Biogeographic response of marine plankton to Cenozoic environmental changes.

In palaeontological studies, groups with consistent ecological and morphological traits across a clade's history (functional groups)1 afford different perspectives on biodiversity dynamics than do species and genera2,3, which are evolutionarily ephemeral. Here we analyse Triton, a global dataset of Cenozoic macroperforate planktonic foraminiferal occurrences4, to contextualize changes in latitudinal equitability gradients1, functional diversity, palaeolatitudinal specialization and community equitability. We identify: global morphological communities becoming less specialized preceding the richness increase after the Cretaceous-Palaeogene extinction; ecological specialization during the Early Eocene Climatic Optimum, suggesting inhibitive equatorial temperatures during the peak of the Cenozoic hothouse; increased specialization due to circulation changes across the Eocene-Oligocene transition, preceding the loss of morphological diversity; changes in morphological specialization and richness about 19 million years ago, coeval with pelagic shark extinctions5; delayed onset of changing functional group richness and specialization between hemispheres during the mid-Miocene plankton diversification. The detailed nature of the Triton dataset permits a unique spatiotemporal view of Cenozoic pelagic macroevolution, in which global biogeographic responses of functional communities and richness are decoupled during Cenozoic climate events. The global response of functional groups to similar abiotic selection pressures may depend on the background climatic state (greenhouse or icehouse) to which a group is adapted.

Late Cenozoic cooling restructured global marine plankton communities.

The geographic ranges of marine organisms, including planktonic foraminifera1, diatoms, dinoflagellates2, copepods3 and fish4, are shifting polewards owing to anthropogenic climate change5. However, the extent to which species will move and whether these poleward range shifts represent precursor signals that lead to extinction is unclear6. Understanding the development of marine biodiversity patterns over geological time and the factors that influence them are key to contextualizing these current trends. The fossil record of the macroperforate planktonic foraminifera provides a rich and phylogenetically resolved dataset that provides unique opportunities for understanding marine biogeography dynamics and how species distributions have responded to ancient climate changes. Here we apply a bipartite network approach to quantify group diversity, latitudinal specialization and latitudinal equitability for planktonic foraminifera over the past eight million years using Triton, a recently developed high-resolution global dataset of planktonic foraminiferal occurrences7. The results depict a global, clade-wide shift towards the Equator in ecological and morphological community equitability over the past eight million years in response to temperature changes during the late Cenozoic bipolar ice sheet formation. Collectively, the Triton data indicate the presence of a latitudinal equitability gradient among planktonic foraminiferal functional groups which is coupled to the latitudinal biodiversity gradient only through the geologically recent past (the past two million years). Before this time, latitudinal equitability gradients indicate that higher latitudes promoted community equitability across ecological and morphological groups. Observed range shifts among marine planktonic microorganisms1,2,8 in the recent and geological past suggest substantial poleward expansion of marine communities even under the most conservative future global warming scenarios.

Higher-order effects, continuous species interactions, and trait evolution shape microbial spatial dynamics.

The assembly and maintenance of microbial diversity in natural communities, despite the abundance of toxin-based antagonistic interactions, presents major challenges for biological understanding. A common framework for investigating such antagonistic interactions involves cyclic dominance games with pairwise interactions. The incorporation of higher-order interactions in such models permits increased levels of microbial diversity, especially in communities in which antibiotic-producing, sensitive, and resistant strains coexist. However, most such models involve a small number of discrete species, assume a notion of pure cyclic dominance, and focus on low mutation rate regimes, none of which well represent the highly interlinked, quickly evolving, and continuous nature of microbial phenotypic space. Here, we present an alternative vision of spatial dynamics for microbial communities based on antagonistic interactions-one in which a large number of species interact in continuous phenotypic space, are capable of rapid mutation, and engage in both direct and higher-order interactions mediated by production of and resistance to antibiotics. Focusing on toxin production, vulnerability, and inhibition among species, we observe highly divergent patterns of diversity and spatial community dynamics. We find that species interaction constraints (rather than mobility) best predict spatiotemporal disturbance regimes, whereas community formation time, mobility, and mutation size best explain patterns of diversity. We also report an intriguing relationship among community formation time, spatial disturbance regimes, and diversity dynamics. This relationship, which suggests that both higher-order interactions and rapid evolution are critical for the origin and maintenance of microbial diversity, has broad-ranging links to the maintenance of diversity in other systems.

Animal soundscapes reveal key markers of Amazon forest degradation from fire and logging.

Safeguarding tropical forest biodiversity requires solutions for monitoring ecosystem structure over time. In the Amazon, logging and fire reduce forest carbon stocks and alter habitat, but the long-term consequences for wildlife remain unclear, especially for lesser-known taxa. Here, we combined multiday acoustic surveys, airborne lidar, and satellite time series covering logged and burned forests (n = 39) in the southern Brazilian Amazon to identify acoustic markers of forest degradation. Our findings contradict expectations from the Acoustic Niche Hypothesis that animal communities in more degraded habitats occupy fewer "acoustic niches" defined by time and frequency. Instead, we found that aboveground biomass was not a consistent proxy for acoustic biodiversity due to the divergent patterns of "acoustic space occupancy" between logged and burned forests. Ecosystem soundscapes highlighted a stark, and sustained reorganization in acoustic community assembly after multiple fires; animal communication networks were quieter, more homogenous, and less acoustically integrated in forests burned multiple times than in logged or once-burned forests. These findings demonstrate strong biodiversity cobenefits from protecting burned Amazon forests from recurrent fire. By contrast, soundscape changes after logging were subtle and more consistent with acoustic community recovery than reassembly. In both logged and burned forests, insects were the dominant acoustic markers of degradation, particularly during midday and nighttime hours, which are not typically sampled by traditional biodiversity field surveys. The acoustic fingerprints of degradation history were conserved across replicate recording locations, indicating that soundscapes may offer a robust, taxonomically inclusive solution for digitally tracking changes in acoustic community composition over time.

In vivo B 1 + enhancement of calf MRI at 7 T via optimized flexible metasurfaces.

PURPOSE: Ultrahigh field (≥7 T) MRI is at the cutting edge of medical imaging, enabling enhanced spatial and spectral resolution as well as enhanced susceptibility contrast. However, transmit ( B 1 + $$ {\mathrm{B}}_1^{+} $$ ) field inhomogeneity due to standing wave effects caused by the shortened RF wavelengths at 7 T is still a challenge to overcome. Novel hardware methods such as dielectric pads have been shown to improve the B 1 + $$ {\mathrm{B}}_1^{+} $$ field inhomogeneity but are currently limited in their corrective effect by the range of high-permittivity materials available and have a fixed shelf life. In this work, an optimized metasurface design is presented that demonstrates in vivo enhancement of the B 1 + $$ {\mathrm{B}}_1^{+} $$ field. METHODS: A prototype metasurface was optimized by an empirical capacitor sweep and by varying the period size. Phantom temperature experiments were performed to evaluate potential metasurface heating effects during scanning. Lastly, in vivo gradient echo images and B 1 + $$ {\mathrm{B}}_1^{+} $$ maps were acquired on five healthy subjects on a 7 T system. Dielectric pads were also used as a comparison throughout the work as a standard comparison. RESULTS: The metasurfaces presented here enhanced the average relative SNR of the gradient echo images by a factor of 2.26 compared to the dielectric pads factor of 1.61. Average B 1 + $$ {\mathrm{B}}_1^{+} $$ values reflected a similar enhancement of 27.6% with the metasurfaces present versus 8.9% with the dielectric pads. CONCLUSION: The results demonstrate that metasurfaces provide superior performance to dielectric padding as shown by B 1 + $$ {\mathrm{B}}_1^{+} $$ maps reflecting their direct effects and resulting enhancements in image SNR at 7 T.

Repeatability of Lac+ measurements in healthy human brain at 3 T.

PURPOSE: In vivo quantification of lactate has numerous applications in studying the pathology of both cerebral and musculoskeletal systems. Due to its low concentration (~0.5-1 mM), and overlap with lipid signals, traditional 1H MR spectra acquired in vivo using a small voxel and short echo time often result in an inadequate signal to detect and resolve the lactate peak, especially in healthy human volunteers. METHODS: In this study, using a semi-LASER acquisition with long echo time (TE = 288 ms) and large voxel size (80 × 70 × 20 mm3), we clearly visualize the combined signal of lactate and threonine. Therefore, we call the signal at 1.33 ppm Lac+ and quantify Lac+ concentration from water suppressed spectra in healthy human brains in vivo. Four participants (22-37 years old; mean age = 28 ± 5.4; three male, one female) were scanned on four separate days, and on each day four measurements were taken. Intra-day values are calculated for each participant by comparing the four measurements on a single day. Inter-day values were calculated using the mean intra-day measurements. RESULTS: The mean intra-participant Lac+ concentration, standard deviation (SD), and coefficient of variation (CV) ranged from 0.49 to 0.61 mM, 0.02 to 0.07 mM, and 4% to 13%, respectively, across four volunteers. The inter-participant Lac+ concentration, SD, and CV was 0.53 mM, ±0.06 mM, and 11%. CONCLUSION: Repeatability is shown in Lac+ measurement in healthy human brain using a long echo time semi-LASER sequence with a large voxel in about 3.5 min at 3 T.

Low diversity, high dominance, and high host prevalence of parasitic isopods of the family Cymothoidae in Chilika lagoon, India: a comparative study between a semi-enclosed ecosystem and its adjoining open region.

Patterns in parasite diversity are shaped by their environmental and ecological settings, and to better understand their interactions with hosts and the corresponding biology, it is crucial to understand these context-dependent patterns. To achieve this, we use cymothoid isopods, an important group of fish parasites, to test a long-standing hypothesis about parasite diversity and prevalence pattern: whether semi-enclosed water bodies allow low diversity and high prevalence of parasitic isopods. Specifically, we compare these patterns between Chilika lagoon (Odisha, India), a semi-enclosed water body, and the adjoining Odisha coast (India). Our finding reveals that the semi-enclosed Chilika lagoon has a considerably lower diversity of parasitic isopods than its adjoining open sea along the Odisha coast. Additionally, the parasitic isopod infection levels in Chilika lagoon are noticeably higher, and isopod assemblage is less even than those in coastal waters along the Odisha coast. Our results support the hypothesised association between enclosed water bodies, parasite diversity, and host prevalence and contribute to an enhanced comprehension of the ecology of parasitic isopods in distinct marine environments.

Detection of sex-specific glutamate changes in subregions of hippocampus in an early-stage Alzheimer's disease mouse model using GluCEST MRI.

INTRODUCTION: Regional glucose hypometabolism resulting in glutamate loss has been shown as one of the characteristics of Alzheimer's disease (AD). Because the impact of AD varies between the sexes, we utilized glutamate-weighted chemical exchange saturation transfer (GluCEST) magnetic resonance imaging (MRI) for high-resolution spatial mapping of cerebral glutamate and investigated subregional changes in a sex-specific manner. METHODS: Eight-month-old male and female AD mice harboring mutant amyloid precursor protein (APPNL-F/NL-F: n = 36) and wild-type (WT: n = 39) mice underwent GluCEST MRI, followed by proton magnetic resonance spectroscopy (1H-MRS) in hippocampus and thalamus/hypothalamus using 9.4T preclinical MR scanner. RESULTS: GluCEST measurements revealed significant (p ≤ 0.02) glutamate loss in the entorhinal cortex (% change ± standard error: 8.73 ± 2.12%), hippocampus (11.29 ± 2.41%), and hippocampal fimbriae (19.15 ± 2.95%) of male AD mice. A similar loss of hippocampal glutamate in male AD mice (11.22 ± 2.33%; p = 0.01) was also observed in 1H-MRS. DISCUSSIONS: GluCEST MRI detected glutamate reductions in the fimbria and entorhinal cortex of male AD mice, which was not reported previously. Resilience in female AD mice against these changes indicates an intact status of cerebral energy metabolism. HIGHLIGHTS: Glutamate levels were monitored in different brain regions of early-stage Alzheimer's disease (AD) and wild-type male and female mice using glutamate-weighted chemical exchange saturation transfer (GluCEST) magnetic resonance imaging (MRI). Male AD mice exhibited significant glutamate loss in the hippocampus, entorhinal cortex, and the fimbriae of the hippocampus. Interestingly, female AD mice did not have any glutamate loss in any brain region and should be investigated further to find the probable cause. These findings demonstrate previously unreported sex-specific glutamate changes in hippocampal sub-regions using high-resolution GluCEST MRI.

Feasibility of transient nuclear Overhauser effect imaging in brain at 7 T.

PURPOSE: The nuclear Overhauser effect (NOE) quantification from the steady-state NOE imaging suffers from multiple confounding non-NOE-specific sources, including direct saturation, magnetization transfer, and relevant chemical exchange species, and is affected by B0 and B1 + inhomogeneities. The B0 -dependent and B1 + -dependent data needed for deconvolving these confounding effects would increase the scan time substantially, leading to other issues such as patient tolerability. Here, we demonstrate the feasibility of brain lipid mapping using an easily implementable transient NOE (tNOE) approach. METHODS: This 7T study used a frequency-selective inversion pulse at a range of frequency offsets between 1.0 and 5.0 parts per million (ppm) and -5.0 and -1.0 ppm relative to bulk water peak. This was followed by a fixed/variable mixing time and then a single-shot 2D turbo FLASH readout. The feasibility of tNOE measurements is demonstrated on bovine serum albumin phantoms and healthy human brains. RESULTS: The tNOE measurements from bovine serum albumin phantoms were found to be independent of physiological pH variations. Both bovine serum albumin phantoms and human brains showed broad tNOE contributions centered at approximately -3.5 ppm relative to water peak, with presumably aliphatic moieties in lipids and proteins being the dominant contributors. Less prominent tNOE contributions of approximately +2.5 ppm relative to water, presumably from aromatic moieties, were also detected. These aromatic signals were free from any CEST signals. CONCLUSION: In this study, we have demonstrated the feasibility of tNOE in human brain at 7 T. This method is more scan-time efficient than steady-state NOE and provides NOE measurement with minimal confounders.

Identification of new resonances in downfield 1 H MRS of human calf muscle in vivo: Potentially metabolite precursors for skeletal muscle NAD.

PURPOSE: The purpose of this study was to identify and characterize newly discovered resonances appearing in the downfield proton MR spectrum (DF 1 H MRS) of the human calf muscle in vivo at 7T. METHODS: Downfield 1 H MRS was performed on the calf muscle of five healthy volunteers at 7T. A spectrally selective 90° E-BURP RF pulse with an excitation center frequency at 10.3 ppm and an excitation bandwidth of 2 ppm was used for DF 1 H MRS acquisition. RESULTS: In all participants, we observed new resonances at 9.7, 10.1, 10.3, and 10.9 ppm in the DF 1 H MRS. Phantom experiments at 37°C strongly suggest the new resonance at 9.7 ppm could be from H2-proton of the nicotinamide rings in nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) while the resonance at 10.1 ppm could be attributed to the indole -NH proton of L-tryptophan. We observed that the resonances at 10.1 and 10.9 ppm are significantly suppressed when the water resonance is saturated, indicating that these peaks have either 1 H chemical exchange or cross-relaxation with water. Conversely, the resonances at 9.7 and 10.3 ppm exhibit moderate signal reduction in the presence of water saturation. CONCLUSION: We have identified new proton resonances in vivo in human calf muscle occurring at chemical shifts of 9.7, 10.1, 10.3, and 10.9 ppm. These preliminary results are promising for investigating the role of NR/NMN and L-tryptophan metabolism in understanding the de novo and salvage pathways of NAD+ synthesis in skeletal muscle.

In vivo reproducibility of 3D relayed NOE in the healthy human brain at 7 T.

PURPOSE: Nuclear Overhauser effect (NOE) is based on dipolar cross-relaxation mechanism that enables the indirect detection of aliphatic protons via the water proton signal. This work focuses on determining the reproducibility of NOE magnetization transfer ratio (NOEMTR ) and isolated or relayed NOE (rNOE) contributions to the NOE MRI of the healthy human brain at 7 Tesla (T). METHODS: We optimized the B 1 + $$ {\mathrm{B}}_1^{+} $$ amplitude and length of the saturation pulse by acquiring NOE images with different B 1 + $$ {\mathrm{B}}_1^{+} $$ values with multiple saturation lengths. Repeated NOE MRI measurements were made on five healthy volunteers by using optimized saturation pulse parameters including correction of B0 and B 1 + $$ {\mathrm{B}}_1^{+} $$ inhomogeneities. To isolate the individual contributions from z-spectra, we have fit the NOE z-spectra using multiple Lorentzians and calculated the total contribution from each pool contributing to the overall NOEMTR contrast. RESULTS: We found that a saturation amplitude of 0.72 µT and a length of 3 s provided the highest contrast. We found that the mean NOEMTR value in gray matter (GM) was 26%, and in white matter (WM) was 33.3% across the 3D slab of the brain. The mean rNOE contributions from GM and WM values were 8.9% and 9.6%, which were ∼10% of the corresponding total NOEMTR signal. The intersubject coefficient of variations (CoVs) of NOEMTR from GM and WM were 4.5% and 6.5%, respectively, whereas the CoVs of rNOE were 4.8% and 5.6%, respectively. The intrasubject CoVs of the NOEMTR range was 2.1%-4.2%, and rNOE range was 2.9%-10.5%. CONCLUSION: This work has demonstrated an excellent reproducibility of both inter- and intrasubject NOEMTR and rNOE metrics in healthy human brains at 7 T.

In vivo assessment of ß-hydroxybutyrate metabolism in mouse brain using deuterium (2 H) MRS.

PURPOSE: To monitor the metabolic turnover of ß-hydroxybutyrate (BHB) oxidation using 2 H-MRS in conjunction with intravenous administration of 2 H labeled BHB. METHODS: Nine-month-old mice were infused with [3,4,4,4]-2 H4 -BHB (d4 -BHB; 3.11 g/kg) through the tail vein using a bolus variable infusion rate for a period of 90 min. The labeling of downstream cerebral metabolites from the oxidative metabolism of d4 -BHB was monitored using 2 H-MRS spectra acquired with a home-built 2 H surface coil on a 9.4T preclinical MR scanner with a temporal resolution of 6.25 min. An exponential model was fit to the BHB and glutamate/glutamine (Glx) turnover curves to determine rate constants of metabolite turnover and to aid in the visualization of metabolite time courses. RESULTS: Deuterium label was incorporated into Glx from BHB metabolism through the tricarboxylic acid (TCA) cycle, with an increase in the level of [4,4]-2 H2 -Glx (d2 -Glx) over time and reaching a quasi-steady state concentration of ∼0.6 ± 0.1 mM following 30 min of infusion. Complete oxidative metabolic breakdown of d4 -BHB also resulted in the formation of semi-heavy water (HDO), with a four-fold (10.1 to ∼42.1 ± 7.3 mM) linear (R2  = 0.998) increase in its concentration by the end of infusion. The rate constant of Glx turnover from d4 -BHB metabolism was determined to be 0.034 ± 0.004 min-1 . CONCLUSION: 2 H-MRS can be used to monitor the cerebral metabolism of BHB with its deuterated form by measuring the downstream labeling of Glx. The integration of 2 H-MRS with deuterated BHB substrate provides an alternative and clinically promising MRS tool to detect neurometabolic fluxes in healthy and disease conditions.

B 1 + $$ {\mathrm{B}}_1

PURPOSE: Nuclear Overhauser effect magnetization transfer ratio (NOEMTR ) is a technique used to investigate brain lipids and macromolecules in greater detail than other techniques and benefits from increased contrast at 7 T. However, this contrast can become degraded because of B 1 + $$ {\mathrm{B}}_1^{+} $$ inhomogeneities present at ultra-high field strengths. High-permittivity dielectric pads (DP) have been used to correct for these inhomogeneities via displacement currents generating secondary magnetic fields. The purpose of this work is to demonstrate that dielectric pads can be used to mitigate B 1 + $$ {\mathrm{B}}_1^{+} $$ inhomogeneities and improve NOEMTR contrast in the temporal lobes at 7 T. METHODS: Partial 3D NOEMTR contrast images and whole brain B 1 + $$ {\mathrm{B}}_1^{+} $$ field maps were acquired on a 7 T MRI across six healthy subjects. Calcium titanate DP, having a relative permittivity of 110, was placed next to the subject's head near the temporal lobes. Pad corrected NOEMTR images had a separate postprocessing linear correction applied. RESULTS: DP provided supplemental B 1 + $$ {\mathrm{B}}_1^{+} $$ to the temporal lobes while also reducing the B 1 + $$ {\mathrm{B}}_1^{+} $$ magnitude across the posterior and superior regions of the brain. This resulted in a statistically significant increase in NOEMTR contrast in substructures of the temporal lobes both with and without linear correction. The padding also produced a convergence in NOEMTR contrast toward approximately equal mean values. CONCLUSION: NOEMTR images showed significant improvement in temporal lobe contrast when DP were used, which resulted from an increase in B 1 + $$ {\mathrm{B}}_1^{+} $$ homogeneity across the entire brain slab. DP-derived improvements in NOEMTR are expected to increase the robustness of the brain substructural measures both in healthy and pathological conditions.

Endophytic ancestors of modern leaf miners may have evolved in the Late Carboniferous.

Endophytic feeding behaviors, including stem borings and galling, have been observed in the fossil record from as early as the Devonian and involve the consumption of a variety of plant (and fungal) tissues. Historically, the exploitation of internal stem tissues through galling has been well documented as emerging during the Pennsylvanian (c. 323-299 million years ago (Ma)), replaced during the Permian by galling of foliar tissues. However, leaf mining, a foliar endophytic behavior that today is exhibited exclusively by members of the four hyperdiverse holometabolous insect orders, has been more sparsely documented, with confirmed examples dating back only to the Early Triassic (c. 252-250 Ma). Here, we describe a trace fossil on seed-fern foliage from the Rhode Island Formation of Massachusetts, USA, representing the earliest indication of a general, endophytic type of feeding damage and dating from the Middle Pennsylvanian (c. 312 Ma). Although lacking the full features of Mesozoic leaf mines, this specimen provides evidence of how endophytic mining behavior may have originated. It sheds light on the evolutionary transition to true foliar endophagy, contributes to our understanding of the behaviors of early holometabolous insects, and enhances our knowledge of macroevolutionary patterns of plant-insect interactions.

Integrating 1H MRS and deuterium labeled glucose for mapping the dynamics of neural metabolism in humans.

In the technique presented here, dubbed 'qMRS', we quantify the change in 1H MRS signal following administration of 2H-labeled glucose. As in recent human DMRS studies, we administer [6,6'-2H2]-glucose orally to healthy subjects. Since 2H is not detectable by 1H MRS, the transfer of the 2H label from glucose to a downstream metabolite leads to a reduction in the corresponding 1H MRS resonance of the metabolite, even if the total concentration of both isoforms remains constant. Moreover, introduction of the deuterium label alters the splitting pattern of the proton resonances, making indirect detection of the deuterated forms- as well as the direct detection of the decrease in unlabeled form- possible even without a 2H coil. Because qMRS requires only standard 1H MRS acquisition methods, it can be performed using commonly implemented single voxel spectroscopy (SVS) and chemical shift imaging (CSI) sequences. In this work, we implement qMRS in semi-LASER based CSI, generating dynamic maps arising from the fitted spectra, and demonstrating the feasibility of using qMRS and qCSI to monitor dynamic metabolism in the human brain using a 7T scanner with no auxiliary hardware.

Identification of l-Tryptophan by down-field 1 H MRS: A precursor for brain NAD+ and serotonin syntheses.

PURPOSE: To explore the presence of new resonances beyond 9.4 ppm from the human brain, down-field proton MRS was performed in vivo in the human brain on 6 healthy volunteers at 7 T. METHODS: To maximize the SNR, a large voxel was placed within the brain to cover the maximal area in such a way that sinus cavities were avoided. A spectrally selective 90° E-BURP pulse with an excitation bandwidth of 2 ppm was used to probe the spectral chemical shift range between 9.1 and 10.5 ppm. The E-BURP pulse was integrated with PRESS spatial localization to obtain non-water-suppressed proton MR spectra from the desired spectral region. RESULTS: In the down-field proton MRS obtained from all of the volunteers scanned, we identified a new peak consistently resonating at 10.1 ppm. Protons associated with this resonance are in cross-relaxation with the bulk water, as demonstrated by the water saturation and deuterium exchange experiments. CONCLUSION: Based on the chemical shift, this new peak was identified as the indole (-NH) proton of l-tryptophan (l-TRP) and was further confirmed from phantom experiments on l-TRP. These promising preliminary results potentially pave the way to investigate the role of cerebral metabolism of l-TRP in healthy and disease conditions.

In vitro trackable assembly of RNA-specific nucleocapsids of the respiratory syncytial virus.

The templates for transcription and replication by respiratory syncytial virus (RSV) polymerase are helical nucleocapsids (NCs), formed by viral RNAs that are encapsidated by the nucleoprotein (N). Proper NC assembly is vital for RSV polymerase to engage the RNA template for RNA synthesis. Previous studies of NCs or nucleocapsid-like particles (NCLPs) from RSV and other nonsegmented negative-sense RNA viruses have provided insights into the overall NC architecture. However, in these studies, the RNAs were either random cellular RNAs or average viral genomic RNAs. An in-depth mechanistic understanding of NCs has been hampered by lack of an in vitro assay that can track NC or NCLP assembly. Here we established a protocol to obtain RNA-free N protein (N0) and successfully demonstrated the utility of a new assay for tracking assembly of N with RNA oligonucleotides into NCLPs. We discovered that the efficiency of the NCLP (N-RNA) assembly depends on the length and sequence of the RNA incorporated into NCLPs. This work provides a framework to generate purified N0 and incorporate it with RNA into NCLPs in a controllable manner. We anticipate that our assay for in vitro trackable assembly of RSV-specific nucleocapsids may enable in-depth mechanistic analyses of this process.

Multi-component T2∗ relaxation modelling in human Achilles tendon: Quantifying chemical shift information in ultra-short echo time imaging.

PURPOSE: To examine multi-component relaxation modelling for quantification of on- and off-resonance relaxation signals in multi-echo ultra-short echo time (UTE) data of human Achilles tendon (AT) and compare bias and dispersion errors of model parameters to that of the bi-component model. THEORY AND METHODS: Multi-component modelling is demonstrated for quantitative multi-echo UTE analysis of AT and supported using a novel method for determining number of MR-visible off-resonance components, UTE data from six healthy volunteers, and analysis of proton NMR measurements from ex vivo bovine AT. Cramer-Rao lower bound expressions are presented for multi- and bi-component models and parameter estimate variances are compared. Bias error in bi-component estimates is characterized numerically. RESULTS: Two off-resonance components were consistently detected in all six volunteers and in bovine AT data. Multi-component model exhibited superior quality of fit, with a marginal increase in estimate variance, when compared to the bi-component model. Bi-component estimates exhibited notable bias particularly in R2,1∗ in the presence of off-resonance components. CONCLUSION: Multi-component modelling more reliably quantifies tendon matrix water components while also providing quantitation of additional non-water matrix constituents. Further work is needed to interpret the origin of the observed off-resonance signals with preliminary assignments made to chemical groups in lipids and proteoglycans.

Niche partitioning and host specialisation in fish-parasitising isopods: Trait-dependent patterns from three ecosystems on the east coast of India.

Due to their large size and obligate nature, Cymothoid isopods inflict a high degree of tissue damage to fish. Still, they are understudied at an ecosystem level despite their global presence and ecological role. In this work, we collected fish host-isopod parasite data, along with their life history and ecological traits, from the northern part of the east coast of India and investigated patterns in host specialisation and preference of isopod parasites using a trait-based network perspective. We observed that the region of attachment of the parasite (buccal cavity, branchial cavity, and skin) and host fish ecology (schooling behaviour and habitat characteristics) influenced host specialisation and preference. We found that branchial cavity-attaching parasites preferred schooling, pelagic fishes, whereas buccal cavity-attaching parasites preferred mostly non-schooling, demersal fishes. Skin-attaching parasites were found to be generalists and had no preference based on our examined host traits.