Ppm Signal Research Articles

Energy-Efficient Low-Complexity Detection of PPM Signals at the Presence of Monobit Quantisation

Energy-Efficient Low-Complexity Detection of PPM Signals at the Presence of Monobit Quantisation

Long-range underwater wireless optical communication system based on 490 nm vertical-external-cavity surface-emitting laser

The exploration and utilization of marine resources has promoted the rapid development of marine science and technology, and has put forward higher requirements for underwater communication technology. Long distance underwater wireless optical communication (UWOC) requires the selection of light source on the transmitter side. Laser diodes (LDs) have excellent portability and maneuverability, and have been widely used in the UWOC systems. However, their beam quality is not so good and it is difficult to modulate under high power. In recent years, vertical-external-cavity surface-emitting laser (VECSEL) has received much attention due to its high output power and good beam quality. This work is to explore the advantages of using a 490-nm blue VECSEL as a light source in UWOC, and to improve the performance of the UWOC system by the soft-decision pulse-position modulation (PPM). First, the optical power attenuation coefficient of the channel is obtained, and the measured <i>c</i> is about 0.0591 m<sup>–1</sup> in a 96-m-long tap channel. Subsequently, soft-decision and hard-decision are simulated and experimentally verified. Both simulations and measurements show that the bit error rate (BER) can be significantly reduced with soft-decision. Afterwards, we improve the system by using the soft-decision algorithm and investigate the communication performance of 64 PPMs at different bandwidths by adjusting the PPM signal rate. Finally, 50 MHz is chosen as a signal rate in the experiment. Then a UWOC system is demonstrated in this work. The transmitter side consists of a 490-nm VECSEL light source with an acousto-optic modulator (AOM). The pseudo-random binary sequence (PRBS) is loaded into the arbitrary waveform generator (AWG) for digital-to-analog conversion after PPM modulation, and the analog signal is sent to the driver of the AOM for acousto-optic modulation of the incident beam. The laser is focused before entering the AOM and then collimated after having exited to reduce its divergence. The modulated laser beam passes through a distance of 96 m in the tank by using multiple mirrors on both sides of the tank. Then, the beam is focused by a lens to the avalanche photodiode (APD) for photoelectric conversion in the end, and the signal is processed by a mixed signal oscilloscope (MSO) after data acquisition. A soft-decision algorithm is introduced to further optimize the performance of the PPM modulation. When the optical signal passes through a relatively long distance of 96 m, the measured BER is as low as 1.9 × 10<sup>–5</sup>. This indicates that the soft-decision PPM-based 490 nm blue VECSEL UWOC system performs very well.

Photocount Characteristics of SNSPD for PPM Signals in Deep-Space Laser Communication (Invited)

Photocount Characteristics of SNSPD for PPM Signals in Deep-Space Laser Communication (Invited)

Probing covalent and non-covalent interactions between vanillic acid and starch and their effects on digestibility by solid-state NMR

Intermolecular interactions play a significant role on the physicochemical properties and digestibility of starchy foods. This study investigated the covalent and non-covalent interactions between vanillic acid (VA) and porous starch (PS) as well as their effects on digestibility using solid-state NMR. VA-PS conjugates and mixtures were synthesized and characterized using 1H NMR, FT-IR, SEM and XRD. 13C NMR peaks at 163 ppm and FT-IR signals at 1737 cm−1 indicated the formation of ester bond in VA-PS conjugates. While differences between covalent and non-covalent interactions were also probed by solid-state NMR. The specific binding sites between VA and PS were subsequently identified by 1H13C HETCOR spectra before assessing the impact of covalent and non-covalent interactions on digestibility through an in vitro digestion test. The results revealed 13C chemical shifts of about 2.0 ppm, indicating stronger intermolecular interactions, and reduced mobility of the VA-PS conjugate due to its covalent bonding. Overall, the results showed that the VA-PS conjugate, characterized by stronger covalent interactions, exhibited superior effects in inhibiting starch digestibility compared with non-covalent interactions.

Fucosylated heparan sulfate from the midgut gland of Patinopecten yessoensis

The structural and functional relationships of glycosaminoglycans (GAGs) derived from marine organisms have been investigated, suggesting that marine invertebrates, particularly Bivalvia, are abundant sources of highly sulfated or branched GAGs. In this study, we identified a novel fucosylated heparan sulfate (Fuc-HS) from the midgut gland of the Japanese scallop, Patinopecten yessoensis. Scallop HS showed resistance to GAG-degrading enzymes, including chondroitinases and heparinases, and susceptibility to heparinases increased when scallop HS was treated with mild acid hydrolysis, which removes the fucosyl group. Moreover, 1H NMR detected significant signals near 1.2–1.3 ppm corresponding to the H-6 methyl proton of fucose residues and small H-3 (3.59 ppm) or H-2 (3.39 ppm) signals of glucuronate (GlcA) were detected, suggesting that the fucose moiety is attached to the C-3 position of GlcA in scallop HS. GC–MS detected peaks corresponding to 1, 3, 5-tri-O-acetyl-2, 4-di-O-methyl-L-fucitol and 1, 4, 5-tri-O-acetyl-2, 3-di-O-methyl-L-fucitol, suggesting that the fucose moiety is 3-O- or 4-O-sulfated. Furthermore, scallop HS showed anti-coagulant and neurite outgrowth-promoting (NOP) activities. These results suggest that the midgut gland of scallops is a valuable source of Fuc-HS with biological activities.

Assignment of molecular origins of NOE signal at -3.5ppm in the brain.

Nuclear Overhauser enhancemen mediated saturation transfer effect, termed NOE (-3.5ppm), is a major source of CEST MRI contrasts at 3.5ppm in the brain. Previous phantom experiments have demonstrated that both proteins and lipids, two major components in tissues, have substantial contributions to NOE (-3.5ppm) signals. Their relative contributions in tissues are informative for the interpretation of NOE (-3.5ppm) contrasts that could provide potential imaging biomarkers for relevant diseases, which remain incompletely understood. Experiments on homogenates and supernatants of brain tissues collected from healthy rats, that could isolate proteins from lipids, were performed to evaluate the relative contribution of lipids to NOE (-3.5ppm) signals. On the other hand, experiments on ghost membranes with varied pH, and reconstituted phospholipids with different chemical compositions were conducted to study the dependence of NOE (-3.5ppm) on physiological conditions. Besides, CEST imaging on rat brains bearing 9L tumors and healthy rat brains was performed to analyze the causes of the NOE (-3.5ppm) contrast variations between tumors and normal tissues, and between gray matter and white matter. Our experiments reveal that lipids have dominant contributions to the NOE (-3.5 ppm) signals. Further analysis suggests that decreased NOE (-3.5ppm) signals in tumors and higher NOE (-3.5ppm) signals in white matter than in gray matter are mainly explained by changes in membrane lipids, rather than proteins. NOE (-3.5ppm) could be exploited as a highly sensitive MRI contrast for imaging membrane lipids in the brain.

A Technique for Measuring Dynamic Slot-Power of Optical PPM Signals Based on SNSPD

We propose a method to accurately measure dynamic slot-power of optical signal by using the SNSPD under extremely low received power. Experimental results demonstrate that our method can measure power below −130 dBm. The uncertainty of this method can be less than 5%, and frequency of measured signal can be up to 100 Mbps.

Experiments on the thermal activation of hydrogen release of NaBH4-sodalites characterized by IR- and MAS-NMR spectroscopy

New results on the reactions of the (BH4)-anion enclathrated in the cages of sodalites are reported. Hydrothermally synthesized NaBH4-sodalites (ǀNa8(BH4)2ǀ[SiAlO4]6) always contain hydro-sodalite type cages (ǀNa3(H2O)4ǀ[SiAlO4]3). With increasing temperature dehydration occurs. Above 250 °C a limited reaction of the residual water is going on with (BH4)-cage fillings releasing hydrogen and the appearance of certain borate specifications enclosed in the sodalite cages. The effect of a reaction of oxygen with the (BH4)-anions in the sodalite-cages at temperatures above 400 °C is also shown. The degree of (BH4)-conversion using wet and dry N2 stream is further followed by IR and MAS NMR investigations. External supply of water largely enhances the degree of reaction, e.g. at 400 °C from 16% to 44% loss of (BH4)-absorption intensity. However, 11B MAS NMR shows 8% and 22% of a conversion of (BH4)-cage fillings into new borate species in dry and wet N2 stream, respectively. These lower values are explained by a loss of B-ions via formation and evaporation of BH3 from the sodalite. Further evaluation of the 11B MAS NMR spectra could resolve the formation of (B(OH)3)-, (BO(OH)2)-, (B(OH)4)- along with unreacted (BH4)-species in the cages. 1H-MAS NMR shows a −3.8 ppm signal related to cage isolated (OH)-, which suggests an initial reaction step via (H+ + BH4−) to (BH3 + H2). The formation of (B(OH)3), however, also indicated sufficient water for a reaction of BH3 releasing further hydrogen. The formation of (BH3) could be observed in temperature dependent IR investigations at temperatures above 400 °C.

Free-breathing 3D CEST MRI of human liver at 3.0T.

To develop a novel 3D abdominal CEST MRI technique at 3 T using MR multitasking, which enables entire-liver coverage with free-breathing acquisition. k-Space data were continuously acquired with repetitive steady-state CEST (ss-CEST) modules. The stack-of-stars acquisition pattern was used for k-space sampling. MR multitasking was used to reconstruct motion-resolved 3D CEST images of 53 frequency offsets with entire-liver coverage and 2.0 × 2.0 × 6.0 mm3 spatial resolution. The total scan time was 9min. The sensitivity of amide proton transfer (APT)-CEST (magnetization transfer asymmetry [MTRasym ] at 3.5ppm) and glycogen CEST (glycoCEST) (mean MTRasym around 1.0ppm) signals generated with the proposed method were tested with fasting experiments. Both APT-CEST and glycoCEST signals showed high sensitivity between post-fasting and post-meal acquisitions. APT-CEST and glycoCEST MTRasym signals from post-mean scans were significantly increased (APT-CEST: -0.019 ± 0.017 in post-fasting scans, 0.014 ± 0.021 in post-meal scans, p < 0.01; glycoCEST: 0.003 ± 0.009 in post-fasting scans, 0.027 ± 0.021 in post-meal scans, p < 0.01). The proposed 3D abdominal steady-state CEST method using MR multitasking can generate CEST images of the entire liver during free breathing.

Carrier-Free Deferoxamine Nanoparticles against Iron Overload in Brain

Carrier-Free Deferoxamine Nanoparticles against Iron Overload in Brain

Deep neural network based CEST and AREX processing: Application in imaging a model of Alzheimer's disease at3T.

To optimize and apply deep neural network based CEST (deepCEST) and apparent exchange dependent-relaxation (deepAREX) for imaging the mouse brain with Alzheimer's disease (AD) at 3T MRI. CEST and T1 data of central and anterior brain slices of 10 AD mice and 10 age-matched wild type (WT) mice were acquired at a 3T animal MRI scanner. The networks of deepCEST/deepAREX were optimized and trained on the WT data. The CEST/AREX contrasts of AD and WT mice predicted by the networks were analyzed and further validated by immunohistochemistry. After optimization and training on CEST data of WT mice, deepCEST/deepAREX could rapidly (~1 s) generate precise CEST and AREX results for unseen CEST data of AD mice, indicating the accuracy and generalization of the networks. Significant lower amide weighted (3.5 ppm) signal related to amyloid β-peptide (Aβ) plaque depositions, which was validated by immunohistochemistry results, was detected in both central and anterior brain slices of AD mice compared to WT mice. Decreased magnetization transfer (MT) signal was also found in AD mice especially in the anterior slice. DeepCEST/deepAREX could rapidly generate accurate CEST/AREX contrasts in animal study. The well-optimized deepCEST/deepAREX have potential for AD differentiation at 3T MRI.

Factors controlling age quality in U[sbnd]Pb dated Plio-Pleistocene speleothems from South Africa: The good, the bad and the ugly.

Caves in South Africa preserve a rich record of early hominin and early modern human development and have been the subject of much research. UPb dating of speleothems, particularly flowstones, has provided a much-needed chronology for cave sites in the Cradle of Humankind, the coastal cliff caves at Pinnacle Point and at the archaeological site of Wonderwerk Cave. The UPb ages range from ~3 Ma to just under 1 Ma and altogether represent a relatively large dataset of 35 U-Pb ages, from 34 flowstone samples, consisting of a total of 291 individual matched U and Pb isotope analyses. We look for patterns within these data and find that in general, the U concentration has little to no effect on age quality, while the lower Pb concentration, the better. Our data confirms the expected negative exponential relationship between UPb age and 234U/238U. There is no apparent relationship between U concentration and residual 234U/238U, suggesting U concentration patterns are controlled by 238U, not 234U. We divide the 35 U-Pb ages into three categories defined by the % error on the UPb age (the good, the bad and the ugly). We use the U and Pb isotope data, thin section petrography and laser ablation trace element transects through the flowstones to investigate the factors controlling the quality of the ages. The ‘good’ ages are produced by the coincidence of several features: a large number of points (10 or more) defining their isochrons, radiogenic 206Pb/204Pb ratios, with a few very radiogenic points defining the line of the isochron, U concentrations of ~1 ppm and well-preserved trace element signals. ‘Bad’ ages are caused by deficit in one of these factors but may be redeemed with additional analysis to better define the line of isochron and constrain initial 234U/238U. The ‘ugly’ ages are attributable to low levels of radiogenic Pb, a low spread of isochron and high Pb concentrations, possibly from detrital material. We show what a completely recrystallized flowstone looks like, where the original trace element signals are completely obliterated, and it is impossible to resolve a UPb age. The thin section petrography reveals all flowstones have undergone heavy diagenesis, with the dominant fabric observed consisting of mosaic calcite with relic aragonite. However, we argue that the preservation of trace element signals, in particular the abrupt, sympathetic step-like variation is Sr, U and in some cases Ba and Mg, indicate that this diagenesis is conservative. We identify a mixture of crystal and fluid dominated trace element patterns, both of which are ultimately related to flow dynamics, in turn related to changes in external hydroclimate. This hints at the potential to extract valuable palaeoclimate records out of these old, UPb dated flowstones, which would be very interesting given their association with important early human evolution sites in South Africa.

Simultaneous quantification of GABA, Glx and GSH in the neonatal human brain using magnetic resonance spectroscopy

Balance between inhibitory and excitatory neurotransmitter systems and the protective role of the major antioxidant glutathione (GSH) are central to early healthy brain development. Disruption has been implicated in the early life pathophysiology of psychiatric disorders and neurodevelopmental conditions including Autism Spectrum Disorder.Edited magnetic resonance spectroscopy (MRS) methods such as HERMES have great potential for providing important new non-invasive insights into these crucial processes in human infancy. In this work, we describe a systematic approach to minimise the impact of specific technical challenges inherent to acquiring MRS data in a neonatal population, including automatic segmentation, full tissue-correction and optimised GABA+ fitting and consider the minimum requirements for a robust edited-MRS acquisition. With this approach we report for the first time simultaneous GABA+, Glx (glutamate + glutamine) and GSH concentrations in the neonatal brain (n = 18) in two distinct regions (thalamus and anterior cingulate cortex (ACC)) using edited MRS at 3T.The improved sensitivity provided by our method allows specific regional neurochemical differences to be identified including: significantly lower Glx and GSH ratios to total creatine in the thalamus compared to the ACC (p < 0.001 for both), and significantly higher GABA+ and Glx levels in the ACC following tissue-correction (p < 0.01). Furthermore, in contrast to adult GABA+ which can typically be accurately fitted with a single peak, all neonate spectra displayed a characteristic doublet GABA+ peak at 3 ppm, indicating a lower macromolecule (MM) contribution to the 3 ppm signal in neonates. Relatively high group-level variance shows the need to maximise voxel size/acquisition time in edited neonatal MRS acquisitions for robust estimation of metabolites.Application of this method to study how these levels and balance are altered by early-life brain injury or genetic risk can provide important new knowledge about the pathophysiology underlying neurodevelopmental disorders.

A conspicuous 27Al-NMR signal at 72 ppm during isomerization of Keggin Al13 ions

A sharp signal at 72 ppm was recently observed in 27Al-NMR spectra during the isomerization of Keggin-Al13 ions in the presence of calcium and glycine [1]. It has been proposed that this signal corresponds to one of the Keggin isomers. Conversion of the most common ε-isomer of the Keggin series of molecules, having the stoichiometry [AlO4Al12(OH)24(OH2)12]7+, is enhanced by the addition of calcium and glycine [2,3]. Here we show that a 72 ppm signal can also be observed in the absence of calcium or glycine; the magnitude of which depends on aluminum concentration and temperature. Additionally, isomerization of the ε-Keggin-Al13 to the γ-Keggin-Al13 isomer was observed in the absence of calcium and glycine at elevated temperatures after several days. Calcium and glycine were previously shown to enhance rates of γ-Keggin-Al13 formation.2.

Amplified detection of phosphocreatine and creatine after supplementation using CEST MRI at high and ultrahigh magnetic fields

Creatine is an important metabolite involved in muscle contraction. Administration of exogenous creatine (Cr) or phosphocreatine (PCr) has been used for improving exercise performance and protecting the heart during surgery including during valve replacements, coronary artery bypass grafting and repair of congenital heart defects. In this work we investigate whether it is possible to use chemical exchange saturation transfer (CEST) MRI to monitor uptake and clearance of exogenous creatine and phosphocreatine following supplementation. We were furthermore interested in determining the limiting conditions for distinguishing between creatine (1.9 ppm) and phosphocreatine (2.6 ppm) signals at ultra-high fields (21 T) and determine their concentrations could be reliably obtained using Bloch equation fits of the experimental CEST spectra. We have tested these items by performing CEST MRI of hind limb muscle and kidneys at 11.7 T and 21.1 T both before and after intravenous administration of PCr. We observed up to 4% increase in contrast in the kidneys at 2.6 ppm which peaked ~30 min after administration and a relative ratio of 1.3 in PCr:Cr signal. Overall, these results demonstrate the feasibility of independent monitoring of PCr and Cr concentration changes using CEST MRI.

In vivo MRS measurement of 2-hydroxyglutarate in patient-derived IDH-mutant xenograft mouse models versus glioma patients.

To generate a preclinical model of isocitrate dehydrogenase (IDH) mutant gliomas from glioma patients and design a MRS method to test the compatibility of 2-hydroxyglutarate (2HG) production between the preclinical model and patients. Five patient-derived xenograft (PDX) mice were generated from two glioma patients with IDH1 R132H mutation. A PRESS sequence was tailored at 9.4 T, with computer simulation and phantom analyses, for improving 2HG detection in mice. 2HG and other metabolites in the PDX mice were measured using the optimized MRS at 9.4 T and compared with 3 T MRS measurements of the metabolites in the parental-tumor patients. Spectral fitting was performed with LCModel using in-house basis spectra. Metabolite levels were quantified with reference to water. The PRESS TE was optimized to be 96 ms, at which the 2HG 2.25 ppm signal was narrow and inverted, thereby leading to unequivocal separation of the 2HG resonance from adjacent signals from other metabolites. The optimized MRS provided precise detection of 2HG in mice compared to short-TE MRS at 9.4 T. The 2HG estimates in PDX mice were in excellent agreement with the 2HG measurements in the patients. The similarity of 2HG production between PDX models and parental-tumor patients indicates that PDX tumors retain the parental IDH metabolic fingerprint and can serve as a preclinical model for improving our understanding of the IDH-mutation associated metabolic reprogramming.

NIMG-70. A LABEL-FREE APPROACH TO ASSESS CHEMOTHERAPY DRUG CONCENTRATION USING CHEMICAL EXCHANGE SATURATION TRANSFER MRI – A FEASIBILITY STUDY

Abstract BACKGROUND Drug delivery is one of the most pressing problems in neuro-oncology as the blood-brain barrier (BBB) uniquely limits penetration of substances into the brain parenchyma. Plasma and CSF drug concentrations are relatively easy to measure, but do not necessarily reflect concentrations in the brain. Furthermore, invasive measurements may be inaccurate in regions of heterogeneous BBB integrity. Advanced non-invasive imaging approaches may help bridge this information gap without the added risk. Chemical exchange saturation transfer (CEST) is an MRI technique that allows in vivo detection of molecules with a suitable hydrogen exchange rate, such as methotrexate (MTX). High-dose MTX is commonly used in oncology and its concentrations in urine (&gt;2000µM), plasma (&gt;1000µM) and enhancing brain tumors (&gt;350µM) are well above the theoretical threshold of CEST. AIM: We aimed to confirm the CEST detectability of MTX in vitro, and to estimate the currently lowest measurable concentrations in solutions mimicking bodily fluids. METHODS We used a 9.4T MRI to assess the spectra of MTX at 37°C at various concentrations (0.1–10.0 mM) in a phosphate-buffered saline (PBS) solution at various pH (6.0–8.0), as well as in synthetic urine at pH 6.2. RESULTS CEST signals attributable to MTX at 1.5 and 2.7ppm were successfully detected in PBS at concentrations as low as 500µM. The optimal field strength was 3.6µT. While increasing pH increased the detection threshold of the 2.7ppm signal, the 1.5ppm signal was minimally affected by pH within physiologic ranges. In synthetic urine, the MTX CEST signal was well-detectable even at concentrations as low as 200µM. CONCLUSIONS These preliminary results suggest that MTX-CEST may be feasible at field strengths achievable in clinical scanners and at MTX concentrations previously measured in enhancing brain tumors treated with high-dose MTX. Further optimization of the technique for in human use is under way.

REACTION OF ACETONE WITH DIETHYL OXALATE FOLLOWED BY AZOCOUPLING

Condensation of acetone with diethyl oxalate in presence of sodium hydride followed by the action of a mixture of arylamine, hydrochloric acid and sodium nitrite in neutral medium in an equimolar ratio yields 3-arylhydrazono-2,4-dioxopentanoates. The method proposed is simple and convenient, it makes possible to obtain a variety of previously unknown 3-arylhydrazono-2,4-dioxoalkanoates. The target compounds are obtained with the yield of more than 35%, and it favours to produce single crystals for study of the crystal structure of the synthesized compounds by X-ray diffraction analysis. It was found that in the crystalline state synthesized compounds form the E-isomer. The structural features of 3-arylhydrazono-2,4-dioxopentanoates obtained are established by IR and NMR 1H spectroscopy. In the NMR 1H spectra, the signals of the proton-containing groups of 3-arylhydrazono-2,4-dioxopentanoates with comparable integral intensity values are detected in the expected region. In a weak field (15.00 - 15.08 ppm) signals of NH-protons are observed, which indicates the intramolecular hydrogen bond. It is shown that the ratio of reagents and pH of the medium affects the direction of further azocoupling by diazonium salts after acetone treated with diethyl oxalate. Thus, 1,5-diaryl-3-acetylformazanes were isolated in the alkaline medium with double excess of aryldiazonium chlorides by 35 – 37% yield. The identity of synthesized compounds is confirmed by thin layer chromatography, and their structure is proved by IR and NMR 1H spectroscopy data. The proposed structure of the isolated 1,5-diaryl-3-acetylformazans is the most preferred and characteristic of most formazans. NH-proton signals are observed in a weak field at 15.87 ppm. and 16.0 ppm the resulting 1,5-diaryl-3-acetylformazans, which indicates the formation of the hydrogen bond -NH ... N = N-type in the six-membered chelate cycle with the possibility of proton transfer.

Protein aggregation linked to Alzheimer's disease revealed by saturation transfer MRI

The goal of this study was to develop a molecular biomarker for the detection of protein aggregation involved in Alzheimer's disease (AD) by exploiting the features of the water saturation transfer spectrum (Z-spectrum), the CEST signal of which is sensitive to the molecular configuration of proteins. A radial-sampling steady-state sequence based ultrashort echo time (UTE) readout was implemented to image the Z-spectrum in the mouse brain, especially the contributions from mobile proteins at the frequency offsets for the composite protein amide proton (+3.6 ppm) and aliphatic proton (−3.6 ppm) signals. Using a relatively weak radiofrequency (RF) saturation amplitude, contributions due to strong magnetization transfer contrast (MTC) from solid-like macromolecules and direct water saturation (DS) were minimized. For practical measure of the changes in the mobile protein configuration, we defined a saturation transfer difference (ΔST) by subtracting the Z-spectral signals at ±3.6 ppm from a control signal at 8 ppm. Phantom studies of glutamate solution, protein (egg white) and hair conditioner show the capability of the proposed scheme to minimize the contributions from amine protons, DS, and MTC, respectively. The ST signal at ±3.6 ppm of the cross-linked bovine serum albumin (BSA) solutions demonstrated that the ΔST signal can be used to monitor the aggregation process of the mobile proteins. High-resolution ΔST images of AD mouse brains at ±3.6 ppm of mouse brains showed significantly reduced ΔST (-3.6) signal compared to the age-matched wild-type (WT) mice. Thus, this signal has potential to serve as a molecular biomarker for monitoring protein aggregation in AD.

Quantification of Propionic Acid in the Bovine Spinal Disk After Infection of the Tissue With Propionibacteria acnes Bacteria.

Research. The goal of this study was to investigate whether Propionibacteria acnes infection of the intervertebral disc can be detected noninvasively by nuclear magnetic resonance (NMR) spectroscopy. Microbiological studies of surgical samples suggest that a significant subpopulation of back pain patients may have occult disc infection with P. acnes bacteria. This hypothesis is further supported by a double-blind clinical trial showing that back pain patients with Modic type 1 changes may respond to antibiotic treatment. Because significant side effects are associated with antibiotic treatment, there is a need for a noninvasive method to detect whether specific discs in back pain patients are infected with P acnes bacteria. P. acnes bacteria were obtained from human patients. NMR detection of a propionic acid (PA) in the bacteria extracts was conducted on 500 MHz high-resolution spectrometer, whereas in vivo NMR spectroscopy of an isolated bovine disk tissue infected with P. acnes was conducted on 7 T magnetic resonance imaging scanner. NMR spectra of P. acnes metabolites revealed a distinct NMR signal with identical chemical shits (1.05 and 2.18 ppm) as PA (a primary P. acne metabolite). The 1.05 ppm signal does not overlap with other bacteria metabolites, and its intensity increases linearly with P. acnes concentration. Bovine disks injected with P. acnes bacteria revealed a very distinct NMR signal at 1.05 ppm, which linearly increased with P. acnes concentration. The 1.05 ppm NMR signal from PA can be used as a marker of P. acnes infection of discs. This signal does not overlap with other disc metabolites and linearly depends on P. acnes concentration. Consequently, NMR spectroscopy may provide a noninvasive method to detect disc infection in the clinical setting. N/A.