The histological validation of post mortem magnetic resonance imaging-determined hippocampal volume in Alzheimer's disease

For 11 AD cases and four normal elderly controls, post mortem volumes of the hippocampal subdivisions were calculated by using magnetic resonance imaging and histological sections. After at least six weeks of fixation in formalin, brains were examined on a 1.5-T Philips Gyroscan imager producing T1-weighted coronal images with a 3-mm slice thickness. Brains were then processed and embedded in paraffin. Serial coronal sections, 3 mm apart and stained with Cresyl Violet, were used for the planimetry and unbiased estimation of the total numbers of neurons in the hippocampal subdivisions. For all 15 cases, magnetic resonance imaging- and histology-based measurements were performed along the whole rostrocaudal extent of the hippocampal formation and included three subvolumes: (i) the hippocampus (CA1-CA4 and the dentate gyrus); (ii) hippocampus/subiculum; and (iii) hippocampus/parahippocampal gyrus. After controlling for shrinkage, strong correlations were found between magnetic resonance imaging and histological measurements for the hippocampus (r = 0.97, P < 0.001), hippocampus/subiculum (r = 0.95, P < 0.001) and hippocampus/parahippocampal gyrus (r = 0.89, P < 0.001). We also calculated the total number of neurons in the hippocampus and hippocampus/subiculum subvolumes. Strong correlations between the magnetic resonance imaging subvolumes and neuronal counts were found for the hippocampus (r = 0.90, P < 0.001) and the hippocampus/subiculum subvolume (r = 0.84, P < 0.001). We conclude that very accurate volumetric measurements of the whole hippocampal formation can be obtained by using a magnetic resonance imaging protocol. Moreover, the strong correlations between magnetic resonance imaging-based hippocampal volumes and neuronal numbers suggest the anatomical validity of magnetic resonance imaging volume measurements.     

Exercise performance and magnetic resonance imaging-determined thigh muscle volume in children

This study examined the relationships between thigh muscle volume (TMV) and aerobic and anaerobic performance in children. A total of 32 children, 16 boys and 16 girls, aged 9.9 (0.3) years completed a treadmill running test to exhaustion for the determination of peak oxygen uptake (peak V˙O₂) and a Wingate Anaerobic Test (WAnT) for the determination of peak power (PP) and mean power (MP). The volume of the right thigh muscle was determined using magnetic resonance imaging. TMV was not significantly different in boys and girls [2.39 (0.29) l vs 2.18 (0.38) l, P > 0.05]. Peak V˙O₂ and MP were significantly higher in boys than girls (P < 0.01) whether expressed in absolute, mass-related or allometrically scaled terms. Absolute PP was not significantly different in boys and girls but mass-related and allometrically scaled values were higher in boys (P < 0.01). TMV was correlated with absolute peak V˙O₂, PP and MP in both sexes (r = 0.52–0.89, P < 0.01). In boys, mass-related PP was correlated with TMV (r =0.53, P < 0.01), and in girls mass-related peak V˙O₂ was correlated with TMV (r = ?0.61, P < 0.01). However, in neither sex were allometrically scaled peak V˙O₂, PP or MP correlated with TMV (P > 0.05). There were no significant differences between boys and girls in terms of peak V˙O₂, PP or MP when expressed in a ratio to TMV or allometrically scaled TMV. In conclusion, this study has demonstrated that, when body size is appropriately accounted for using allometric scaling, TMV is unrelated to indices of aerobic and anaerobic power in 10-year-old children. Furthermore, there appear to be no qualitative differences in the muscle function of boys and girls in respect of aerobic and anaerobic function.     

Ex vivo lumbar and post mortem ventricular cerebrospinal fluid substance P-immunoreactivity in Alzheimer's disease patients

The concentration of substance P-immunoreactivity (SPIR) in ex vivo lumbar cerebrospinal fluid (CSF) of patients with probable Alzheimer's disease (AD), non-Alzheimer dementias, neurological patients without dementia and control subjects was determined using a sensitive and specific competitive enzyme-immunoassay. There were no significant differences between AD patients and the other groups, but patients with late onset AD (>65 years) showed significantly higher levels of SPIR than patients with early onset (<65 years) and controls. In post mortem ventricular fluid, SPIR levels of all groups were lower compared with the lumbar compartment, but without significant group differences. It is concluded that CSF SPIR may not serve as a diagnostic marker for AD, but possibly could reflect immunological or neuroprotective processes modulated by substance P in late onset AD patients.     

Slowing of electroencephalogram and choline acetyltransferase activity in post mortem frontal cortex in definite Alzheimer's disease.

Twenty-five (96%) of 26 patients with histologically verified moderate to severe Alzheimer's disease had abnormal electroencephalograms. The patients with the slowest (5-6 Hz) dominant occipital rhythms had significantly lower choline acetyltransferase activity in the post mortem frontal cortex than the patients with highest rhythm (8-9 Hz) (analysis of covariance adjusted for the neuropsychological test score). Concentrations of dopamine, noradrenaline or serotonin in the frontal cortex did not differ in the patient groups with the slowest and highest rhythms. Neither did scores of senile plaques or neurofibrillary tangles differ between these groups. In Alzheimer patients, the frequency of the dominant occipital rhythm correlated with the total score of the neuropsychological test (r = 0.58, P less than 0.01) and with the subscales of praxic functions and expressive speech, memory and general reasoning. The results suggest that the cholinergic deficit may contribute to the slowing of the electroencephalogram found in patients with Alzheimer's disease.     

CSF tau markers are correlated with hippocampal volume in Alzheimer's disease

Hippocampal atrophy as assessed by magnetic resonance imaging (MRI) and abnormal cerebrospinal fluid (CSF) biomarkers are supportive features for the diagnosis of Alzheimer's disease (AD) and are assumed to be indirect pathological markers of the disease. In AD patients, antemortem MRI hippocampal volumes (HVs) correlate with the density of neurofibrillary tangles (but not with senile plaques) at autopsy suggesting that HVs may better correlate with CSF tau and hyperphosphorylated tau (P-tau) levels than CSF amyloid beta protein (Aβ)(42) level. Here, we tested this hypothesis in a well-defined AD group. Patients were selected according to the New Research Criteria for AD, including specific episodic memory deficit and CSF AD profile (defined as abnormal ratio of Aβ(42):tau). MRI was performed within 6 months of lumbar puncture. HVs were obtained using automated segmentation software. Thirty-six patients were included. Left HV correlated with CSF tau (R = -0.53) and P-tau (R = -0.56) levels. Mean HVs correlated with the CSF P-tau level (R = -0.52). No correlation was found between any brain measurement and CSF Aβ(42) level. The CSF tau and P-tau levels, but not the CSF Aβ(42) level, correlated with HV, suggesting that CSF tau markers reflect the neuronal loss associated with the physiopathological process of AD.     

Development of the human fetal cerebellum in the second trimester: a post mortem magnetic resonance imaging evaluation

The cerebellum is one of the most important structures in the posterior cranial fossa, but the characterization of its development by magnetic resonance imaging (MRI) is incomplete. We scanned 40 fetuses that had no morphological brain disorder at 14-22 weeks of gestation using 7.0 T MRI. Amira 4.1 software was used to determine morphological parameters of the fetal cerebellum, which included the cerebellar volume (CV), transverse cerebellar diameter (TCD), and the length and width of the vermis. The relationship between these measurements and gestational age (GA) was analysed. We found that the primary fissure was visible at week 14 of gestation. From week 16, the prepyramidal fissure, the secondary fissure and the dentate nucleus could be identified. The posterolateral fissure and the fourth ventricle were recognized at week 17, whereas the tentorium of the cerebellum was visible at week 20. The relationships between GA and CV, TCD, and the width and length of the vermis were described adequately by second-order polynomial regression curves. The ratios between TCD and vermis length and between TCD and vermis width decreased with GA. These results show that 7.0 T MRI can show the trajectory of cerebellar development clearly. They increase our understanding of normal cerebellar development in the fetus, and will facilitate the diagnosis of pathological intrauterine changes in the cerebellum.     

Insulin resistance and hippocampal volume in women at risk for Alzheimer's disease

Insulin resistance (IR) is the main pathological condition underlying vascular disorders, such as diabetes and cardiovascular disease, which are well established risk factors for cognitive decline and Alzheimer disease (AD). Hippocampal atrophy has been associated with cognitive decline, but little is known about the influence of IR on hippocampus integrity in non-diabetic, cognitively intact individuals. Herein, 50 women ages 50-65, current users of hormone therapy, underwent magnetic resonance imaging, cognitive testing, and homeostatic assessment of insulin resistance (HOMA-IR), as part of a longitudinal study examining brain structure and function in postmenopausal women at risk for AD. Results demonstrated a significant negative relationship between HOMA-IR and right and total hippocampal volume, overall cognitive performance, and selective tests of verbal and non-verbal memory. The main effect of HOMA-IR on brain structure and cognition was not altered by the presence of APOE-ε4 allele or by reproductive history, such as duration of endogenous and exogenous estrogen exposure. These results suggest that IR in middle-aged individuals at risk for AD may be biomarker for dementia risk.     

Detection of prodromal Alzheimer's disease via pattern classification of magnetic resonance imaging

We report evidence that computer-based high-dimensional pattern classification of magnetic resonance imaging (MRI) detects patterns of brain structure characterizing mild cognitive impairment (MCI), often a prodromal phase of Alzheimer's disease (AD). Ninety percent diagnostic accuracy was achieved, using cross-validation, for 30 participants in the Baltimore Longitudinal Study of Aging. Retrospective evaluation of serial scans obtained during prior years revealed gradual increases in structural abnormality for the MCI group, often before clinical symptoms, but slower increase for individuals remaining cognitively normal. Detecting complex patterns of brain abnormality in very early stages of cognitive impairment has pivotal importance for the detection and management of AD.     

Functional magnetic resonance imaging as a dynamic candidate biomarker for Alzheimer's disease

During the last two decades, imaging of neural activation has become an invaluable tool for assessing the functional organization of the human brain in vivo. Due to its widespread application in neuroscience, functional neuroimaging has raised the interest of clinical researchers in its possible use as a diagnostic biomarker. A hallmark feature of many neurodegenerative diseases is their chronic non-linear dynamic and highly complex preclinical course. Neurodegenerative diseases unfold over years to decades through clinically silent and asymptomatic stages of early adaptive, compensatory to pathophysiological (i.e. actively neurodegenerative) and decompensatory mechanisms in the brain - phases that are increasingly being considered as critical for primary and secondary preventive and therapeutic measures. Emerging evidence supports the concept of a potentially fully reversible functional phase that may precede the onset of micro- and macrostructural and cognitive decline, a potentially late-stage "neurodegenerative" phase of a primary neurodegenerative disorder. Alzheimer's disease serves as an ideal model to test this hypothesis supported by the neural network model of the healthy and diseased brain. Being highly dynamic in nature, brain activation and neuronal network functional connectivity represent not only candidate diagnostic but also candidate surrogate markers for interventional trials. Potential caveats of functional imaging are critically reviewed with focus on confound variables such as altered neurovascular coupling as well as parameters related to task- and study design.     

Recent developments of functional magnetic resonance imaging research for drug development in Alzheimer's disease

The objective of this review is to evaluate recent advances in functional magnetic resonance imaging (fMRI) research in Alzheimer's disease for the development of therapeutic agents. The basic building block underpinning cognition is a brain network. The measured brain activity serves as an integrator of the various components, from genes to structural integrity, that impact the function of networks underpinning cognition. Specific networks can be interrogated using cognitive paradigms such as a learning task or a working memory task. In addition, recent advances in our understanding of neural networks allow one to investigate the function of a brain network by investigating the inherent coherency of the brain networks that can be measured during resting state. The coherent resting state networks allow testing in cognitively impaired patients that may not be possible with the use of cognitive paradigms. In particular the default mode network (DMN) includes the medial temporal lobe and posterior cingulate, two key regions that support episodic memory function and are impaired in the earliest stages of Alzheimer's disease (AD). By investigating the effects of a prospective drug compound on this network, it could illuminate the specificity of the compound with a network supporting memory function. This could provide valuable information on the methods of action at physiological and behaviourally relevant levels. Utilizing fMRI opens up new areas of research and a new approach for drug development, as it is an integrative tool to investigate entire networks within the brain. The network based approach provides a new independent method from previous ones to translate preclinical knowledge into the clinical domain.     

Recent developments of functional magnetic resonance imaging research for drug development in Alzheimer's disease

The objective of this review is to evaluate recent advances in functional magnetic resonance imaging (fMRI) research in Alzheimer's disease for the development of therapeutic agents. The basic building block underpinning cognition is a brain network. The measured brain activity serves as an integrator of the various components, from genes to structural integrity, that impact the function of networks underpinning cognition. Specific networks can be interrogated using cognitive paradigms such as a learning task or a working memory task. In addition, recent advances in our understanding of neural networks allow one to investigate the function of a brain network by investigating the inherent coherency of the brain networks that can be measured during resting state. The coherent resting state networks allow testing in cognitively impaired patients that may not be possible with the use of cognitive paradigms. In particular the default mode network (DMN) includes the medial temporal lobe and posterior cingulate, two key regions that support episodic memory function and are impaired in the earliest stages of Alzheimer's disease (AD). By investigating the effects of a prospective drug compound on this network, it could illuminate the specificity of the compound with a network supporting memory function. This could provide valuable information on the methods of action at physiological and behaviourally relevant levels. Utilizing fMRI opens up new areas of research and a new approach for drug development, as it is an integrative tool to investigate entire networks within the brain. The network based approach provides a new independent method from previous ones to translate preclinical knowledge into the clinical domain.     

Quantitative autoradiographic analysis of glutamate binding sites in the hippocampal formation in normal and schizophrenic brain post mortem

Using quantitative autoradiography, the anatomical distribution of the binding sites (kainate, N-methyl-D-aspartate and quisqualate) for the excitatory neurotransmitter glutamate has been established in the hippocampal formation from control and schizophrenic brains, post mortem. There is a loss of the kainate subtype particularly in schizophrenic hippocampi mainly from the CA4/CA3 mossy fibre termination zone of the cornu ammonis (CA4 and CA3; control and schizophrenic left hippocampus, respectively, 54.2 and 66.6 pmol/g; 18.3 and 17.9 pmol/g), as well as bilateral losses in the dentate gyrus (left 14.2 pmol/g and right 28.0 pmol/g; left 9.5 pmol/g and right 7.9 pmol/g, control and schizophrenic, respectively) and parahippocampal gyrus (left 50.8 pmol/g and right 41.7 pmol/g, left 27.7 pmol/g and right 25.3 pmol/g, control and schizophrenic, respectively). There is complete preservation of N-methy-D-aspartate sites in schizophrenic hippocampi, and a marginally significant loss of the quisqualate binding site in CA4/CA3 regions (left 249 fmol/g and right 306 fmol/g, left 157 fmol/g and right 148 fmol/g, control and schizophrenic, respectively). These findings reflect the possible importance of glutamate in the pathophysiology of schizophrenia and represent novel targets for therapeutic manipulation in schizophrenia.     

Increased hippocampal quinone reductase 2 in Alzheimer's disease

Quinone reductase 2 (QR2), a detoxifying cytosolic flavoenzyme, is thought to play an important role in the acquisition and loss of memory [3]. We determined the amount of QR2 in the hippocampus, amygdala, and superior frontal gyrus of Alzheimer's disease (AD) patients with dementia by using western blot analysis. The level of QR2 was significantly higher in the hippocampus of AD patients than in that of the control subjects. The relation between QR2 and AD has not yet been determined; however, our results suggest that the increase in hippocampal QR2 might be a cause of AD or might promote the progression of AD by causing an increase in the toxic quinone levels and consequent loss of cognitive function.     

A meta-analysis of hippocampal atrophy rates in Alzheimer's disease

Hippocampal atrophy rates are useful in both diagnosing and tracking Alzheimer's disease (AD). However, cohorts and methods used to determine such rates are heterogeneous, leading to differences in reported annualised rates. We performed a meta-analysis of hippocampal atrophy rates in AD patients and matched controls from studies reported in the peer-reviewed literature. Studies reporting longitudinal volume change in hippocampi in AD subjects together with controls were systematically identified and appraised. All authors were contacted either to confirm the results or to provide missing data. Meta-analysis and meta-regression were then performed on this data. Nine studies were included from seven centres, with data from a total of 595 AD and 212 matched controls. Mean (95% CIs) annualised hippocampal atrophy rates were found to be 4.66% (95% CI 3.92, 5.40) for AD subjects and 1.41% (0.52, 2.30) for controls. The difference between AD and control subject in this rate was 3.33% (1.73, 4.94).     

Curcumin-conjugated magnetic nanoparticles for detecting amyloid plaques in Alzheimer's disease mice using magnetic resonance imaging (MRI)

Diagnosis of Alzheimer's disease (AD) can be performed with the assistance of amyloid imaging. The current method relies on positron emission tomography (PET), which is expensive and exposes people to radiation, undesirable features for a population screening method. Magnetic resonance imaging (MRI) is cheaper and is not radioactive. Our approach uses magnetic nanoparticles (MNPs) made of superparamagnetic iron oxide (SPIO) conjugated with curcumin, a natural compound that specifically binds to amyloid plaques. Coating of curcumin-conjugated MNPs with polyethylene glycol-polylactic acid block copolymer and polyvinylpyrrolidone by antisolvent precipitation in a multi-inlet vortex mixer produces stable and biocompatible curcumin magnetic nanoparticles (Cur-MNPs) with mean diameter <100 nm. These nanoparticles were visualized by transmission electron microscopy and atomic force microscopy, and their structure and chemistry were further characterized by X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, and Fourier transform infrared spectroscopy. Cur-MNPs exhibited no cytotoxicity in either Madin–Darby canine kidney (MDCK) or differentiated human neuroblastoma cells (SH-SY5Y). The P_app of Cur-MNPs was 1.03 × 10⁻⁶ cm/s in an in vitro blood–brain barrier (BBB) model. Amyloid plaques could be visualized in ex vivo T2*-weighted magnetic resonance imaging (MRI) of Tg2576 mouse brains after injection of Cur–MNPs, and no plaques could be found in non-transgenic mice. Immunohistochemical examination of the mouse brains revealed that Cur-MNPs were co-localized with amyloid plaques. Thus, Cur–MNPs have the potential for non-invasive diagnosis of AD using MRI.     

Autoradiography of receptor-activated G-proteins in post mortem human brain

The agonist-stimulated guanosine 5'-(gamma-[(35)S]thio)triphosphate binding assay was used to anatomically localize receptor-activated G-proteins by autoradiography in post mortem human brain. The optimal conditions for guanosine 5'-(gamma-[(35)S]thio)triphosphate binding to human brain sections were established in post mortem samples of the prefrontal cortex, hippocampus, basal ganglia, brainstem and cerebellar cortex. An excess of GDP (2mM) was required to decrease basal activity and obtain effective stimulation by specific agonists. guanosine 5'-(gamma-[(35)S]Thio)triphosphate binding was increased after stimulation with specific agonists of different G-protein-coupled receptors. They include cannabinoid (WIN55212-2), mu-opioid ([D-Ala(2),N-Me-Phe(4), Gly(5)-ol]enkephalin), serotonin-1A [(+/-)-8-hydroxy-2-(di-n-propylamino)tetralin] and serotonin-1B/1D (sumatriptan), cholinergic muscarinic receptors (carbachol) and alpha(2)-adrenoceptors (UK14304). Such stimulation reached 1458%, 440%, 188%, 219%, 61% and 339%, respectively, over the basal levels. In tissue sections, the use of the above-mentioned agonists (10(-4)M) showed patterns of anatomical distribution similar to those already described by receptor autoradiography, with high densities over the hippocampus (serotonin-1A receptors), cortex (alpha(2)-adrenoceptors) and striatum (mu-opioid receptors). The highest binding levels were reached with the cannabinoid receptor agonist in most of the analysed brain regions. Carbachol produced only moderate stimulation of those same regions. The blockage of agonist-stimulated guanosine 5'-(gamma-[(35)S]thio)triphosphate binding by selective antagonists verified that the effect was receptor mediated.This technique provides a method to identify modifications of the receptor-mediated activation of G-proteins in post mortem human brain with anatomical resolution. It also provides valuable information on the level of drug efficacy in the human species.     

Relationship between hippocampal volume and CA1 neuron loss in brains of humans with and without Alzheimer's disease

Hippocampal volumetry has been proposed to aid in the early diagnosis of Alzheimer's disease (AD) and to monitor progression of the disease. While this is believed to be as a result of hippocampal neuron loss, this association has not been firmly established and loss of other tissue elements may be responsible for the observed atrophy. We investigated the relationship between neuron loss and hippocampal volume in 11 patients with autopsy-confirmed AD and 11 non-demented age-matched controls. Strong correlations were found between neuron number and both hippocampal volume and brain volume demonstrating that volume and neuron content are related in normal subjects and that the relationship is maintained in AD. In AD, neuron number and volume measures significantly decline with increasing disease duration. These findings support the suggestion that hippocampal atrophy in AD is as a result of neuron loss and confirm the usefulness of volumetry as an indirect measure of neurodegeneration in this disease.     

Plasticity in hippocampal excitatory amino acid receptors in Alzheimer's disease

Entorhinal cell loss occurs in the course of Alzheimer's disease. In rodents, entorhinal lesions result in axon sprouting in the hippocampus. Quantitative autoradiography was used to examine the density and distribution of N-methyl-D-aspartate (NMDA) and kainic acid (KA) receptors in human hippocampus obtained post-mortem from Alzheimer's disease patients and from age-matched controls. In Alzheimer's disease, there was an expanded distribution of the KA receptor field in the dentate gyrus, indicative of sprouting of the commissural and associational fibers. This regenerative response is thought to facilitate transmission, but in doing so it may also enhance vulnerability to excitotoxic mediated neuronal damage. No significant change was observed in the density or distribution of NMDA receptors. The distribution of these receptors does, however, correlate with the predilection for neurofibrillary tangles and neuritic plaques in hippocampal subfields.     

Frequency of glove puncture in the post mortem room.

The post mortem room is a potential source of danger from contamination caused by glove punctures. The objective of this study was to assess the incidence of hand injury and hand contamination during post mortem examinations. A prospective study of injury and glove puncture rate was conducted during post mortem examinations performed in 1990 on adults in Northwick Park Hospital mortuary. Four pathologists and two assistants performed a total of 44 post mortem examinations on adults. All participants completed a questionnaire after each examination, recording the total number of gloves used and the number of hand injuries and glove perforations sustained. Just over 8.3% of gloves were punctured; 31.8% of these punctures went unnoticed. Evisceration was the procedure most likely to result in hand contamination. The study highlights a significant risk which could be reduced by more care, frequent glove changes, and hand washing during post mortem examinations. In particular, gloves should be changed and hand washed when evisceration has been completed.