Alzheimer's disease biomarkers in Black and non-Hispanic White cohorts: A contextualized review of the evidence

Black Americans are disproportionately affected by dementia. To expand our understanding of mechanisms of this disparity, we look to Alzheimer's disease (AD) biomarkers. In this review, we summarize current data, comparing the few studies presenting these findings. Further, we contextualize the data using two influential frameworks: the National Institute on Aging-Alzheimer's Association (NIA-AA) Research Framework and NIA's Health Disparities Research Framework. The NIA-AA Research Framework provides a biological definition of AD that can be measured in vivo. However, current cut-points for determining pathological versus non-pathological status were developed using predominantly White cohorts-a serious limitation. The NIA's Health Disparities Research Framework is used to contextualize findings from studies identifying racial differences in biomarker levels, because studying biomakers in isolation cannot explain or reduce inequities. We offer recommendations to expand study beyond initial reports of racial differences. Specifically, life course experiences associated with racialization and commonly used study enrollment practices may better account for observations than exclusively biological explanations.

Stressful Life Events and Racial Disparities in Cognition Among Middle-Aged and Older Adults

BACKGROUND

It is well-documented that African Americans have elevated risk for cognitive impairment and dementia in late life, but reasons for the racial disparities remain unknown. Stress processes have been linked to premature age-related morbidity, including Alzheimer's and related dementias (ADRD), and plausibly contribute to social disparities in cognitive aging.

OBJECTIVE

We examined the relationship between stressful life events and cognitive decline among African American and White participants enrolled in the Wisconsin Registry for Alzheimer's Prevention (WRAP).

METHODS

Linear mixed models including demographic, literacy, and health-related covariates were used to estimate (1) relationships between a life event index score and decline in cognitive test performance in two domains of executive function (Speed & Flexibility, Working Memory) and one domain of episodic memory (Verbal Learning & Memory) among 1,241 WRAP enrollees, stratified by race, and (2) contributions of stressful life events to racial differences in cognition within the full sample.

RESULTS

African Americans (N = 50) reported more stressful life events than Whites (N = 1,191). Higher stress scores associated with poorer Speed & Flexibility performance in both groups, though not with declines across time, and partially explained racial differentials in this domain. Among African Americans only, stressor exposure also associated with age-related decline in Verbal Learning & Memory. Stressor-cognition relationships were independent of literacy and health-related variables.

CONCLUSIONS

Greater lifetime stress predicted poorer later-life cognition, and, in a small sample of African Americans, faster declines in a key domain of episodic memory. These preliminary findings suggest that future work in large minority aging cohorts should explore stress as an important source of modifiable, socially-rooted risk for impairment and ADRD in African Americans, who are disproportionately exposed to adverse experiences across the life course.

Association between enrollment factors and incident cognitive impairment in Blacks and Whites: Data from the Alzheimer's Disease Center

INTRODUCTION

We examined the influence of enrollment factors demonstrated to differ by race on incident mild cognitive impairment and dementia using Alzheimer's Disease Center data.

METHODS

Differences in rates of incident impairment between non-Latino Whites and Blacks (n = 12,242) were examined with age-at-progression survival models. Models included race, sex, education, source of recruitment, health factors, and family history of dementia.

RESULTS

No significant race differences in progression were observed in cognitively unimpaired participants. In those with mild cognitive impairment at baseline, Whites evidenced greater risk for progression than Blacks. Enrollment factors, for example, referral source, were significantly related to progression.

DISCUSSION

The finding that Blacks demonstrated lower rate of progression than Whites is contrary to the extant literature. Nested-regression analyses suggested that selection-related factors, differing by race, may account for these findings and influence our ability to accurately estimate risk for progression. It is potentially problematic to make racial comparisons using Alzheimer's Disease Center data sets.

Flavin Binding Allosteric Aptamer with Noncovalent Labeling for miR Sensing

Modular allosteric aptamers with discrete recognition and signaling regions provide a facile method of carrying out label-free detection by forgoing complex target labeling requirements. Herein, we describe the design and function of an aptamer scaffold capable of forming a hairpin loop in the presence of FAD (the signaling trigger). The aptamer includes a recognition region for the microRNA (miR) Let-7i. Upon selective miR hybridization, the aptamer undergoes a conformational shift to release FAD and thus produce a measurable response. As a result, the described method can sensitively and selectively detect miR Let-7i with a wide linear range of 0.1 pM to 1 μM and a detection limit of 150 fM. Additionally, this strategy was able to selectively discriminate between sequences with 1- and 2-nucleotide (nt) differences.

Quantitative [18F]Fluorodopa/PET and Histology of Fetal Mesencephalic Dopaminergic Grafts to the Striatum of MPTP-Poisoned Minipigs

The functional restoration of the dopamine innervation of striatum in MPTP-poisoned Göttingen minipigs was assessed for 6 months following grafting of fetal pig mesencephalic neurons. Pigs were assigned to a normal control group and a MPTP-poisoned group, members of which received no further treatment, or which received bilateral grafts to the striatum of tissue blocks harvested from E28 fetal pig mesencephalon with and without immunosuppressive treatment after grafting, or with additional co-grafting with immortalized rat neural cells transfected to produce GDNF. In the baseline condition, and again at 3 and 6 months postsurgery, all animals were subjected to quantitative [18F]fluorodopa PET scans and testing for motor impairment. At the end of 6 months, tyrosine hydroxylase (TH)-containing neurons were counted in the grafts by stereological methods. The MPTP poisoning persistently reduced the magnitude of k3D, the relative activity of DOPA decarboxylase in striatum, by 60%. Grafting restored the rate of [18F]fluorodopa decarboxylation to the normal range, and normalized the scores in motor function. The biochemical and functional recovery was associated with survival of approximately 100,000 TH-positive graft neurons in each hemisphere. Immunosuppression did not impart a greater recovery of [18F]fluorodopa uptake, nor were the number of TH-positive graft neurons or the volumes of the grafts increased in the immunosuppressed group. Contrary to expectation, co-grafting of transfected GDNF-expressing HiB5 cells, a rat-derived neural cell line, tended to impair the survival of the grafts with the lowest values for graft volumes, TH-positive cell numbers, behavioral scores, and relative DOPA decarboxylase activity. From the results we conclude that pig ventral mesencephalic allografts can restore functional dopamine innervation in adult MPTP-lesioned minipigs.

A clinical system for three-dimensional extended-field-of-view ultrasound

OBJECTIVE

This work is concerned with the creation of three-dimensional (3D) extended-field-of-view ultrasound from a set of volumes acquired using a mechanically swept 3D probe. 3D volumes of ultrasound data can be registered by attaching a position sensor to the probe; this can be an inconvenience in a clinical setting. A position sensor can also cause some misalignment due to patient movement and respiratory motion. We propose a combination of three-degrees-of-freedom image registration and an unobtrusively integrated inertial sensor for measuring orientation. The aim of this research is to produce a reliable and portable ultrasound system that is able to register 3D volumes quickly, making it suitable for clinical use.

METHOD

As part of a feasibility study we recruited 28 pregnant females attending for routine obstetric scans to undergo 3D extended-field-of-view ultrasound. A total of 49 data sets were recorded. Each registered data set was assessed for correct alignment of each volume by two independent observers.

RESULTS

In 77-83% of the data sets more than four consecutive volumes registered. The successful registration relies on good overlap between volumes and is adversely affected by advancing gestational age and foetal movement.

CONCLUSION

The development of reliable 3D extended-field-of-view ultrasound may help ultrasound practitioners to demonstrate the anatomical relation of pathology and provide a convenient way to store data.

The effect of transcatheter injections on cell viability and cytokine release of mononuclear cells

BACKGROUND AND PURPOSE

Several studies suggest that various types of cellular therapies enhance recovery after stroke in animal models. IA-based delivery of cells to the brain is under investigation for stroke, but it is unknown whether cells are injured as a result of being injected through a catheter or exposed to iodinated contrast medium or solutions containing heparin.

MATERIALS AND METHODS

We assessed the effect of catheterization with the Excelsior SL-10 catheter or exposure to heparin or iodine contrast on human bone marrow MNCs. Viability and cell injury were assessed by trypan blue exclusion, caspase-3 activity, and lipid peroxidation. Cellular function of MNCs was assessed by their production and release of VEGF, IL-10, and IGF-1.

RESULTS

Flow rates of 10 million cells from 0.5 to 2 mL/min did not alter MNC viability; however, 5 mL/min of MNCs did reduce viability by 19%. Iodine and low-dose heparin exposure did not affect cell viability; however, high-dose heparin was cytotoxic. Catheter delivery at 2 mL/min did not affect levels of VEGF, IL-10, or IGF-1.

CONCLUSIONS

MNCs do not appear to be damaged by heparin, iodine contrast, and the Excelsior SL-10 catheter at flow rates up to 2 mL/min. However, higher flow rates did reduce viability, and high-dose heparin did cause cell death.

Transplantation of ex vivo expanded cord blood cells using the copper chelator tetraethylenepentamine: a phase I/II clinical trial

The copper chelator tetraethylenepentamine (TEPA; StemEx) was shown to attenuate the differentiation of ex vivo cultured hematopoietic cells resulting in preferential expansion of early progenitors. A phase I/II trial was performed to test the feasibility and safety of transplantation of CD133+ cord blood (CB) hematopoietic progenitors cultured in media containing stem cell factor, FLT-3 ligand, interleukin-6, thrombopoietin and TEPA. Ten patients with advanced hematological malignancies were transplanted with a CB unit originally frozen in two fractions. The smaller fraction was cultured ex vivo for 21 days and transplanted 24 h after infusion of the larger unmanipulated fraction. All but two units contained <2 x 10(7) total nucleated cells (TNCs) per kilogram pre-expansion. All donor-recipient pairs were mismatched for one or two HLA loci. Nine patients were beyond first remission; median age and weight were 21 years and 68.5 kg. The average TNCs fold expansion was 219 (range, 2-620). Mean increase of CD34+ cell count was 6 (over the CD34+ cell content in the entire unit). Despite the low TNCs per kilogram infused (median=1.8 x 10(7)/kg), nine patients engrafted. Median time to neutrophil and platelet engraftment was 30 (range, 16-46) and 48 (range, 35-105) days. There were no cases of grades 3-4 acute graft-versus-host disease (GVHD) and 100-day survival was 90%. This strategy is feasible.

Effect of hormonal growth promotants on palatability and carcass traits of various muscles from steer and heifer carcasses from a Bos indicus - Bos taurus composite cross

The effect of several different hormonal growth promotant (HGP) implant strategies on the palatability and carcass traits of different muscles in beef carcasses was investigated using samples from heifer and steer carcasses from a Bos indicus composite breed. In experiment 1, there were seven different implant strategies evaluated in heifers that were given different combinations of up to three implants (implanted at weaning, during backgrounding and at feedlot entry). A total of 112 heifers were slaughtered and 11 muscles or portions were collected from both sides [Mm. adductor femoris, gracilus, semimembranosus, longissimus dorsi lumborum, triceps brachii caput longum, semispinalis capitis, serratus ventralis cervicis, spinalis dorsi, biceps femoris (syn. gluteobiceps), tensor fasciae latae, gluteus medius (both the ‘D’ and the ‘eye’ portions) rectus femoris, vastus intermedius, vastus lateralis and vastus medialis]. These muscles were used to prepare a total of 1030 sensory samples which were aged for either 7 or 21 days and frozen. Thawed samples were cooked using different cooking methods (grill, roast and stir frying) before being evaluated by a consumer taste panel that scored samples for tenderness, juiciness, like flavour and overall liking. Experiment 2 used the steer portion from the same calving, which were treated to a similar array of HGP strategies, except that they were given up to four implants between weaning and slaughter at ~3 years of age. In experiment 2, there was a total of 12 different HGP implant strategies tested. At boning, three muscles (Mm. psoas major, longisimuss dorsi thoracis and lumborum portions) were collected from each of 79 carcasses with a total of 237 steak samples that consumers tested as grilled steaks. For both experiments, the mean of the HGP implant strategies resulted in increased ossification scores (P < 0.05) and decreased marbling scores (P < 0.05) compared with the controls, with the effect on ossification being much larger in the older steer groups. In both experiments, the different HGP strategies decreased (P < 0.05) all sensory scores compared with the controls, for all cooking method and muscle combinations. In experiment 1, there was no interaction between the mean HGP effect and muscle (P > 0.05), and aging rates differed among the muscles (P < 0.05). In experiment 2, there was a significant (P < 0.05) muscle × HGP treatment interaction, with a decrease in tenderness score due to HGP implant strategies in the M. longisimuss thoracis and lumborum portions, compared with no significant effect in the M. psoas major. For both experiments, there were no significant differences among the different implantation strategies on sensory scores (P > 0.05).

Development of a commercial system to apply the Meat Standards Australia grading model to optimise the return on eating quality in a beef supply chain

A major trial was conducted to develop, test and demonstrate the application of Meat Standards Australia (MSA) research findings in a beef retailing environment. A new concept retail store was established whereby a mix of raw beef products and pre-cooked meals were merchandised under an eating quality grade defined by MSA palatability scores. Products were presented fully prepared within cooking method with pricing based on the predicted cooked results. Large price differentials were established between the three grades offered, with 5-star product priced at more than double the 3-star product. The principle of pricing being directly related to eating quality was extended from the retail store sales to fabrication and the purchase of source cattle from producers. This encouraged considerable innovation to optimise eating quality and returns, demonstrating the potential for truly transparent value-based pricing systems to achieve change. Novel systems were developed to break down and fabricate the carcass into ‘retail-ready’ product with extensive software development to trace the eating quality, value and location of individual cuts and products. Detailed feedback provided the producer with an accurate measure of value and sufficient data to evaluate possible alternative production strategies. Results at each level of the supply chain were encouraging with compound annual growth in sales exceeding 12% at retail level and continued innovation through fabrication and on-farm areas combining to improve eating quality and financial outcomes. It was demonstrated that the consumer focus delivered by MSA grades could be applied at a commercial level providing an opportunity to reposition beef as a contemporary consumer product and to implement a value-based system across all sectors.

Evolution of the Meat Standards Australia (MSA) beef grading system

The Australian Beef Industry identified variable eating quality as a major contributor to declining beef consumption in the early 1990s and committed research funding to address the problem. The major issue was the ability to predict the eating quality of cooked beef before consumption. The Meat Standards Australia (MSA) program developed a consumer testing protocol, which led to MSA grading standards being defined by consumer score outcomes. Traditional carcass grading parameters proved to be of little value in predicting consumer outcomes. Instead a broader combination of factors forms the basis of an interactive prediction model that performs well. The grading model has evolved from a fixed parameter ‘Pathway’ approach, to a computer model that predicts consumer scores for 135 ‘cut by cooking method’ combinations for each graded carcass. The body of research work conducted in evaluating critical control points and in developing the model predictions and interactions has involved several Australian research groups with strong support and involvement from the industry.

Consumer assessment of eating quality - development of protocols for Meat Standards Australia (MSA) testing

Meat Standards Australia sought a consistent measure of the beef eating experience to the consumer. Rather than objective measurements or trained panel sensory assessment, it was decided to proceed with direct consumer assessment. Consumer-based assessment has much greater variation, but it has the decided advantage of validity. This paper summarises the path taken to obtain consistent consumer assessment. What meat samples to present to consumers? What responses to ask for? What to do with these responses when they were obtained? The answers to these questions have led to the MQ4 measure of consumer assessment of meat eating quality, which now forms the basis of the MSA predictive model.

Terminology and labeling of cellular products-2: Implementation plan

The publication of new standards for terminology and labeling marks an important step in ensuring consistency and traceability of cellular therapies at the global level. However, it is only with the widespread implementation of the standard that the benefits can be truly realized. This paper provides guidance on the practical aspects of adopting these new standards for organizations with differing current levels of computerization. It discusses project management, equipment, licensing, and validation topics.

Terminology and labeling of cellular products: 1. Standards

The International Cellular Therapy Coding and Labeling Advisory Group was established to address the growing need for standardization of terminology and labeling for cellular therapy products as a result of increasing international transfer of these products. This paper presents new standards for terminology and labeling. These standards have been developed through a consultative process and are supported by key professional and accreditation bodies. By using these standards, together with the unique donation identification numbers and international product reference tables provided by the International Society of Blood Transfusion (ISBT) 128 Standard, consistency and traceability can be assured at the global level. A companion paper provides guidance on the implementation of the ISBT 128 system.

Using membrane stress to our advantage

The nature of the bilayer motif coupled with the ability of lipids and proteins to diffuse freely through this structure is crucial to the viability of cells and their ability to compartmentalize domains contained therein. It seems surprising to find then that biological as well as model membranes exist in a dynamic state of mechanical stress. The stresses within such membranes are surprisingly large, typically reaching up to 50 atm (1 atm=101.325 kPa) at the core of the membrane and vary as a function of depth. The uneven distribution of lateral pressures within monolayer leaflets causes them to bend away from or towards the water interface. This can result in the formation of complex, self-assembled mesophases, many of which occur in vivo. Our knowledge of the principles underlying membrane mechanics has reached the point where we are now able to manipulate them and create nano-structures with reasonable predictability. In addition, they can be used both to explain and control the partitioning of amphipathic proteins on to membranes. The dependence of the dynamics of membrane-bound proteins and the chemical reactivity of amphipathic drug molecules on membrane stresses suggests that Nature itself takes advantage of this. Understanding and manipulating these internal forces will be a key element in creating self-assembled, biocompatible, nanoscale cell-like systems.

Processing and visualizing three-dimensional ultrasound data

This paper describes techniques for the visualization and processing of three-dimensional (3D) ultrasound data. The nature of such data demands specialized algorithms, which differ from those employed for other medical imaging modalities. In this paper, the emphasis is placed on generic processing techniques, which are relevant across a wide range of 3D ultrasound application domains.

Development of a sensory protocol for testing palatability of sheep meats

A total of 108 grill and 108 roast samples were prepared from lamb (n = 10) and mutton (n = 8) carcasses for sensory testing using a consumer taste panel. Grill and roast samples were prepared from the left and right sides of the carcass, respectively, using longissimus, biceps femoris, gluteus medius, serratus ventralis and semimembranosus. Due to size constraints, muscle from both sides was used to form grill samples for the vastus lateralis, and roast samples from the triceps brachii. Grill and roast samples were sensory tested using 360 untrained consumers. Each consumer was given a total of 6 experimental samples and each sample was tested by 10 different consumers. Sensory scores for tenderness, juiciness, like flavour and overall liking from both the grilled and roasted samples were highly correlated (P<0.05). For grilling, the different muscles were correlated for tenderness and overall liking scores (P<0.05), with the exception of the semimembranosus (P>0.05). In contrast, juiciness and like flavour scores were poorly correlated between grilled muscles. For the roasted samples, sensory scores were generally uncorrelated between muscles. The statistical significance of the age category and muscle effects was greater in grill samples, but stimulation effects were of similar significance using either cooking method. It was proposed that roasting reduced treatment effects that affected sensory via differences in connective tissue toughness, due to gelatinisation of connective tissue during cooking. For testing production and processing effects on palatability, grilling was more sensitive for detecting treatment effects, than roasting.

Effect of rolipram on muscarinic acetylcholine receptor binding in the intact mouse brain

The effect of rolipram, a selective inhibitor of phosphodiesterase type 4 (PDE(4)) and elevating cyclic AMP (cAMP), on in vivo and in vitro (3)H-N-methylpiperidyl benzilate ((3)H-NMPB) binding to muscarinic acetylcholine receptors in the mouse brain was examined. Rolipram significantly decreased in vivo (3)H-NMPB binding in the cerebral cortex, hippocampus and striatum, whereas in vitro (3)H-NMPB binding in these regions was not altered. Saturation experiments on in vivo binding in conjunction with the kinetic analysis revealed that the apparent association rate constant (k(on)) of (3)H-NMPB binding in vivo was significantly decreased by rolipram. A similar decrease in the apparent association rate constant (k(on)) by rolipram was reported for dopamine D(1) and D(2) receptor binding in vivo. These results indicate that rolipram plays an important role in the global modulation of apparent rates of ligand-receptor interactions in the intact brain.

Shame, depressive symptoms and eating, weight and shape concerns in a non-clinical sample

Shame has been shown to be related both to symptoms of depression and eating pathology. However, the independence of this relationship has not yet been established. The purpose of the present study was to determine whether the relationship between shame and eating disorder symptoms was independent of the relationships of these variables with depression. Seventy non-clinical female participants completed measures of eating disorder-related concerns using the Eating Disorder Examination-Questionnaire version (EDE-Q), depressive symptoms using the Beck Depression Inventory (BDI-II) and two measures of shame, the Other As Shamer Scale (QAS) and the Test of Self-Conscious Affect (TOSCA). Despite a strong association between BDI-II and EDE-Q scores and a moderate relationship between the shame measures, the two measures of shame showed some specificity in their relationships with symptom measures. The OAS was independently related to levels of BDI-II scores while the TOSCA was independently related to scores on the EDE-Q. There are a number of differences between the two measures of shame used in this study. The fact that each was differentially related to eating concerns and depressive symptoms may give clues as to which aspects of shame are important in each of the two types of pathology.

Effects of rolipram on in vivo dopamine receptor binding

In order to clarify whether changes in brain concentrations of the second messenger cyclic AMP (cAMP) affect in vivo receptor binding in the brain, the effects of rolipram, a selective inhibitor of phosphodiesterase type 4 (PDE(4)), on dopamine receptor binding in the mouse brain were studied. Rolipram significantly decreased in vivo (3)H-SCH 23390 (dopamine D(1) selective radioligand) binding in the mouse striatum in a dose-dependent manner. In vivo saturation experiments together with the kinetic analysis of (3)H-SCH 23390 binding revealed that the apparent association rate constant (k(on)) for (3)H-SCH 23390 binding rather than the maximum number of binding sites available (B(max)) was decreased by rolipram. (3)H-N-methylspiperone (NMSP, dopamine D(2) selective radioligand) binding in the mouse striatum was also decreased by rolipram whereas no significant changes in (3)H-raclopride (dopamine D(2) selective radioligand) binding were observed. As (3)H-raclopride binding has been reported to be much more sensitive than (3)H-NMSP binding to competition by endogenous dopamine, the decreases in (3)H-SCH 23390 and (3)H-NMSP binding cannot be attributed to competitive inhibition by endogenous dopamine. These results indicate that changes in second messenger cAMP concentrations may affect the apparent bimolecular association rate constant (k(on)) of dopamine receptor binding in intact brain. This may be mediated by changes in the receptor micro-environment and altered actual free ligand concentration surrounding the receptors.

Different sensitivities to competitive inhibition of benzodiazepine receptor binding of 11C-iomazenil and 11C-flumazenil in rhesus monkey brain

The in vivo binding kinetics of 11C-iomazenil were compared with those of 11C-flumazenil binding in rhesus monkey brain. The monkey was anesthetized with ketamine and intravenously injected with either 11C-iomazenil or 11C-flumazenil in combination with the coadministration of different doses of non-radioactive flumazenil (0, 5 and 20 microg/kg). The regional distribution of 11C-iomazenil in the brain was similar to that of 11C-flumazenil, but the sensitivity of 11C-iomazenil binding to competitive inhibition by non-radioactive flumazenil was much less than that of 11C-flumazenil binding. A significant reduction in 11C-flumazenil binding in the cerebral cortex was observed with 20 microg/kg of flumazenil, whereas a relatively smaller inhibition of 11C-iomazenil binding in the same region was observed with the same dose of flumazenil. These results suggest that 11C-flumazenil may be a superior radiotracer for estimating benzodiazepine receptor occupancy in the intact brain.

3D ultrasound measurement of large organ volume

Freehand 3D ultrasound is particularly appropriate for the measurement of organ volumes. For small organs, which can be fully examined with a single sweep of the ultrasound probe, the results are known to be much more accurate than those using conventional 2D ultrasound. However, large or complex shaped organs are difficult to quantify in this manner because multiple sweeps are required to cover the entire organ. Typically, there are significant registration errors between the various sweeps, which generate artifacts in an interpolated voxel array, making segmentation of the organ very difficult. This paper describes how sequential freehand 3D ultrasound, which does not employ an interpolated voxel array, can be used to measure the volume of large organs. Partial organ cross-sections can be segmented in the original B-scans, and then combined, without the need for image-based registration, to give the organ volume. The inherent accuracy (not including position sensor and segmentation errors) is demonstrated in simulation to be within +/- 2%. The in vivo precision of the complete system is demonstrated (by repeated observations of a human liver) to be +/- 5%.