National Research Council Institute for Biodiagnostics

Fourier transform infrared (FTIR) spectroscopy is an established tool for the structural characterization of proteins. However, many potential pitfalls exist for the unwary investigator. In this review we critically assess the application of FTIR spectroscopy to the determination of protein structure by (1) outlining the principles underlying protein secondary structure determination by FTIR spectroscopy, (2) highlighting the situations in which FTIR spectroscopy should be considered the technique of choice, (3) discussing the manner in which experiments should be conducted to derive as much physiologically relevant information as possible, and (4) outlining current methods for the determination of secondary structure from infrared spectra of proteins.

OBJECTIVES: To evaluate the prevalence and 10-year outcomes of frailty in older adults in relation to deficit accumulation. DESIGN: Prospective cohort study. SETTING: The National Population Health Survey of Canada, with frailty estimated at baseline (1994/95) and mortality follow-up to 2004/05. PARTICIPANTS: Community-dwelling older adults (N=2,740, 60.8% women) aged 65 to 102 from 10 Canadian provinces. During the 10-year follow-up, 1,208 died. MEASUREMENTS: Self-reported health information was used to construct a frailty index (Frailty Index) as a proportion of deficits accumulated in individuals. The main outcome measure was mortality. RESULTS: The prevalence of frailty increased with age in men and women (correlation coefficient=0.955-0.994, P<.001). The Frailty Index estimated that 622 (22.7%, 95% confidence interval (CI)=21.0-24.4%) of the sample was frail. Frailty was more common in women (25.3%, 95% CI=23.2-27.5%) than in men (18.6%, 95% CI=15.9-21.3%). For those aged 85 and older, the Frailty Index identified 39.1% (95% CI=31.3-46.9%) of men as frail, compared with 45.1% (95% CI=39.7-50.5%) of women. Frailty significantly increased the risk of death, with an age- and sex-adjusted hazard ratio for the Frailty Index of 1.57 (95% CI=1.41-1.74). CONCLUSION: The prevalence of frailty increases with age and at any age lessens survival. The Frailty Index approach readily identifies frail people at risk of death, presumably because of its use of multiple health deficits in multidimensional domains.

Confusion exists over the application of the Principle of Reciprocity to NMR signal strength calculations when wavelength in a sample is comparable to the latter's size. A simple and easily reproduced bench experiment that validates the principle is therefore described. Building on the experimental results, elementary mathematics are employed to derive simple equations for the B1 fields in both the negatively and the positively rotating frames. Using these equations, the reader is then guided through the steps needed to deduce correctly the signal received in an NMR experiment. The article should serve as a resource for those attempting signal strength calculations. © 2000 John Wiley & Sons, Inc. Concepts Magn Reson 12: 173–187, 2000

Proton MRS ( 1 H MRS) provides noninvasive, quantitative metabolite profiles of tissue and has been shown to aid the clinical management of several brain diseases. Although most modern clinical MR scanners support MRS capabilities, routine use is largely restricted to specialized centers with good access to MR research support. Widespread adoption has been slow for several reasons, and technical challenges toward obtaining reliable good‐quality results have been identified as a contributing factor. Considerable progress has been made by the research community to address many of these challenges, and in this paper a consensus is presented on deficiencies in widely available MRS methodology and validated improvements that are currently in routine use at several clinical research institutions. In particular, the localization error for the PRESS localization sequence was found to be unacceptably high at 3 T, and use of the semi‐adiabatic localization by adiabatic selective refocusing sequence is a recommended solution. Incorporation of simulated metabolite basis sets into analysis routines is recommended for reliably capturing the full spectral detail available from short TE acquisitions. In addition, the importance of achieving a highly homogenous static magnetic field (B 0 ) in the acquisition region is emphasized, and the limitations of current methods and hardware are discussed. Most recommendations require only software improvements, greatly enhancing the capabilities of clinical MRS on existing hardware. Implementation of these recommendations should strengthen current clinical applications and advance progress toward developing and validating new MRS biomarkers for clinical use.

Image signal-to-noise ratio and power dissipation are investigated theoretically up to 400 MHz. While the text is mathematical, the figures give insights into predictions. Hertz potential is introduced for probe modeling where charge separation cannot be ignored. Using a spherical geometry, the potential from current loops that would produce a homogeneous static B1 field is calculated; at high frequency it is shown to create an unnecessarily inhomogeneous field. However, a totally homogeneous field is shown to be unattainable. Boundary conditions are solved for circularly polarized fields, and strategies for limited shimming of the sample B1 field are then presented. A distinction is drawn between dielectric resonance and spatial field focusing. At high frequency, the region of maximum specific absorption is shown to move inside the sample and decrease. From the fields in both rotating frames, the signal-to-noise ratio is derived and compared with the traditional, low-frequency formulation. On average, it is mostly found to be slightly larger at high frequency. Nevertheless, the free induction decay is sometimes found to be annulled.

Severe acute respiratory syndrome (SARS), a new, highly contagious, viral disease, emerged in China late in 2002 and quickly spread to 32 countries and regions causing in excess of 774 deaths and 8098 infections worldwide. In the absence of a rapid diagnostic test, therapy or vaccine, isolation of individuals diagnosed with SARS and quarantine of individuals feared exposed to SARS virus were used to control the spread of infection. We examine mathematically the impact of isolation and quarantine on the control of SARS during the outbreaks in Toronto, Hong Kong, Singapore and Beijing using a deterministic model that closely mimics the data for cumulative infected cases and SARS-related deaths in the first three regions but not in Beijing until mid-April, when China started to report data more accurately. The results reveal that achieving a reduction in the contact rate between susceptible and diseased individuals by isolating the latter is a critically important strategy that can control SARS outbreaks with or without quarantine. An optimal isolation programme entails timely implementation under stringent hygienic precautions defined by a critical threshold value. Values below this threshold lead to control, but those above are associated with the incidence of new community outbreaks or nosocomial infections, a known cause for the spread of SARS in each region. Allocation of resources to implement optimal isolation is more effective than to implement sub-optimal isolation and quarantine together. A community-wide eradication of SARS is feasible if optimal isolation is combined with a highly effective screening programme at the points of entry.

MOTIVATION: Two practical realities constrain the analysis of microarray data, mass spectra from proteomics, and biomedical infrared or magnetic resonance spectra. One is the 'curse of dimensionality': the number of features characterizing these data is in the thousands or tens of thousands. The other is the 'curse of dataset sparsity': the number of samples is limited. The consequences of these two curses are far-reaching when such data are used to classify the presence or absence of disease. RESULTS: Using very simple classifiers, we show for several publicly available microarray and proteomics datasets how these curses influence classification outcomes. In particular, even if the sample per feature ratio is increased to the recommended 5-10 by feature extraction/reduction methods, dataset sparsity can render any classification result statistically suspect. In addition, several 'optimal' feature sets are typically identifiable for sparse datasets, all producing perfect classification results, both for the training and independent validation sets. This non-uniqueness leads to interpretational difficulties and casts doubt on the biological relevance of any of these 'optimal' feature sets. We suggest an approach to assess the relative quality of apparently equally good classifiers.

A new method for magnetic resonance imaging (MRI) based on the detection of relatively strong signal from intermolecular zero-quantum coherences (iZQCs) is reported. Such a signal would not be observable in the conventional framework of magnetic resonance; it originates in long-range dipolar couplings (10 micrometers to 1 millimeter) that are traditionally ignored. Unlike conventional MRI, where image contrast is based on variations in spin density and relaxation times (often with injected contrast agents), contrast with iZQC images comes from variations in the susceptibility over a distance dictated by gradient strength. Phantom and in vivo (rat brain) data confirm that iZQC images give contrast enhancement. This contrast might be useful in the detection of small tumors, in that susceptibility correlates with oxygen concentration and in functional MRI.

Sixty-four samples from six grade 4 astrocytomas were investigated ex vivo by 1H MRS at 360 MHz and subsequently by histopathology to obtain percentages of viable and necrotic tumour and grey and white matter. MR-visible lipids were detected in 87% of tumour samples. Necrotic foci were < 3 x 3 x 6 mm3. The means of the intensities/unit weight tissue of the lipid resonances at 5.33, 2.80, 1.29 and 0.89 ppm were significantly higher (p < 0.05) for three sets of comparisons: samples with 85-100% vs 50-75%; with 50-75% vs 10-40% and with 10-40% vs 0-5% necrosis. For the lipid resonance at 2.04 ppm the difference in the means was significant only for samples with 50-75% compared to those with 85-100% necrosis, because for samples with < 50% necrosis resonances from glutamine and possibly small amounts of glutamate, gamma-aminobutyrate and N-acetylaspartate anions contribute significantly to the spectral area at 2.0 ppm. We conclude that necrotic foci below MRI resolution yield the resonances at 1.3 and 0.9 ppm, and contribute to the intense resonance at 2.0 ppm observed in in vivo 1H spectra of some high grade astrocytomas.

A mouse model of glioblastoma multiforme was used to determine the accumulation of a targeted contrast agent in tumor vessels. The contrast agent, consisting of superparamagnetic iron oxide coated with dextran, was functionalized with an anti-insulin-like-growth-factor binding protein 7 (anti-IGFBP7) single domain antibody. The near infrared marker, Cy5.5, was also attached for an in vivo fluorescence study. A 9.4T magnetic resonance imaging (MRI) system was used for in vivo studies on days 10 and 11 following tumor inoculation. T(2) relaxation time was used to measure the accumulation of the contrast agent in the tumor. Changes in tumor to brain contrast because of active targeting were compared with a nontargeted contrast agent. Effective targeting was confirmed with near infrared measurements and fluorescent microscopic analysis. The results showed that there was a statistically significant (P < .01) difference in normalized T(2) between healthy brain and tumor tissue 10 min, 1 h, and 2 h point postinjection of the anti-IGFBP7 single domain antibody targeted and nontargeted iron oxide nanoparticles. A statistical difference remained in animals treated with targeted nanoparticles 24 h postinjection only. The MRI, near infrared imaging, and fluorescent microscopy studies showed corresponding spatial and temporal changes. We concluded that the developed anti-IGFBP7-iron oxide single domain antibody-targeted MRI contrast agent selectively binds to abnormal vessels within a glioblastoma. T(2)-weighted MRI and near infrared imaging are able to detect the targeting effects in brain tumors.

BACKGROUND: Abnormalities in limbic structures have been implicated in major depressive disorder (MDD). Although MDD is as common in adolescence as in adulthood, few studies have examined youth near illness onset in order to determine the possible influence of atypical development on the pathophysiology of this disorder. METHODS: Hippocampal volumes were measured in 17 MDD subjects (age = 16.67 +/- 1.83 years [mean +/- SD]; range = 13 - 18 years) and 17 age- and sex-matched healthy controls (16.23 +/- 1.61 years [mean +/- SD]; 13 - 18 years) using magnetic resonance imaging (MRI). RESULTS: An analysis of covariance revealed a significant difference between MDD and control subjects (F = 8.66, df = 1, 29, P = 0.006). This was more strongly localized to the left hippocampus (P = 0.001) than the right hippocampus (P = 0.047). CONCLUSIONS: Our findings provide new evidence of abnormalities in the hippocampus in early onset depression. However, our results should be considered preliminary given the small sample size studied.

Clusters of iron oxide nanoparticles encapsulated in a pH-responsive hydrogel are synthesized and studied for their ability to alter the T(2)-relaxivity of protons. Encapsulation of the clusters with the hydrophilic coating is shown to enhance the transverse relaxation rate by up to 85% compared to clusters with no coating. With the use of pH-sensitive hydrogel, difficulties inherent in comparing particle samples are eliminated and a clear increase in relaxivity as the coating swells is demonstrated. Agreement with Monte Carlo simulations indicates that the lower diffusivity of water inside the coating and near the particle surface leads to the enhancement. This demonstration of a surface-active particle structure opens new possibilities in using similar structures for nanoparticle-based diagnostics using magnetic resonance imaging.

The use of body coils is favored for homogeneous excitation, and such coils are often paired with surface coils or arrays for sensitive reception in many MRI applications. While the body coil's physical size and resultant electrical length make this circuit difficult to design for any field strength, recent efforts to build efficient body coils for applications at 3T and above have been especially challenging. To meet this challenge, we developed an efficient new transverse electromagnetic (TEM) body coil and demonstrated its use in human studies at field strengths up to 4 T. Head, body, and breast images were acquired within peak power constraints of <8 kW. Bench studies indicate that these body coils are feasible to 8 T. RF shimming was used to remove a high-field-related cardiac imaging artifact in these preliminary studies. P41RR13230

A major limitation of the commonly used clinical MRI contrast agents (CAs) suitable at lower magnetic field strengths (<3.0 T) is their inefficiency at higher fields (>7 T), where next-generation MRI scanners are going. We present dysprosium nanoparticles (β-NaDyF4 NPs) as T2 CAs suitable at ultrahigh fields (9.4 T). These NPs effectively enhance T2 contrast at 9.4 T, which is 10-fold higher than the clinically used T2 CA (Resovist). Evaluation of the relaxivities at 3 and 9.4 T show that the T2 contrast enhances with an increase in NP size and field strength. Specifically, the transverse relaxivity (r2) values at 9.4 T were ∼64 times higher per NP (20.3 nm) and ∼6 times higher per Dy(3+) ion compared to that at 3 T, which is attributed to the Curie spin relaxation mechanism. These results and confirming phantom MR images demonstrate their effectiveness as T2 CAs in ultrahigh field MRIs.

BACKGROUND/AIMS: Puckered, dimply skin on the thighs, hips, and buttocks is known as cellulite. The cause of cellulite is not known, although there are a number of different hypotheses. In this study, we use magnetic resonance (MR) micro-imaging to study cellulite skin. To the best of our knowledge, this is the first reported MR study of cellulite. METHODS: High-resolution in vivo MR images of the postlateral thigh skin of two male groups and four female groups were obtained. Subjects were grouped according to their body mass index (BMI) and cellulite grade. A qualitative assessment of how MRI can be used to differentiate skin tissue at different levels of cellulite grading was performed. RESULTS: We found that changes in skin architecture with cellulite can be visualized by in vivo MR micro-imaging. The skin fat layers beneath the dermis and down to the level of muscles are well visualized in the images. Also, the diffuse pattern of extrusion of underlying adipose tissue into dermis is clearly imaged, and was found to correlate with cellulite grading. We also show that other skin tissue parameters such as (a) the percentile of adipose vs. connective tissue in a given volume of hypodermis and (b) the percentile of hypodermic invaginations inside the dermis are correlated with cellulite grade. CONCLUSION: MR images can be interpreted to measure tissue parameters correlated with cellulite. Considering that we had only three subjects in each group, the achievements of this pilot study were highly satisfactory. We have shown that the in vivo micro-MR is a technique able to detect the effects of cellulite and gender. This study can be extended for further investigations of drugs and/or medical devices for cellulite treatment.

Cation exchange was performed on up-conversion NaYF4:Yb,Tm nanoparticles, resulting in NaYF4:Yb,Tm-NaGdF4 core–shell nanoparticles as indicated by electron energy-loss spectroscopy 2D mapping. Results show that core–shell nanoparticles with a thin, tunable, and uniform shell of subnanometer thickness can be made via this cation exchange process. The resulting NaYF4:Yb,Tm-NaGdF4 core–shell nanoparticles have an enhanced up-conversion intensity relative to the initial core nanoparticles. As potential magnetic resonance imaging (MRI) contrast agents, they were tested for their proton relaxivities. The r1 relaxivity per Gd3+ ion of the nanoparticles with a thin NaGdF4 shell (ca. 0.6 nm thick) measured at 9.4 T was found to be 2.33 mM–1·s–1. This r1 relaxivity is among the highest in all the reported NaYF4–NaGdF4 core–shell nanoparticles. The r1 relaxivity per nanoparticle is 1.56 × 104 mM–1·s–1, which is over 4000 times higher than commercial Gd3+-complexes. The very high proton relaxivity per nanoparticle is critical for targeted MRI as such nanoparticles provide strong contrast even in low concentrations. The presented cation exchange method is a promising way to manufacture core–shell nanoparticles with up-conversion NaYF4:Yb,Tm core and paramagnetic NaGdF4 shell for bimodal imaging, i.e. MR and optical imaging.

Abstract Fourier transform infrared spectroscopy has been applied to the study of human breast tumors, human breast tumor cell lines and xenografted human tumor cells. The results presented indicate that substantial differences exist on a macroscopic level between human tumors, xenografted tumors and human tumor cell lines, which are related to the presence of a significant connective tissue matrix in the tumors. On a macroscopic level tumor cell xenografts appear, in spectroscopic terms, to be relatively homogeneous with a relatively weak signature characteristic of connective tissue. Differences on a microscopic level between adjacent small (30 μm 2 ) areas of the same xenografted tumor could be detected, which were due to local variations in collagen content. In addition to variations in collagen content, variation in the deposition of microscopic fat droplets throughout both human and xenografted tumors could be detected. These results indicate the care with which infrared spectroscopic studies of tissues must be carried out to avoid incorrect interpretation of results due to an incomplete understanding of tissue pathology. © 1995 John Wiley &amp; Sons, Inc.

This study assesses the potential for using mid-infrared (mid-IR) spectroscopy of dried serum films as the basis for the simultaneous quantitation of eight serum analytes: total protein, albumin, triglycerides, cholesterol, glucose, urea, creatinine and uric acid. Infrared transmission spectra were acquired for 300 serum samples, each analysed independently using accepted reference clinical chemical methods. Quantitation methods were based upon the infrared spectra and reference analyses for 200 specimens, and the models validated using the remaining 100 samples. Standard errors in the IR-predicted analyte levels (Sy/x) were 2.8 g/L (total protein), 2.2 g/L (albumin), 0.23 mmol/L (triglycerides), 0.28 mmol/L (cholesterol), 0.41 mmol/L (glucose) and 1.1 mmol/L for urea, with correlation coefficients (IR vs reference analyses) of 0.95 or better. The IR method emerged to be less suited for creatinine (Sy/x = mumol/L) and uric acid (Sy/x = 140 mumol/L) due to the relatively low concentrations typical of these analytes.

BACKGROUND AND PURPOSE: VRSs are the perivascular spaces surrounding the deep perforating arteries in the brain. Although VRS variations with age and disease pathologies have been reported previously, the radiologic characteristics of the VRS in relation to AD are poorly understood. This study investigated the prevalence, spatial distribution, and severity of the VRS in AD, MCI, and older adults who were CN. It also investigated the relationship of the VRS to white matter changes. MATERIALS AND METHODS: Structural MR imaging data were acquired from 158 participants (AD = 37, MCI = 71, CN = 50, mean age = 74.97 ± 7.20 years) who had undergone T1WI at 3T. The severity of VRS in the white matter, basal ganglia, hippocampus, and brain stem structures was evaluated by using a semiquantitative scale, adapted from existing rating scales. A VRS total score summarizing the subscales was calculated to assess the whole-brain VRSs. RESULTS: VRSs were observed in multiple brain regions of all participants, typically presented as <2-mm well-margined symmetric round-, oval- and linear-shaped hypointensities on T1WI. The VRS total score increased with leukoaraiosis, atrophy, and advanced age (P < .001). Individuals with AD and MCI showed greater levels of VRS than control subjects. The VRS total score discriminated individuals with AD and those who were CN with an accuracy of 0.79 (95% CI, 0.69-0.89). CONCLUSIONS: VRSs are common in older adults and are more severe in AD and MCI than in CN. Whether increased VRSs can be reliably used to aid in AD diagnosis warrants further investigation.

This study assessed the potential therapeutic efficacy of adipose-derived stem cells (ASCs) on infarcted hearts. Myocardial infarction was induced in rat hearts by occlusion of the left anterior descending artery (LAD). One week after LAD occlusion, the rats were divided into three groups and subjected to transplantation of ASCs or transplantation of cell culture medium (CCM) or remained untreated. During a 1-mo recovery period, magnetic resonance imaging showed that the ASC-treated hearts had a significantly greater left ventricular (LV) ejection fraction and LV wall thickening than did the CCM-treated and untreated hearts. The capillary density in infarct border zone was significantly higher in the ASC-treated hearts than in the CCM-treated and untreated hearts. However, only 0.5% of the ASCs recovered from the ASC-treated hearts were stained positive for cardiac-specific fibril proteins. It was also found that ASCs under a normal culture condition secreted three cardiac protective growth factors: vascular endothelial growth factor, hepatocyte growth factor, and insulin-like growth factor-1. Results of this study suggest that ASCs were able to improve cardiac function of infarcted rat hearts. Paracrine effect may be the mechanism underlying the improved cardiac function and increased capillary density.