Hot off the Press.

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as eugeniinaline A from Leuconotis eugeniifolia.

Evaluation of toothpastes for treating root carious lesions - a laboratory-based pilot study.

BACKGROUND: Root caries is preventable and can be arrested at any stage of disease development. The aim of this study was to investigate the potential mineral exchange and fluorapatite formation within artificial root carious lesions (ARCLs) using different toothpastes containing 5,000 ppm F, 1,450 ppm F or bioactive glass (BG) with 540 ppm F. MATERIALS AND METHODS: The crowns of each extracted sound tooth were removed. The remaining roots were divided into four parts (n = 12). Each sample was randomly allocated into one of four groups: Group 1 (Deionised water); Group 2 (BG with 540 ppm F); Group 3 (1,450 ppm F) and Group 4 (5,000 ppm F). ARCLs were developed using demineralisation solution (pH 4.8). The samples were then pH-cycled in 13 days using demineralisation solution (6 h) and remineralisation solution (pH 7) (16 h). Standard tooth brushing was carried out twice a day with the assigned toothpaste. X-ray Microtomography (XMT) was performed for each sample at baseline, following ARCL formation and after 13-day pH-cycling. Scanning Electron Microscope (SEM) and 19F Magic angle spinning nuclear magnetic resonance (19F-MAS-NMR) were also performed. RESULTS: XMT results showed that the highest mineral content increase (mean ± SD) was Group 4 (0.09 ± 0.05), whilst the mineral content decreased in Group 1 (-0.08 ± 0.06) after 13-day pH-cycling, however there was evidence of mineral loss within the subsurface for Groups 1, 3 and 4 (p < 0.05). SEM scans showed that mineral contents within the surface of dentine tubules were high in comparison to the subsurface in all toothpaste groups. There was evidence of dentine tubules being either partially or completely occluded in toothpaste groups. 19F-MAS-NMR showed peaks between - 103 and - 104ppm corresponding to fluorapatite formation in Groups 3 and 4. CONCLUSION: Within the limitation of this laboratory-based study, all toothpastes were potentially effective to increase the mineral density of artificial root caries on the surface, however there was evidence of mineral loss within the subsurface for Groups 1, 3 and 4.

Oligodendrocyte Maturation Alters the Cell Death Mechanisms That Cause Demyelination.

Myelinating oligodendrocytes die in human disease and early in aging. Despite this, the mechanisms that underly oligodendrocyte death are not resolved and it is also not clear whether these mechanisms change as oligodendrocyte lineage cells are undergoing differentiation and maturation. Here, we used a combination of intravital imaging, single-cell ablation, and cuprizone-mediated demyelination, in both female and male mice, to discover that oligodendrocyte maturation dictates the dynamics and mechanisms of cell death. After single-cell phototoxic damage, oligodendrocyte precursor cells underwent programmed cell death within hours, differentiating oligodendrocytes died over several days, while mature oligodendrocytes took weeks to die. Importantly cells at each maturation stage all eventually died but did so with drastically different temporal dynamics and morphological features. Consistent with this, cuprizone treatment initiated a caspase-3-dependent form of rapid cell death in differentiating oligodendrocytes, while mature oligodendrocytes never activated this executioner caspase. Instead, mature oligodendrocytes exhibited delayed cell death which was marked by DNA damage and disruption in poly-ADP-ribose subcellular localization. Thus, oligodendrocyte maturation plays a key role in determining the mechanism of death a cell undergoes in response to the same insult. This means that oligodendrocyte maturation is important to consider when designing strategies for preventing cell death and preserving myelin while also enhancing the survival of new oligodendrocytes in demyelinating conditions.

Bioactive glass-ceramics containing fluorapatite, xonotlite, cuspidine and wollastonite form apatite faster than their corresponding glasses.

Crystallisation of bioactive glasses has been claimed to negatively affect the ion release from bioactive glasses. Here, we compare ion release and mineralisation in Tris-HCl buffer solution for a series of glass-ceramics and their parent glasses in the system SiO2-CaO-P2O5-CaF2. Time-resolved X-ray diffraction analysis of glass-ceramic degradation, including quantification of crystal fractions by full pattern refinement, show that the glass-ceramics precipitated apatite faster than the corresponding glasses, in agreement with faster ion release from the glass-ceramics. Imaging by transmission electron microscopy and X-ray nano-computed tomography suggest that this accelerated degradation may be caused by the presence of nano-sized channels along the internal crystal/glassy matrix interfaces. In addition, the presence of crystalline fluorapatite in the glass-ceramics facilitated apatite nucleation and crystallisation during immersion. These results suggest that the popular view of bioactive glass crystallisation being a disadvantage for degradation, apatite formation and, subsequently, bioactivity may depend on the actual system study and, thus, has to be reconsidered.

Hot off the press.

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as dcalycinumine A from Daphniphyllum calycinum.

Correction: Hot off the Press.

Correction for 'Hot off the Press' by Robert A. Hill et al., Nat. Prod. Rep., 2023, 40, 1816-1821, https://doi.org/10.1039/d3np90052e.

UBR5 promotes antiviral immunity by disengaging the transcriptional brake on RIG-I like receptors.

The Retinoic acid-Inducible Gene I (RIG-I) like receptors (RLRs) are the major viral RNA sensors essential for the initiation of antiviral immune responses. RLRs are subjected to stringent transcriptional and posttranslational regulations, of which ubiquitination is one of the most important. However, the role of ubiquitination in RLR transcription is unknown. Here, we screen 375 definite ubiquitin ligase knockout cell lines and identify Ubiquitin Protein Ligase E3 Component N-Recognin 5 (UBR5) as a positive regulator of RLR transcription. UBR5 deficiency reduces antiviral immune responses to RNA viruses, while increases viral replication in primary cells and mice. Ubr5 knockout mice are more susceptible to lethal RNA virus infection than wild type littermates. Mechanistically, UBR5 mediates the Lysine 63-linked ubiquitination of Tripartite Motif Protein 28 (TRIM28), an epigenetic repressor of RLRs. This modification prevents intramolecular SUMOylation of TRIM28, thus disengages the TRIM28-imposed brake on RLR transcription. In sum, UBR5 enables rapid upregulation of RLR expression to boost antiviral immune responses by ubiquitinating and de-SUMOylating TRIM28.

Nitrogen isotopes reveal independent origins of N2-fixing symbiosis in extant cycad lineages.

Cycads are ancient seed plants (gymnosperms) that emerged by the early Permian. Although they were common understory flora and food for dinosaurs in the Mesozoic, their abundance declined markedly in the Cenozoic. Extant cycads persist in restricted populations in tropical and subtropical habitats and, with their conserved morphology, are often called 'living fossils.' All surviving taxa receive nitrogen from symbiotic N2-fixing cyanobacteria living in modified roots, suggesting an ancestral origin of this symbiosis. However, such an ancient acquisition is discordant with the abundance of cycads in Mesozoic fossil assemblages, as modern N2-fixing symbioses typically occur only in nutrient-poor habitats where advantageous for survival. Here, we use foliar nitrogen isotope ratios-a proxy for N2 fixation in modern plants-to probe the antiquity of the cycad-cyanobacterial symbiosis. We find that fossilized cycad leaves from two Cenozoic representatives of extant genera have nitrogen isotopic compositions consistent with microbial N2 fixation. In contrast, all extinct cycad genera have nitrogen isotope ratios that are indistinguishable from co-existing non-cycad plants and generally inconsistent with microbial N2 fixation, pointing to nitrogen assimilation from soils and not through symbiosis. This pattern indicates that, rather than being ancestral within cycads, N2-fixing symbiosis arose independently in the lineages leading to living cycads during or after the Jurassic. The preferential survival of these lineages may therefore reflect the effects of competition with angiosperms and Cenozoic climatic change.

Features, Fates, and Functions of Oligodendrocyte Precursor Cells.

Oligodendrocyte precursor cells (OPCs) are a central nervous system resident population of glia with a distinct molecular identity and an ever-increasing list of functions. OPCs generate oligodendrocytes throughout development and across the life span in most regions of the brain and spinal cord. This process involves a complex coordination of molecular checkpoints and biophysical cues from the environment that initiate the differentiation and integration of new oligodendrocytes that synthesize myelin sheaths on axons. Outside of their progenitor role, OPCs have been proposed to play other functions including the modulation of axonal and synaptic development and the participation in bidirectional signaling with neurons and other glia. Here, we review OPC identity and known functions and discuss recent findings implying other roles for these glial cells in brain physiology and pathology.

Hot off the Press.

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as alscholarine A from Alstonia scholaris.

Mitochondrial network reorganization and transient expansion during oligodendrocyte generation.

Oligodendrocyte precursor cells (OPCs) give rise to myelinating oligodendrocytes of the central nervous system. This process persists throughout life and is essential for recovery from neurodegeneration. To better understand the cellular checkpoints that occur during oligodendrogenesis, we determined the mitochondrial distribution and morphometrics across the oligodendrocyte lineage in mouse and human cerebral cortex. During oligodendrocyte generation, mitochondrial content expanded concurrently with a change in subcellular partitioning towards the distal processes. These changes were followed by an abrupt loss of mitochondria in the oligodendrocyte processes and myelin, coinciding with sheath compaction. This reorganization and extensive expansion and depletion took 3 days. Oligodendrocyte mitochondria were stationary over days while OPC mitochondrial motility was modulated by animal arousal state within minutes. Aged OPCs also displayed decreased mitochondrial size, content, and motility. Thus, mitochondrial dynamics are linked to oligodendrocyte generation, dynamically modified by their local microenvironment, and altered in the aging brain.

Detailed Seed Cone Morpho-Anatomy Provides New Insights into Seed Cone Origin and Evolution of Podocarpaceae; Podocarpoid and Dacrydioid Clades.

The study of reproductive morphology and trait evolution provides a vital insight to understand the evolutionary history of plants. The conifer family Podocarpaceae has a remarkable diversity of seed cones, with distinct morphology among the genera and with conifers in general. However, we lack a good understanding of the seed cone morpho-anatomy and trait evolution of Podocarpaceae. We investigated detailed seed cone morpho-anatomy using staining and sectioning techniques to clarify the anatomical, morphological diversity and evolution of functional traits. The presence of a fleshy receptaculum is a characteristic feature of both clades. However, species of Retrophyllum, Afrocarpus and some species of Nageia and Podocarpus form a fleshy sarcotesta-like seed coat, lacking a fleshy receptaculum. The ancestral state reconstructions show a shift between and sometimes within the genus. Although both clades demonstrate fleshiness as an ancestral trait, the shift in fleshy structures provides evidence for complex multiple evolutions of fleshy morphologies. These seed cone traits (e.g., fleshiness and size), along with the broad, flattened and well-adapted (leaf dimorphism) foliage in both clades, are largely congruent with efficient light harvesting and bird dispersal. These traits make these two clades well adapted to their environment, when growing in communities including tall and broad-leaved angiosperms (closed-canopy angiosperm forests), compared to other podocarps, making them more successful in achieving a wider distribution and species richness.

Cell lineage analysis with somatic mutations reveals late divergence of neuronal cell types and cortical areas in human cerebral cortex.

The mammalian cerebral cortex shows functional specialization into regions with distinct neuronal compositions, most strikingly in the human brain, but little is known in about how cellular lineages shape cortical regional variation and neuronal cell types during development. Here, we use somatic single nucleotide variants (sSNVs) to map lineages of neuronal sub-types and cortical regions. Early-occurring sSNVs rarely respect Brodmann area (BA) borders, while late-occurring sSNVs mark neuron-generating clones with modest regional restriction, though descendants often dispersed into neighboring BAs. Nevertheless, in visual cortex, BA17 contains 30-70% more sSNVs compared to the neighboring BA18, with clones across the BA17/18 border distributed asymmetrically and thus displaying different cortex-wide dispersion patterns. Moreover, we find that excitatory neuron-generating clones with modest regional restriction consistently share low-mosaic sSNVs with some inhibitory neurons, suggesting significant co-generation of excitatory and some inhibitory neurons in the dorsal cortex. Our analysis reveals human-specific cortical cell lineage patterns, with both regional inhomogeneities in progenitor proliferation and late divergence of excitatory/inhibitory lineages.

Teaching and Learning Neuroanatomy with Gestures: A Description of Two Simple Hand Models.

Neuroanatomy ranks highly among the most difficult topics to master in medical school. We describe two gesture-based techniques aimed at simplifying the anatomy of two complex intracranial nervous structures: the trigeminal nerve and the cerebral fornix.

Preserving root stem cell functionality under low oxygen stress: the role of nitric oxide and phytoglobins.

MAIN CONCLUSION: The preservation of quiescent center stem cell integrity in hypoxic roots by phytoglobins is exercised through their ability to scavenge nitric oxide and attenuate its effects on auxin transport and cell degradation. Under low oxygen stress, the retention or induction of phytoglobin expression maintains cell viability while loss or lack of induction of phytoglobin leads to cell degradation. Plants have evolved unique attributes to ensure survival in the environment in which they must exist. Common among the attributes is the ability to maintain stem cells in a quiescent (or low proliferation) state in unfriendly environments. From the seed embryo to meristematic regions of the plant, quiescent stem cells exist to regenerate the organism when environmental conditions are suitable to allow plant survival. Frequently, plants dispose of mature cells or organs in the process of acclimating to the stresses to ensure survival of meristems, the stem cells of which are capable of regenerating cells and organs that have been sacrificed, a feature not generally available to mammals. Most of the research on plant stress responses has dealt with how mature cells respond because of the difficulty of specifically examining plant meristem responses to stress. This raises the question as to whether quiescent stem cells behave in a similar fashion to mature cells in their response to stress and what factors within these critical cells determine whether they survive or degrade when exposed to environmental stress. This review attempts to examine this question with respect to the quiescent center (QC) stem cells of the root apical meristem. Emphasis is put on how varying levels of nitric oxide, influenced by the expression of phytoglobins, affect QC response to hypoxic stress.

Extraskeletal Myxoid Chondrosarcoma Identified in a Traumatic Fracture of the Toe: A Case Report.

Introduction: Extraskeletal myxoid chondrosarcoma (EMC) is a rare soft-tissue sarcoma that typically presents in the proximal lower extremity and limb-girdle. It can be easily misdiagnosed, especially when located in atypical locations like the foot. Case Report: We present the case of an 80-year-old Caucasian female with a left 3rd toe pain and swelling that was initially misdiagnosed as a traumatic fracture on radiographs but later determined to be an indolent EMC based on histology. She was successfully treated with amputation of the toe. Conclusion: EMC should be considered in the differential of osseous and soft-tissue abnormalities on radiographic imaging of the extremities. As reported in the literature, it can present in atypical locations with minimal symptoms and successful treatments include resection. Future cases presenting similarly should be evaluated for EMC and, if present, reported along with their applied treatment protocols to allow for further assessment of current therapeutic guidelines.

Arabidopsis root apical meristem survival during waterlogging is determined by phytoglobin through nitric oxide and auxin.

MAIN CONCLUSION: Over-expression of phytoglobin mitigates the degradation of the root apical meristem (RAM) caused by waterlogging through changes in nitric oxide and auxin distribution at the root tip. Plant performance to waterlogging is ameliorated by the over-expression of the Arabidopsis Phytoglobin 1 (Pgb1) which also contributes to the maintenance of a functional RAM. Hypoxia induces accumulation of ROS and damage in roots of wild type plants; these events were preceded by the exhaustion of the RAM resulting from the loss of functionality of the WOX5-expressing quiescent cells (QCs). These phenotypic deviations were exacerbated by suppression of Pgb1 and attenuated when the same gene was up-regulated. Genetic and pharmacological studies demonstrated that degradation of the RAM in hypoxic roots is attributed to a reduction in the auxin maximum at the root tip, necessary for the specification of the QC. This reduction was primarily caused by alterations in PIN-mediated auxin flow but not auxin synthesis. The expression and localization patterns of several PINs, including PIN1, 2, 3 and 4, facilitating the basipetal translocation of auxin and its distribution at the root tip, were altered in hypoxic WT and Pgb1-suppressing roots but mostly unchanged in those over-expressing Pgb1. Disruption of PIN1 and PIN2 signal in hypoxic roots suppressing Pgb1 initiated in the transition zone at 12 h and was specifically associated to the absence of Pgb1 protein in the same region. Exogenous auxin restored a functional RAM, while inhibition of the directional auxin flow exacerbated the degradation of the RAM. The regulation of root behavior by Pgb1 was mediated by nitric oxide (NO) in a model consistent with the recognized function of Pgbs as NO scavengers. Collectively, this study contributes to our understanding of the role of Pgbs in preserving root meristem function and QC niche during conditions of stress, and suggests that the root transition zone is most vulnerable to hypoxia.

Consolidation Carnival: A Case-Based Approach to Reviewing Musculoskeletal Anatomy in an Undergraduate Medical Curriculum.

Introduction: Recent changes in undergraduate medical curricula have resulted in time constraints that are particularly challenging, especially when students must learn large blocks of musculoskeletal anatomy content. Consequently, students have resorted to rote memorization to cope, which counteracts our established collaborative self-directed learning model. Methods: For a 6-week musculoskeletal anatomy course, two structured case-based review sessions are described, each following the completion of two five-hour lab sessions, two on the upper extremities and two on the lower extremities. These largely self-directed review sessions consisted of 6 students rotating through 7 to 8 stations every 10 minutes where clinical cases with follow-up questions were projected on large screens. The students were expected to work collaboratively to solve the cases utilizing the prosected specimens provided and discuss the accompanying answers at the end of each case. Results: Ninety-four per cent of the students who participated in this study agreed that the case-based review sessions provided a helpful overview of musculoskeletal anatomy content. Student performance on the open-ended, case-based musculoskeletal examination questions showed no significant difference in performance on shoulder, hand, hip, thigh, and leg questions. There was, however, a statistically significant decrease in the students' scores on a forearm question in 2021 compared to 2019. Conclusion: This paper describes our integrated, collaborative musculoskeletal course, including case-based review sessions, which was positively received by students as having value in reviewing the musculoskeletal content though it was not found to improve examination performance.

Quitting behavior during the tobacco sales ban in South Africa: Results from a broadly nationally representative survey.

INTRODUCTION: In response to COVID-19, the South African government banned the sale of tobacco products for 20 weeks. Before the ban, the illicit cigarette market was well-entrenched and smoking cessation services were not widely available. Several surveys conducted to ascertain cigarette smokers' responses to the ban reported substantial differences in the proportion of smokers who quit. This study provides a broadly nationally representative ex-post investigation into cigarette smokers' quitting behavior related to the sales ban. METHODS: We used data from wave three of NIDS-CRAM (the National Income Dynamics Study-Coronavirus Rapid Mobile Survey) conducted in November-December 2020. We first investigated the proportion of people who quit and who continued smoking during and after the sales ban. We subsequently linked the NIDS-CRAM survey to the fifth wave of NIDS (2017) to identify a subset of established smokers, and considered whether their quitting behavior differed from that of all smokers who smoked at the start of the sales ban. RESULTS: The cross-sectional analysis showed that 7.8% of cigarette smokers quit during the sales ban, but that 55% of these quitters relapsed after it was lifted. Of the pre-ban smokers, 3.5% indicated that they did not smoke both during and after the sales ban, and 3.7% quit after the ban was lifted. The longitudinal analysis showed that 7% of people who were smoking in 2017, quit smoking cigarettes during the tobacco sales ban, but that >70% of quitters relapsed after it was lifted. Only 2% of pre-ban established smokers indicated that they did not smoke during or after the ban. CONCLUSIONS: The sales ban did not have the intended objective of encouraging large-scale smoking cessation. This reflects policy failures to provide smokers with appropriate cessation support and to effectively control the illicit market both prior to and during the sales ban.

Seed-specific expression of the class 2 Phytoglobin (Pgb2) increases seed oil in Brassica napus.

To examine the function of phytoglobin 2 (Pgb2) on seed oil level in the oil-producing crop Brassica napus L., we generated transgenic plants in which BnPgb2 was over-expressed in the seeds using the cruciferin1 promoter. Over-expression of BnPgb2 elevated the amount of oil, which showed a positive relationship with the level of BnPgb2, without altering the oil nutritional value, as evidenced by the lack of major changes in composition of fatty acids (FA), and key agronomic traits. Two key transcription factors, LEAFY COTYLEDON1 (LEC1) and WRINKLED1 (WRI1), known to promote the synthesis of fatty acids (FA) and potentiate oil accumulation, were induced in BnPgb2 over-expressing seeds. The concomitant induction of several enzymes of sucrose metabolism, SUCROSE SYNTHASE1 (SUS) 1 and 3, FRUCTOSE BISPHOSPHATE ALDOLASE (FPA), and PHOSPHOGLYCERATE KINASE (PGK), and starch synthesis, ADP-GLUCOSE PHOSPHORYLASE (AGPase) suggests that BnPgb2 favors sugar mobilization for FA production. The two plastid FA biosynthetic enzymes SUBUNIT A OF ACETYL-CoA CARBOXYLASE (ACCA2), and MALONYL-CoA:ACP TRANSACYLASE (MCAT) were also up-regulated by the over-expression of BnPgb2. The requirement of BnPgb2 for oil deposition was further evidenced in natural germplasm by the higher levels of BnPgb2 in seeds of high-oil genotypes relative to their low-oil counterparts.