A rare non-canonical splice site in Trema orientalis SYMRK does not affect its dual symbiotic functioning in endomycorrhiza and rhizobium nodulation.

BACKGROUND: Nitrogen-fixing nodules occur in ten related taxonomic lineages interspersed with lineages of non-nodulating plant species. Nodules result from an endosymbiosis between plants and diazotrophic bacteria; rhizobia in the case of legumes and Parasponia and Frankia in the case of actinorhizal species. Nodulating plants share a conserved set of symbiosis genes, whereas related non-nodulating sister species show pseudogenization of several key nodulation-specific genes. Signalling and cellular mechanisms critical for nodulation have been co-opted from the more ancient plant-fungal arbuscular endomycorrhizal symbiosis. Studies in legumes and actinorhizal plants uncovered a key component in symbiotic signalling, the LRR-type SYMBIOSIS RECEPTOR KINASE (SYMRK). SYMRK is essential for nodulation and arbuscular endomycorrhizal symbiosis. To our surprise, however, despite its arbuscular endomycorrhizal symbiosis capacities, we observed a seemingly critical mutation in a donor splice site in the SYMRK gene of Trema orientalis, the non-nodulating sister species of Parasponia. This led us to investigate the symbiotic functioning of SYMRK in the Trema-Parasponia lineage and to address the question of to what extent a single nucleotide polymorphism in a donor splice site affects the symbiotic functioning of SYMRK. RESULTS: We show that SYMRK is essential for nodulation and endomycorrhization in Parasponia andersonii. Subsequently, it is revealed that the 5'-intron donor splice site of SYMRK intron 12 is variable and, in most dicotyledon species, doesn't contain the canonical dinucleotide 'GT' signature but the much less common motif 'GC'. Strikingly, in T. orientalis, this motif is converted into a rare non-canonical 5'-intron donor splice site 'GA'. This SYMRK allele, however, is fully functional and spreads in the T. orientalis population of Malaysian Borneo. A further investigation into the occurrence of the non-canonical GA-AG splice sites confirmed that these are extremely rare. CONCLUSION: SYMRK functioning is highly conserved in legumes, actinorhizal plants, and Parasponia. The gene possesses a non-common 5'-intron GC donor splice site in intron 12, which is converted into a GA in T. orientalis accessions of Malaysian Borneo. The discovery of this functional GA-AG splice site in SYMRK highlights a gap in our understanding of splice donor sites.

Sexual reproduction contributes to the evolution of resistance-breaking isolates of the spinach pathogen Peronospora effusa.

Peronospora effusa causes downy mildew, the economically most important disease of cultivated spinach worldwide. To date, 19 P. effusa races have been denominated based on their capacity to break spinach resistances, but their genetic diversity and the evolutionary processes that contribute to race emergence are unknown. Here, we performed the first systematic analysis of P. effusa races showing that those emerge by both asexual and sexual reproduction. Specifically, we studied the diversity of 26 P. effusa isolates from 16 denominated races based on mitochondrial and nuclear comparative genomics. Mitochondrial genomes based on long-read sequencing coupled with diversity assessment based on short-read sequencing uncovered two mitochondrial haplogroups, each with distinct genome organization. Nuclear genome-wide comparisons of the 26 isolates revealed that 10 isolates from six races could clearly be divided into three asexually evolving groups, in concordance with their mitochondrial phylogeny. The remaining isolates showed signals of reticulated evolution and discordance between nuclear and mitochondrial phylogenies, suggesting that these evolved through sexual reproduction. Increased understanding of this pathogen's reproductive modes will provide the framework for future studies into the molecular mechanisms underlying race emergence and into the P. effusa-spinach interaction, thus assisting in sustainable production of spinach through knowledge-driven resistance breeding.

Pseudogenization of the rhizobium-responsive EXOPOLYSACCHARIDE RECEPTOR in Parasponia is a rare event in nodulating plants.

BACKGROUND: Nodule symbiosis with diazotrophic Frankia or rhizobium occurs in plant species belonging to ten taxonomic lineages within the related orders Fabales, Fagales, Cucurbitales, and Rosales. Phylogenomic studies indicate that this nitrogen-fixing nodulation trait has a single evolutionary origin. In legume model plants, the molecular interaction between plant and rhizobium microsymbiont is mapped to a significant degree. A specific LysM-type receptor kinase, LjEPR3 in Lotus japonicus and MtLYK10 in Medicago truncatula, was found to act in a secondary identity-based mechanism, controlling intracellular rhizobium infection. Furthermore, LjEPR3 showed to bind surface exopolysaccharides of Mesorhizobium loti, the diazotrophic microsymbiont of L. japonicus. EPR3 orthologous genes are not unique to legumes. Surprisingly, however, its ortholog EXOPOLYSACCHARIDE RECEPTOR (EPR) is pseudogenized in Parasponia, the only lineage of non-legume plants that nodulate also with rhizobium. RESULTS: Analysis of genome sequences showed that EPR3 orthologous genes are highly conserved in nodulating plants. We identified a conserved retrotransposon insertion in the EPR promoter region in three Parasponia species, which associates with defected transcriptional regulation of this gene. Subsequently, we studied the EPR gene of two Trema species as they represent the sister genus of Parasponia for which it is assumed it lost the nitrogen-fixing nodulation trait. Both Trema species possess apparently functional EPR genes that have a nodulation-specific expression profile when introduced into a Parasponia background. This indicates the EPR gene functioned in nodulation in the Parasponia-Trema ancestor. CONCLUSION: We conclude that nodule-specific expression of EPR3 orthologous genes is shared between the legume and Parasponia-Trema lineage, suggesting an ancestral function in the nitrogen-fixing nodulation trait. Pseudogenization of EPR in Parasponia is an exceptional case in nodulating plants. We speculate that this may have been instrumental to the microsymbiont switch -from Frankia to rhizobium- that has occurred in the Parasponia lineage and the evolution of a novel crack entry infection mechanism.

NIN is essential for development of symbiosomes, suppression of defence and premature senescence in Medicago truncatula nodules.

NIN (NODULE INCEPTION) is a transcription factor that plays a key role during root nodule initiation. However, its role in later nodule developmental stages is unclear. Both NIN mRNA and protein accumulated at the highest level in the proximal part of the infection zone in Medicago truncatula nodules. Two nin weak allele mutants, nin-13/16, form a rather normal nodule infection zone, whereas a fixation zone is not formed. Instead, a zone with defence responses and premature senescence occurred and symbiosome development gets arrested. Mutations in nin-13/16 resulted in a truncated NIN lacking the conserved PB1 domain. However, this did not cause the nodule phenotype as nin mutants expressing NINΔPB1 formed wild-type-like nodule. The phenotype is likely to be caused by reduced NIN mRNA levels in the cytoplasm. Transcriptome analyses of nin-16 nodules showed that expression levels of defence/senescence-related genes are markedly increased, whereas the levels of defence suppressing genes are reduced. Although defence/senescence seems well suppressed in the infection zone, the transcriptome is already markedly changed in the proximal part of infection zone. In addition to its function in infection and nodule organogenesis, NIN also plays a major role at the transition from infection to fixation zone in establishing a functional symbiosis.

The Genome of Peronospora belbahrii Reveals High Heterozygosity, a Low Number of Canonical Effectors, and TC-Rich Promoters.

Along with Plasmopara destructor, Peronosopora belbahrii has arguably been the economically most important newly emerging downy mildew pathogen of the past two decades. Originating from Africa, it has started devastating basil production throughout the world, most likely due to the distribution of infested seed material. Here, we present the genome of this pathogen and results from comparisons of its genomic features to other oomycetes. The assembly of the nuclear genome was around 35.4 Mbp in length, with an N50 scaffold length of around 248 kbp and an L50 scaffold count of 46. The circular mitochondrial genome consisted of around 40.1 kbp. From the repeat-masked genome, 9,049 protein-coding genes were predicted, out of which 335 were predicted to have extracellular functions, representing the smallest secretome so far found in peronosporalean oomycetes. About 16% of the genome consists of repetitive sequences, and, based on simple sequence repeat regions, we provide a set of microsatellites that could be used for population genetic studies of P. belbahrii. P. belbahrii has undergone a high degree of convergent evolution with other obligate parasitic pathogen groups, reflecting its obligate biotrophic lifestyle. Features of its secretome, signaling networks, and promoters are presented, and some patterns are hypothesized to reflect the high degree of host specificity in Peronospora species. In addition, we suggest the presence of additional virulence factors apart from classical effector classes that are promising candidates for future functional studies.

Quarterly Reporting of Computed Tomography Ordering History Reduces the Use of Imaging in an Emergency Department.

BACKGROUND: Computed tomography (CT) is a useful and necessary part of many emergency department (ED) assessments. However, the costs of imaging and the health risks associated with radiation exposure have sparked national efforts to reduce CT ordering in EDs. STUDY OBJECTIVE: We analyzed CT ordering habits prior to and following implementation of a feedback tool at a community hospital. METHODS: In this intervention study, we identified the CT-ordering habits of physicians and mid-level care providers (physician assistants and nurse practitioners) at baseline and after implementation of a system that sent quarterly feedback reports comparing their ordering habits with those of their peers. Variability in ordering and subgroup analyses by body region were included in these reports. RESULTS: We examined the records of 104,454 patients seen between October 1, 2013 and December 31, 2014. There were 5552 or 21.0% of patients seen during the baseline period that underwent CT imaging. We observed an absolute reduction in imaging of 2.3% (95% confidence interval 1.7-2.8%) after implementation, avoiding approximately $400,000 in costs, 22 days of scanning time, and radiation exposure equivalent to 33,000 chest films annually. These changes occurred across physicians and mid-level providers, regardless of the number years of practice or board certification. CONCLUSIONS: Implementation of a feedback mechanism reduced CT use by emergency medicine practitioners, with concomitant reductions in cost and radiation exposure. The change was similar across levels of medical care. Future studies will examine the effect of the feedback reporting system at other institutions in our hospital network.

Genome analyses of the sunflower pathogen Plasmopara halstedii provide insights into effector evolution in downy mildews and Phytophthora.

BACKGROUND: Downy mildews are the most speciose group of oomycetes and affect crops of great economic importance. So far, there is only a single deeply-sequenced downy mildew genome available, from Hyaloperonospora arabidopsidis. Further genomic resources for downy mildews are required to study their evolution, including pathogenicity effector proteins, such as RxLR effectors. Plasmopara halstedii is a devastating pathogen of sunflower and a potential pathosystem model to study downy mildews, as several Avr-genes and R-genes have been predicted and unlike Arabidopsis downy mildew, large quantities of almost contamination-free material can be obtained easily. RESULTS: Here a high-quality draft genome of Plasmopara halstedii is reported and analysed with respect to various aspects, including genome organisation, secondary metabolism, effector proteins and comparative genomics with other sequenced oomycetes. Interestingly, the present analyses revealed further variation of the RxLR motif, suggesting an important role of the conservation of the dEER-motif. Orthology analyses revealed the conservation of 28 RxLR-like core effectors among Phytophthora species. Only six putative RxLR-like effectors were shared by the two sequenced downy mildews, highlighting the fast and largely independent evolution of two of the three major downy mildew lineages. This is seemingly supported by phylogenomic results, in which downy mildews did not appear to be monophyletic. CONCLUSIONS: The genome resource will be useful for developing markers for monitoring the pathogen population and might provide the basis for new approaches to fight Phytophthora and downy mildew pathogens by targeting core pathogenicity effectors.

Daniel Sennert, The Philosophical Hen, and The Epistolary Quest for a (Nearly-) Universal Medicine.

This article explores the Wittenberg Professor Daniel Sennert's (1572-1637) pursuit of nearly universal medicines made from noble metals, which he described in his published works and in private correspondence with his brother-in-law, Michael Döring. Of the medicaments that Sennert sought, one called the Philosophical Hen was especially interesting, and involved feeding a hen silver or gold during propitious astrological conjunctions. Sennert's support of this experiment was rooted in his obsession with experience and can be partially explained by looking to an extensive tradition of natural philosophy and natural history. Sennert explained such nearly universal medicines according to the rational principles of academic medicine, arguing that they strengthened the body's innate heat or acted as universal purgatives. From Sennert's candid epistles, we receive a more historicised portrait of the collaborative experimental process by which chymical medicines were conceptualised and tested, and how the consequences of experimental failure and perceived credulity could be increased scepticism.

QTL-seq identifies an early flowering QTL located near Flowering Locus T in cucumber.

KEY MESSAGE: Next-generation sequencing enabled a fast discovery of a major QTL controlling early flowering in cucumber, corresponding to the FT gene conditioning flowering time in Arabidopsis. Next-generation sequencing technologies are making it faster and more efficient to establish the association of agronomic traits with molecular markers or candidate genes, which is the requirement for marker-assisted selection in molecular breeding. Early flowering is an important agronomic trait in cucumber (Cucumis sativus L.), but the underlying genetic mechanism is unknown. In this study, we identified a candidate gene for early flowering QTL, Ef1.1 through QTL-seq. Segregation analysis in F2 and BC1 populations derived from a cross between two inbred lines "Muromskij" (early flowering) and "9930" (late flowering) suggested quantitative nature of flowering time in cucumber. Genome-wide comparison of SNP profiles between the early and late-flowering bulks constructed from F2 plants identified a major QTL, designated Ef1.1 on cucumber chromosome 1 for early flowering in Muromskij, which was confirmed by microsatellite marker-based classical QTL mapping in the F2 population. Joint QTL-seq and traditional QTL analysis delimited Ef1.1 to an 890 kb genomic region. A cucumber gene, Csa1G651710, was identified in this region, which is a homolog of the FLOWERING LOCUS T (FT), the main flowering switch gene in Arabidopsis. Quantitative RT-PCR study of the expression level of Csa1G651710 revealed significantly higher expression in early flowering genotypes. Data presented here provide support for Csa1G651710 as a possible candidate gene for early flowering in the cucumber line Muromskij.

Corporeal elements and principles in the learned German chymical tradition.

This paper explores diverse conceptions of the physicality and tangibility of elements and principles in early modern chymistry. By tracing the development of natural philosophical and corpuscular ideas about material elements and principles among several physicans and chymists, including Thomas Erastus, Andreas Libavius, Daniel Sennert, and Anton Günther Billich, this article locates a learned tradition that developed predominantly in Germany, and which directly challenged a common understanding of matter held by major Paracelsians as well as authors from the French textbook tradition. Likewise, conceptions of incorporeal elements or principles are shown to have developed from the ideas of Paracelsus and Petrus Severinus, whereas authors in the learned tradition emphasised a particular interpretation of Aristotle. The article concludes by suggesting that chymical interpretations of material composition had an important influence throughout the seventeenth and eighteenth centuries, and that this provides further evidence that the so-called "compositional revolution" in chemistry was well underway prior to the eighteenth century.

Are patients with knee osteoarthritis aware that platelet-rich plasma is a treatment option?

Osteoarthritis (OA) is a prevalent joint disease, particularly affecting the knees. This condition is often managed through various treatments, including intra-articular injections such as corticosteroids (CS), hyaluronic acid (HA), and platelet-rich plasma (PRP). PRP has shown promising outcomes in recent studies although it does lack strong endorsement in some clinical guidelines due to inconsistent results and lack of standardized results. This study was conducted to assess patient awareness and the frequency of PRP offered for the treatment of knee OA, compared to CS and HA. In a cross-sectional study, 46 knee OA patients were surveyed regarding their knowledge and experiences of CS, HA, and PRP injections. The questionnaires were administered between September 2022 and February 2023. Additionally, the study evaluated the severity of patients knee OA, using the Western Ontario and McMaster Universities Arthritis Index, and gathered demographic information from the participants. CS injections were offered to 93.5%, and 100% of participants had previously heard of this type of injection. HA injections were offered to 37%, and 65.9% of participants had heard of them. PRP was offered to 2%, and 6.5% had ever heard of it. This study underscores the limited awareness and utilization of PRP among knee OA patients. Patients and physicians need to be more informed of all of the treatment options available for knee OA, especially orthobiologics such as PRP. Future research in larger, diverse populations is needed.

Concussion Reduction in Division I and II Athletes: Effects of Simple Cervical Spine Exercise Regimen.

INTRODUCTION:  Primary preventative medicine lacks a consensus on effective concussion prevention strategies for collegiate athletes. Cervical strength has been identified as a potential factor in concussion risk reduction. This study evaluates the impact of a commercially available, portable cervical muscle stretching and strengthening device, NeckX®, on cervical strength, range of motion (ROM), and concussion incidence in collegiate athletes participating in high-concussion-risk sports. METHODS:  A single-arm prospective cohort study was conducted with 162 collegiate athletes from various sports. Participants underwent a 12-week neck exercise protocol using the NeckX® device. Clinical data, including neck strength and ROM, were collected at weeks 0, 6, and 12. Concussion incidence was self-reported by participants and cross-referenced with records from the athletic department. Data were analyzed for significant neck strength and ROM changes throughout the 12-week study. A two-way analysis of variance multiple comparisons with the Tukey-Kramer significant difference test was utilized, using the Holm-Sidak method, with an alpha of 0.05. RESULTS:  All athletic teams experienced a significant increase in cervical strength during the 12-week intervention (α = 0.05, p < 0.05). Increases in cervical flexion and extension force were most consistent between teams. Cervical ROM increased significantly in male and female soccer players (α = 0.05, p < 0.05). The overall incidence of head and neck injuries, including concussions, was reduced to 6.60% during the study period, the lowest recorded value in the university's athletic department history. CONCLUSION:  The use of the NeckX® device for 12 weeks was effective in enhancing pericervical muscle strength and ROM while reducing concussion incidence in collegiate athletes participating in high-concussion-risk sports. Interestingly, the positive outcomes were consistent for both males and females, indicating the universal advantages of neck training among collegiate athletes. These findings support existing research on the benefits of cervical strengthening exercises for reducing concussions in collegiate athletes and highlight the convenience and affordability of using this device.

The impact of automatic physician review of prescription drug monitoring program data on opioid prescribing in a Maryland statewide hospital system.

BACKGROUND AND AIMS: Prescription drug monitoring programs (PDMPs) were implemented to decrease dangerous opioid prescribing but have had variable results. This report details how automatic PDMP review changed opioid prescribing across a statewide medical system. DESIGN: An observational study. SETTING: Fourteen hospital networks in the United States. CASES: Healthcare encountered from July 1, 2016 to June 30, 2019. INTERVENTION: Starting from July 1, 2018, the patient's PDMP data would be displayed automatically to providers in the unified electronic medical record (EMR) whenever the provider began to write for an opioid prescription. MEASUREMENTS: Outcomes were prescriptions per encounter (PPE) and the morphine milligram equivalents (MME) per prescription. Outcomes were stratified by practice location, medication prescribed, and diagnosis. All data, including whether the prompt was triggered for a given encounter and whether a prescription was given, were extracted from the EMR. An interrupted timeseries analysis was used to determine how PPE and MME changed in response to the implementation of automatic PDMP review. FINDINGS: Of the 624,488 encounters examined, 18.37 percent (n = 114,710) were in emergency departments, 56.79 percent were admissions (n = 354,634), and 24.84 percent (n = 155,144) were outpatient visits. Opioid prescriptions were started and then canceled 24 percent of the time after the PDMP was shown. There was a decline in MME (ßOverall + Policy Trends = -3.17, p = <0.0001), which was driven by inpatient (ßOverall + Policy Trends = -2.10, p < 0.0001) and outpatient providers (ßOverall + Policy Trends = -3.24, p < 0.01). A decline in MME was seen in all medication categories (-1.72 < ßOverall + Policy Trends < -5.87, p < 0.01). There were no changes in these trends after excluding encounters for severe and acute pain. CONCLUSIONS: Automated PDMP review is associated with fewer prescriptions and smaller doses without decreasing appropriate use.

Genome reconstruction of the non-culturable spinach downy mildew Peronospora effusa by metagenome filtering.

Peronospora effusa (previously known as P. farinosa f. sp. spinaciae, and here referred to as Pfs) is an obligate biotrophic oomycete that causes downy mildew on spinach (Spinacia oleracea). To combat this destructive many disease resistant cultivars have been bred and used. However, new Pfs races rapidly break the employed resistance genes. To get insight into the gene repertoire of Pfs and identify infection-related genes, the genome of the first reference race, Pfs1, was sequenced, assembled, and annotated. Due to the obligate biotrophic nature of this pathogen, material for DNA isolation can only be collected from infected spinach leaves that, however, also contain many other microorganisms. The obtained sequences can, therefore, be considered a metagenome. To filter and obtain Pfs sequences we utilized the CAT tool to taxonomically annotate ORFs residing on long sequences of a genome pre-assembly. This study is the first to show that CAT filtering performs well on eukaryotic contigs. Based on the taxonomy, determined on multiple ORFs, contaminating long sequences and corresponding reads were removed from the metagenome. Filtered reads were re-assembled to provide a clean and improved Pfs genome sequence of 32.4 Mbp consisting of 8,635 scaffolds. Transcript sequencing of a range of infection time points aided the prediction of a total of 13,277 gene models, including 99 RxLR(-like) effector, and 14 putative Crinkler genes. Comparative analysis identified common features in the predicted secretomes of different obligate biotrophic oomycetes, regardless of their phylogenetic distance. Their secretomes are generally smaller, compared to hemi-biotrophic and necrotrophic oomycete species. We observe a reduction in proteins involved in cell wall degradation, in Nep1-like proteins (NLPs), proteins with PAN/apple domains, and host translocated effectors. The genome of Pfs1 will be instrumental in studying downy mildew virulence and for understanding the molecular adaptations by which new isolates break spinach resistance.

Integrating a safety smart list into the electronic health record decreases intensive care unit length of stay and cost.

PURPOSE: To measure how an integrated smartlist developed for critically ill patients would change intensive care units (ICUs) length of stay (LOS), mortality, and charges. MATERIALS AND METHODS: Propensity-score analysis of adult patients admitted to one of 14 surgical and medical ICUs between June 2017 and May 2018. The smart list aimed to certain preventative measures for all critical patients (e.g., removing unneeded catheters, starting thromboembolic prophylaxis, etc.) and was integrated into the electronic health record workflows at the hospitals under study. RESULTS: During the study period, 11,979 patients were treated in the 14 participating ICUs by 518 unique providers. Patients who had the smart list used during ≥60% of their ICU stay (N = 432 patients, 3.6%) were significantly more likely to have a shorter ICU LOS (HR = 1.20, 95% CI:1.0 to 1.4, p = 0.015) with an average decrease of -$1218 (95% CI: -$1830 to -$607, P < 0.001) in the amount charged per day. The intervention cohort had fewer average ventilator days (3.05 vent days, SD = 2.55) compared to propensity score matched controls (3.99, SD = 4.68, p = 0.015), but no changes in mortality (16.7% vs 16.0%, p = 0.78). CONCLUSIONS: An integrated smart list shortened LOS and lowered charges in a diverse cohort of critically ill patients.

Antimicrobial prescription errors in hospitalized children: role of antimicrobial stewardship program in detection and intervention.

BACKGROUND: Antimicrobial stewardship programs (ASP) are an effective strategy to ensure that antibiotics are used in accordance with scientific evidence to improve patient outcome, minimize antimicrobial (AM) resistance, and reduce hospital costs. The article describes the impact of the implementation of an ASP on AM prescription errors. METHODS: Prospective, single-center study performed at a tertiary pediatric teaching hospital that actively monitored 13 targeted AMs (amikacin, amphotericin B, cefepime, ceftriaxone, ciprofloxacin, fluconazole, levofloxacin, linezolid, meropenem, piperacillin-tazobactam, tobramycin, vancomycin, and voriconazole) and microbiology data. The ASP was implemented using CareNet and PharmNet. An infectious disease physician and pharmacist determined the need for intervention. RESULTS: The authors screened 5564 dispensed prescriptions of the 13 targeted AMs. The rate of AM errors associated with these was 0.09/1000 doses administered and 5 errors/1000 patient days. CONCLUSIONS: Active surveillance and optimization of computerized physician order entry system allows early detection and intervention of AMs prescriptions errors in hospitalized children.

Recognition of lettuce downy mildew effector BLR38 in Lactuca serriola LS102 requires two unlinked loci.

Plant-pathogenic oomycetes secrete effector proteins to suppress host immune responses. Resistance proteins may recognize effectors and activate immunity, which is often associated with a hypersensitive response (HR). Transient expression of effectors in plant germplasm and screening for HR has proven to be a powerful tool in the identification of new resistance genes. In this study, 14 effectors from the lettuce downy mildew Bremia lactucae race Bl:24 were screened for HR induction in over 150 lettuce accessions. Three effectors-BLN06, BLR38 and BLR40-were recognized in specific lettuce lines. The recognition of effector BLR38 in Lactuca serriola LS102 did not co-segregate with resistance against race Bl:24, but was linked to resistance against multiple other B. lactucae races. Two unlinked loci are both required for effector recognition and are located near known major resistance clusters. Gene dosage affects the intensity of the BLR38-triggered HR, but is of minor importance for disease resistance.

A liquid chromatographic-mass spectrometric method to evaluate the distribution kinetics of 1,2-diethylbenzene and its metabolite 1,2-diacetylbenzene in the F344 male rat.

Diethylbenzene (DEB) is a moderately volatile, colorless liquid found in gasoline, kerosene, and fuel oils. Exposure to DEB has been shown to produce peripheral neuropathy in rats, and the ortho isomer of DEB (1,2-DEB) is generally believed to be the isomer responsible. 1,2-DEB is assumed to be metabolized primarily by direct oxidation of the ethyl side chain to form two enantiomers of 1-(2-ethylphenol) ethanol and their glucuroconjugates, which are the main 1,2-DEB metabolites, and 1,2-diacetylbenzene (1,2-DAB), a minor metabolite. The metabolite 1,2-DAB appears to be a chromogenic neurotoxin. A liquid chromatographic-mass spectrometric (LC-MS) method using atmospheric pressure photoionization (APPI) for quantifying 1,2-DEB and 1,2-DAB in blood, urine, and brain tissues from animals treated with an intraperitoneal injection of 1,2-DEB was developed. Calibration curves were prepared using matrix-specific standards with concentrations ranging from 0.068 to 402 microM. Results indicate that the concentration of 1,2-DEB in blood peaked at 2 h post intraperitoneal injection and rapidly declined thereafter. In contrast, 1,2-DAB levels in blood were fairly constant up to 24 h postinjection. Urine concentrations of 1,2-DEB were highest at the first collection interval (0-12 h postinjection), and dropped rapidly thereafter; concentrations at 24 h were similar to concentrations observed at 48 h postexposure. Urine concentrations of 1,2-DAB, however, showed the reverse, with peak concentrations observed at 24 h postinjection and only a slight decrease in concentration by 48 h.