation coefficient (rICC) of 0.99 for the total volume and an rICC of 0.93 for the measurement at the level of the individual slice. The average amygdala volume was 1.05 +/- 0.17 cm3 on the right and 1.14 +/- 0.15 cm3 on the left. Our amygdala volumes are in agreement with those reported in postmortem studies, which provides the reported method with face validity.

Comparison of the effects of topical lignocaine spray applied before or after induction of anaesthesia on the pressor response to direct laryngoscopy and intubation

In an attempt to attenuate the cardiovascular pressor response to laryngoscopy and intubation, 30 patients presenting for routine ophthalmic surgery were studied and were randomly allocated into two groups: group A (n = 15) received direct laryngeal/tracheal lignocaine spray immediately before intubation; and group B (n = 15) received orolaryngeal lignocaine spray before the induction of anaesthesia. In both groups, general anaesthesia was induced with thiopentone 3-5 mg kg-1, followed by atracurium 0.6 mg kg-1 to facilitate tracheal intubation. Laryngoscopy and endotracheal intubation caused a significant increase in heart rate, by 28% in group A and 23% in group B (P < 0.05 in both), and in diastolic blood pressure, by 28% in group A and 24% in group B (P < 0.05 in both). In group A, the systolic blood pressure also increased significantly (by 18%) after intubation, but there was no significant change in group B. In addition, the plasma lignocaine concentrations remained well below the toxic range in both groups. It was concluded that topical lignocaine administration as an orolaryngeal spray before the induction of anaesthesia is effective in reducing but not abolishing the pressor response to laryngoscopy and endotracheal intubation.

Caffeine and schizophrenia

Although the database is small and not completely consistent, it appears that patients with schizophrenia have high caffeine intakes. The reasons are unclear. In nonhumans, caffeine enhances the effects of dopamine, which might be expected to worsen positive symptoms and improve negative symptoms of schizophrenia and worsen tardive dyskinesia. Eliminating caffeine among patients with schizophrenia does not appear to make them better or worse. Acute intake of large amounts of caffeine may increase psychoses and hostility. However, those who chronically use large amounts of caffeine may develop enough tolerance that these adverse effects do not occur, but whether this conjecture is true has not been tested. Interestingly, persons with schizophrenia do not develop anxiety at high doses of caffeine. Although there was initial concern that caffeine might inactivate liquid doses of neuroleptics, the clinical significance of this concern is unclear. On the other hand, caffeine might increase the level of clozapine, and more research in this area is needed.

Evaluation of a protocol to select patients of all ages for cardioversion from atrial fibrillation

OBJECTIVE

to audit the success of a decision protocol to select patients for cardioversion from atrial fibrillation or flutter by recording the success of cardioversion and the maintenance of sinus rhythm over a 2-year period.

DESIGN

retrospective case notes review.

SETTING

a teaching hospital coronary care unit and cardiology department.

PATIENTS

227 consecutive patients were considered for cardioversion from atrial fibrillation or flutter from 1989 to 1992; 128 fulfilled the selection criteria.

MAIN OUTCOME MEASURES

successful cardioversion and maintenance of sinus rhythm after cardioversion.

RESULTS

116 (91%) patients selected by application of the guidelines were successfully cardioverted. The probabilities of maintaining sinus rhythm at 6, 12 and 24 months were 0.92, 0.88 and 0.73 respectively.

CONCLUSION

careful selection of patients in atrial fibrillation identifies a group in whom cardioversion is likely to be safe and successful regardless of age.

Addison's disease and selective IgA deficiency in two coeliac patients

Coeliac disease is associated with selective IgA deficiency and various autoimmune disorders. An association between Addison's disease and coeliac disease has been documented previously in the literature but never heretofore in coeliac patients with selective IgA deficiency. From a coeliac registry of over 700 biopsy-proven coeliac patients, studied closely over a 25-year period at University College Hospital, Galway, we now report the finding of Addison's disease and selective IgA deficiency in two patients with established coeliac disease. Previous reports of Addison's disease in coeliac patients were sporadic, and it was felt that the association between the two conditions was fortuitous. We now believe that coeliac patients, especially those who are selectively deficient in serum IgA, should be followed up with increased vigilance, as the association between IgA-deficient coeliac patients and Addison's disease is greater than can be explained by chance. Furthermore, we suggest that patients with established Addison's disease may have subclinical coeliac disease and should be screened with anti-reticulin or anti-endomyseal antibodies.

Mechanical characteristics of dilated polytetraflouroethylene used for transluminally placed endovascular grafts

This study was conducted to assess the mechanical characteristics of dilated polytetraflouroethylene (PTFE) for use in transluminally placed endovascular grafts (TPEGs). Ten-centimeter lengths of 3- and 4-mm thinwalled PTFE were dilated to 8, 10, 12, and 15 mm diameters (3 mm) and 10-, 14-, 16-, and 20-mm diameters (4 mm), respectively (n = 6 for each size). The dilated PTFE segments were evaluated for leakage, further dilation, structural changes (with electron microscopy), and changes in wall thickness occurring after 24 hours of perfusion at pressures of 300-350 mmHg. Both 3- and 4-mm thinwalled PTFE could be dilated to five times their initial diameter before rupture occurred. Three-millimeter grafts dilated to 12- and 4-mm grafts dilated to 14 mm remained resistant to leakage at perfusion pressures up to 350 mmHg. When 3-mm grafts were dilated to 15 mm, the PTFE leaked saline at a rate of 20.3 +/- 9.3 cc per hour at 300 mmHg. pressure. Four-millimeter grafts dilated to 16- and 20-mm diameters leaked saline at 8.4 +/- 7.8 and 52.8 +/- 22 cc per minute, respectively, at the same pressure. No grafts were found to increase in diameter after 24 hours of pressure perfusion. Electron microscopy revealed that PTFE node size was significantly smaller in dilated grafts than in undilated grafts, but there was no significant change in internodal distance. This data suggests that thinwalled PTFE can be dilated to large diameters and retain sufficient strength to resist supraphysiologic pressures. Long-term studies are needed to determine the late structural integrity of dilated PTFE.