Acquisition Efficiency and Technical Repeatability of Dual-Frequency 3D Vector MR Elastography of the Liver.

BACKGROUND: MR elastography (MRE) at 60 Hz is widely used for staging liver fibrosis. MRE with lower frequencies may provide inflammation biomarkers. PURPOSE: To establish a practical simultaneous dual-frequency liver MRE protocol at both 30 Hz and 60 Hz during a single examination and validate the occurrence of second harmonic waves at 30 Hz. STUDY TYPE: Retrospective. SUBJECTS: One hundred six patients (48 females, age: 50.0 ± 13.4 years) were divided as follows: Cohort One (15 patients with chronic liver disease [CLD] and 25 healthy volunteers) with simultaneous dual-frequency MRE. Cohort Two (66 patients with CLD) with second harmonic MRE. FIELD STRENGTH/SEQUENCE: 3-T, single- or dual-frequency MRE at 30 Hz and 60 Hz. ASSESSMENT: Liver stiffness (LS) in both cohorts was evaluated with manually placed volumetric ROIs by two independent analyzers. Image quality was assessed by three independent readers on a 4-point scale (0-3: none/failed, fair, moderate, excellent) based on the depth of wave propagation with 1/3 incremental penetration. The success rate was derived from the percentage of nonzero quality scores. STATISTICAL TESTS: Measurement agreement, bias, and repeatability of LS were assessed using intraclass correlation coefficients (ICCs), Bland-Altman plots, and repeatability coefficient (RC). Mann-Whitney U tests were used to evaluate the differences in image quality between different methods. A P-value <0.05 was considered statistically significant. RESULTS: Success rate was 97.5% in Cohort One and 91% success rate for the second harmonic MRE in Cohort Two. The second harmonic and conventional MRE showed excellent agreement in LS (all ICCs >0.90). The quality scores for the second harmonic wave images were lower than those from the conventional MRE (Z = -4.523). DATA CONCLUSION: Compared with conventional and second harmonic methods, simultaneous dual-frequency had better image quality, high success rate and the advantage of intrinsic co-registration, while the second harmonic method can be an alternative if custom waveform is not available. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 1.

Occupational exposure to solar ultraviolet radiation in an eastern North Carolina university outdoor setting during the four seasons.

Outdoor workers perform tasks throughout the year that expose them to solar ultraviolet radiation (UVR) and increase their risk of UVR-related adverse health effects. Multiple studies on occupational solar UVR exposures during summer have been published but similar investigations during other seasons are limited. The purpose of this study was to assess solar UVR exposure in an eastern North Carolina university setting during all four seasons (fall, winter, spring, and summer) to assess risk for outdoor workers, particularly groundskeepers, throughout the year. UVR effective irradiance (UVReff) was measured by area monitoring using a digital data-logging radiometer and a weatherproof UVR detector for 164 days from October 2020 to October 2021. Results showed that hourly and daily mean UVReff exceeded the 1-hr and 8-hr ACGIH Threshold Limit Values (TLVs), respectively, in all months and seasons at varying degrees. Winter had the lowest mean UVReff (3.4 × 10-3 ± 1.7 × 10-3 mW/cm2), but 91.1% and 100% of the hourly and daily UVReff measurements, respectively, still exceeded the TLVs. This study demonstrates the risk of overexposure to solar UVR among outdoor workers during cold months and seasons and the importance of implementing UVR protection throughout the year.

Abdominal MR elastography with multiple driver arrays: performance and repeatability.

PURPOSE: To evaluate the performance and repeatability assessing liver, spleen, and kidney stiffness with magnetic resonance elastography (MRE), using arrays of pneumatic passive drivers. METHODS: An array of four flexible, pneumatically activated passive drivers for abdominal MRE were developed and tested in this study. Multiple MRE acquisitions were performed prospectively in a series of eleven volunteers, with activation of all combinations of the four drivers, individually and simultaneously. MRE exams were repeated three times to study within-day and between-day test-retest repeatability. Semi-quantitative evaluation of wave propagation and penetration, and quantitative assessment of tissue stiffness was conducted for liver, spleen, and kidneys. RESULTS: When driver location and amplitude were sufficient to achieve necessary shear wave illumination in any given region of interest, the results showed excellent test-retest repeatability in abdominal organ stiffness with both single and multiple driver configurations. The results confirmed that multiple driver arrays provided suitable shear wave illumination over a larger region of the abdomen, allowing more reliable stiffness measurements in multiple organs. MRE assessment of the spleen was found to be prone to effects of excessive shear wave amplitude, however. CONCLUSION: A multiple driver array provides shear wave illumination over a larger region of the abdomen than obtained with a single driver, for MRE assessment of multiple abdominal organs, providing excellent test-retest repeatability in stiffness measurements. However, careful tuning of the location and amplitude of each driver is essential to achieve consistent results.

Psychometrically Equivalent Fante Speech Recognition Threshold Materials by a Female Talker.

PURPOSE: This study aimed to create and evaluate digitally recorded speech materials for speech recognition threshold (SRT) testing among children and adults in Fante. Fifty-one (51) familiar trisyllabic words were chosen from a list of 107 widely used trisyllabic Fante words. They were digitally captured and edited to create the same root mean square as a 1-kHz calibration tone. METHOD: The study used a three-phase cross-sectional study method. Twenty native Fante speakers with normal hearing thresholds were selected at random for listener evaluation. For each of the words, the researchers used logistic regression to measure the slope, intercepts, and psychometric function slope at 50% and from 20% to 80%. In the study, the intensity of each word was modified digitally, so that the threshold at 50% of each word was equal to the mean pure-tone average (PTA) of the participants to increase the homogeneity of the thresholds of the selected words. RESULTS: A final list of 25 familiar homogenous words with the same tone patterns of slopes greater than 7%/dB was finally selected and recorded for speech audiometry in Fante. CONCLUSIONS: Psychometrically equivalent trisyllabic words in Fante were successfully developed and evaluated for SRT testing in Ghana. There is a need for the development of speech audiometry materials in other Ghanaian languages.

Biophysical Evaluation of Rhesus Macaque Fc Gamma Receptors Reveals Similar IgG Fc Glycoform Preferences to Human Receptors.

Rhesus macaques are a common non-human primate model used in the evaluation of human monoclonal antibodies, molecules whose effector functions depend on a conserved N-linked glycan in the Fc region. This carbohydrate is a target of glycoengineering efforts aimed at altering antibody effector function by modulating the affinity of Fcγ receptors. For example, a reduction in the overall core fucose content is one such strategy that can increase antibody-mediated cellular cytotoxicity by increasing Fc-FcγRIIIa affinity. While the position of the Fc glycan is conserved in macaques, differences in the frequency of glycoforms and the use of an alternate monosaccharide in sialylated glycan species add a degree of uncertainty to the testing of glycoengineered human antibodies in rhesus macaques. Using a panel of 16 human IgG1 glycovariants, we measured the affinities of macaque FcγRs for differing glycoforms via surface plasmon resonance. Our results suggest that macaques are a tractable species in which to test the effects of antibody glycoengineering.

Factors influencing daily quality assurance measurements of magnetic resonance imaging scanners.

Magnetic resonance imaging is commonly used in hospitals and clinics to aid medical diagnoses. Scanner performance should be assessed regularly, including daily, weekly, and yearly evaluations to ensure high-quality and artifact-free images. Of these assessments, the daily quality assurance monitors the image quality of the scanner using a manufacturer-provided protocol. In this study, we sought to determine the factors that introduced variability in daily quality assurance data. A phantom was scanned using a head coil in two schemes: with varied phantom placement daily, and with a single phantom placement, and evaluated over approximately 1 month. Minor placement and localization changes accounted for approximately 50% of the variability in the signal-to-noise ratios observed in these measures, driven by changes in the measured signal, while the noise remained constant. The changes in the signal-to-noise ratios were small over the 2-month study period.

Industrial hemp as an agricultural crop in Ghana.

BACKGROUND: Cannabis is one of humanity's oldest crops with several uses, from food to clothing and medicine. It remains one of the most controversial crops whose production, possession, and usage are regulated differently across jurisdictions. Academic research and advocacy have resulted in the redefinition of the legal status of cannabis in several countries. Ghana recently reviewed its laws on cannabis, allowing for the cultivation of industrial hemp. The legislation paves the way for Ghana to benefit from industrial hemp and include it in the agricultural cash crop list. This paper looks at the economic prospects of industrial hemp in the wake of the new law. METHODS: A systematic electronic research was conducted to identify journal articles, reports, news, blogs, and other relevant materials on cannabis, marijuana, and industrial hemp. The electronic search was done primarily on Google, Google Scholar, Bing, and "Baidu Xueshi" to identify cannabis-related publications. The search was expanded beyond Ghana to find other perspectives on cannabis. The search began in January 2020 on Google using search terms like "cannabis in Ghana" and "which countries have legal cannabis." Materials on history, financial prospects, industrial uses, and legislations on cannabis and industrial hemp were reviewed. RESULTS: Existing research on cannabis in Ghana has focused on the psychotic effects of cannabis other than its industrial aspects, which has potentials for the economy. Industrial hemp has CBD with no psychotic effects and is very useful in making medicine, paper, and textiles. Ghana has both the land and workforce to produce hemp to feed local industries and the international market. CONCLUSION: The new legislation can put Ghana in a position to benefit from the current cannabis industry. Therefore, policymakers should implement a registration regime that would favor local investors and farmers to reduce illegal production. The regulatory framework should establish a well-equipped agency that will supervise production and research into hemp development.

Proton Exchange Magnetic Resonance Imaging: Current and Future Applications in Psychiatric Research.

Proton exchange provides a powerful contrast mechanism for magnetic resonance imaging (MRI). MRI techniques sensitive to proton exchange provide new opportunities to map, with high spatial and temporal resolution, compounds important for brain metabolism and function. Two such techniques, chemical exchange saturation transfer (CEST) and T1 relaxation in the rotating frame (T1ρ), are emerging as promising tools in the study of neurological and psychiatric illnesses to study brain metabolism. This review describes proton exchange for non-experts, highlights the current status of proton-exchange MRI, and presents advantages and drawbacks of these techniques compared to more traditional methods of imaging brain metabolism, including positron emission tomography (PET) and MR spectroscopy (MRS). Finally, this review highlights new frontiers for the use of CEST and T1ρ in brain research.

R1ρ sensitivity to pH and other compounds at clinically accessible spin-lock fields in the presence of proteins.

Numerous human diseases involve abnormal metabolism, and proton exchange is an effective source of magnetic resonance imaging (MRI) contrast for assessing metabolism. One MRI technique that capitalizes on proton exchange is R1 relaxation in the rotating frame (R1ρ ). Here, we investigated the sensitivity of R1ρ to various proton-exchange mechanisms at spin-lock pulses within Food and Drug Administration (FDA) safety guidelines for radiofrequency-induced heating. We systematically varied pH known to change the rate of proton exchange as well as the glucose and lysine concentrations, thus changing the number of amide, hydroxyl and amine exchangeable sites in a series of egg-white albumin phantoms. The resulting effects on quantitative relaxation time measurements of R1ρ , R1 and R2 were observed at 3 T. Using spin-lock amplitudes available for human imaging (less than 23.5 µT) at near physiologic temperatures, we found R1ρ was more sensitive to physiologic changes in pH than to changes in glucose and lysine concentrations. In addition, R1ρ was more sensitive to pH changes than R1 and R2 . Models of proton exchange fitted to the relaxation measurements suggest that amide groups were the primary source of pH sensitivity. Together, these experiments suggest an optimal spin-lock amplitude for measuring pH changes while not exceeding FDA-subject heating limitations.

Enrichment of high affinity subclasses and glycoforms from serum-derived IgG using FcγRs as affinity ligands.

As antibodies continue to gain predominance in drug discovery and development pipelines, efforts to control and optimize their activity in vivo have matured to incorporate sophisticated abilities to manipulate engagement of specific Fc binding partners. Such efforts to promote diverse functional outcomes include modulating IgG-Fc affinity for FcγRs to alternatively potentiate or reduce effector functions, such as antibody-dependent cellular cytotoxicity and phagocytosis. While a number of natural and engineered Fc features capable of eliciting variable effector functions have been demonstrated in vitro and in vivo, elucidation of these important functional relationships has taken significant effort through use of diverse genetic, cellular and enzymatic techniques. As an orthogonal approach, we demonstrate use of FcγR as chromatographic affinity ligands to enrich and therefore simultaneously identify favored binding species from a complex mixture of serum-derived pooled polycloncal human IgG, a load material that contains the natural repertoire of Fc variants and post-translational modifications. The FcγR-enriched IgG was characterized for subclass and glycoform composition and the impact of this bioseparation step on antibody activity was measured in cell-based effector function assays including Natural Killer cell activation and monocyte phagocytosis. This work demonstrates a tractable means to rapidly distinguish complex functional relationships between two or more interacting biological agents by leveraging affinity chromatography followed by secondary analysis with high-resolution biophysical and functional assays and emphasizes a platform capable of surveying diverse natural post-translational modifications that may not be easily produced with high purity or easily accessible with recombinant expression techniques.

IgG Fc variant cross-reactivity between human and rhesus macaque FcγRs.

Non-human primate (NHP) studies are often an essential component of antibody development efforts before human trials. Because the efficacy or toxicity of candidate antibodies may depend on their interactions with Fcγ receptors (FcγR) and their resulting ability to induce FcγR-mediated effector functions such as antibody-dependent cell-meditated cytotoxicity and phagocytosis (ADCP), the evaluation of human IgG variants with modulated affinity toward human FcγR is becoming more prevalent in both infectious disease and oncology studies in NHP. Reliable translation of these results necessitates analysis of the cross-reactivity of these human Fc variants with NHP FcγR. We report evaluation of the binding affinities of a panel of human IgG subclasses, Fc amino acid point mutants and Fc glycosylation variants against the common allotypes of human and rhesus macaque FcγR by applying a high-throughput array-based surface plasmon resonance platform. The resulting data indicate that amino acid variation present in rhesus FcγRs can result in disrupted, matched, or even increased affinity of IgG Fc variants compared with human FcγR orthologs. These observations emphasize the importance of evaluating species cross-reactivity and developing an understanding of the potential limitations or suitability of representative in vitro and in vivo models before human clinical studies when either efficacy or toxicity may be associated with FcγR engagement.

Biophysical and Functional Characterization of Rhesus Macaque IgG Subclasses.

Antibodies raised in Indian rhesus macaques [Macaca mulatta (MM)] in many preclinical vaccine studies are often evaluated in vitro for titer, antigen-recognition breadth, neutralization potency, and/or effector function, and in vivo for potential associations with protection. However, despite reliance on this key animal model in translation of promising candidate vaccines for evaluation in first in man studies, little is known about the properties of MM immunoglobulin G (IgG) subclasses and how they may compare to human IgG subclasses. Here, we evaluate the binding of MM IgG1, IgG2, IgG3, and IgG4 to human Fc gamma receptors (FcγR) and their ability to elicit the effector functions of human FcγR-bearing cells, and unlike in humans, find a notable absence of subclasses with dramatically silent Fc regions. Biophysical, in vitro, and in vivo characterization revealed MM IgG1 exhibited the greatest effector function activity followed by IgG2 and then IgG3/4. These findings in rhesus are in contrast with the canonical understanding that IgG1 and IgG3 dominate effector function in humans, indicating that subclass-switching profiles observed in rhesus studies may not strictly recapitulate those observed in human vaccine studies.

IgG Binding Characteristics of Rhesus Macaque FcγR.

Indian rhesus macaques (Macaca mulatta) are routinely used in preclinical studies to evaluate therapeutic Abs and candidate vaccines. The efficacy of these interventions in many cases is known to rely heavily on the ability of Abs to interact with a set of Ab FcγR expressed on innate immune cells. Yet, despite their presumed functional importance, M. mulatta Ab receptors are largely uncharacterized, posing a fundamental limit to ensuring accurate interpretation and translation of results from studies in this model. In this article, we describe the binding characteristics of the most prevalent allotypic variants of M. mulatta FcγR for binding to both human and M. mulatta IgG of varying subclasses. The resulting determination of the affinity, specificity, and glycan sensitivity of these receptors promises to be useful in designing and evaluating studies of candidate vaccines and therapeutic Abs in this key animal model and exposes significant evolutionary divergence between humans and macaques.

Enhancing the Quality of Antibodies to HIV-1 Envelope by GagPol-Specific Th Cells.

The importance of Fc-dependent effector functions of Abs induced by vaccination is increasingly recognized. However, vaccination of mice against HIV envelope (Env) induced a skewed Th cell response leading to Env-specific Abs with reduced effector function. To overcome this bias, GagPol-specific Th cells were harnessed to provide intrastructural help for Env-specific B cells after immunization with virus-like particles containing GagPol and Env. This led to a balanced Env-specific humoral immune response with a more inflammatory Fc glycan profile. The increased quality in the Ab response against Env was confirmed by FcγR activation assays. Because the Env-specific Th cell response was also biased in human vaccinees, intrastructural help is an attractive novel approach to increase the efficacy of prophylactic HIV Env-based vaccines and may also be applicable to other particulate vaccines.

Microscale purification of antigen-specific antibodies.

Glycosylation of the Fc domain is an important driver of antibody effector function. While assessment of antibody glycoform compositions observed across total plasma IgG has identified differences associated with a variety of clinical conditions, in many cases it is the glycosylation state of only antibodies against a specific antigen or set of antigens that may be of interest, for example, in defining the potential effector function of antibodies produced during disease or after vaccination. Historically, glycoprofiling such antigen-specific antibodies in clinical samples has been challenging due to their low prevalence, the high sample requirement for most methods of glycan determination, and the lack of high-throughput purification methods. New methods of glycoprofiling with lower sample requirements and higher throughput have motivated the development of microscale and automatable methods for purification of antigen-specific antibodies from polyclonal sources such as clinical serum samples. In this work, we present a robot-compatible 96-well plate-based method for purification of antigen-specific antibodies, suitable for such population level glycosylation screening. We demonstrate the utility of this method across multiple antibody sources, using both purified plasma IgG and plasma, and across multiple different antigen types, with enrichment factors greater than 1000-fold observed. Using an on-column IdeS protease treatment, we further describe staged release of Fc and Fab domains, allowing for glycoprofiling of each domain.