Biology subjects

Kim, Y. S.

Publications and source records attributed to Kim, Y. S..

54 records · Page 3Linked to original sources

bioRxiv2021

Overexpression of NDR1 Leads to Pathogen Resistance at Elevated Temperatures

Abiotic and biotic environments influence a myriad of plant-related processes, including growth, development, and the establishment and maintenance of interaction(s) with microbes. As a driver of this signaling between plants and microbes, the role of plant hormones in both surveillance and signaling has emerged as a point of intersection between plant-abiotic and -biotic responses. In the current study, we elucidate a role for NON-RACE-SPECIFIC DISEASE RESISTANCE1 (NDR1) by exploiting effector-triggered immunity (ETI) to define the regulation of plant host immunity in response to both pathogen infection and elevated temperature. We generated time-series RNA sequencing data of WT Col-0, a NDR1 overexpression line, as well as ndr1 and ics1-2 mutant plants under elevated temperature. Not surprisingly, the NDR1-overexpression line showed genotype-specific gene expression changes related to defense response and immune system function. Interestingly, overexpression of NDR1 revealed a role for NDR1 in immune system function; specifically, we describe a mechanism that intersects with Pseudomonas syringae, type-III effector translocation, R-protein signaling complex stabilization, and sustained levels of SA at elevated temperature during ETI. The results described herein support a role for NDR1 in maintaining cell signaling during simultaneous exposure to elevated temperature and avirulent pathogen stressors. One-sentence summaryNDR1 is required for Pst-AvrRpt2 triggered ETI at elevated temperature.

plant biology↗

bioRxiv2021

Intravital imaging of cerebral microinfarct reveals an astrocyte reaction led to glial scar

Cerebral microinfarct increases the risk of dementia. But how microscopic cerebrovascular disruption affects the brain tissue in cellular-level are mostly unknown. Herein, with a longitudinal intravital imaging, we serially visualized in vivo dynamic cellular-level changes in astrocyte, pericyte and neuron as well as microvascular integrity after the induction of cerebral microinfarction for 1 month in mice. At day 2-3, it revealed a localized edema with acute astrocyte loss, neuronal death, impaired pericyte-vessel coverage and extravascular leakage indicating blood-brain barrier (BBB) dysfunction. At day 5, edema disappeared with recovery of pericyte-vessel coverage and BBB integrity. But brain tissue continued to shrink with persisted loss of astrocyte and neuron in microinfarct until 30 days, resulting in a collagen-rich fibrous scar surrounding the microinfarct. Notably, reactive astrocytes appeared at the peri-infarct area early at day 2 and thereafter accumulated in the peri-infarct. Oral administration of a reversible monoamine oxidase B inhibitor significantly decreased the astrocyte reactivity and fibrous scar formation. Our result suggests that astrocyte reactivity may be a key target to alleviate the impact of microinfarction.

neuroscience↗

bioRxiv2021

A merger between compatible but divergent genomes supports allopolyploidization in the Brassicaceae family

Hybridization and polyploidization are pivotal to plant evolution. Genetic crosses between distantly related species rarely occur in nature mainly due to reproductive barriers but how such hurdles can be overcome is largely unknown. xBrassicoraphanus is a fertile intergeneric allopolyploid synthesized between Brassica rapa and Raphanus sativus in the Brassicaceae family. Genomes of B. rapa and R. sativus are diverged enough to suppress synapsis formation between non-homologous progenitor chromosomes during meiosis, and we found that both genomes reside in the single nucleus of xBrassicoraphanus without genome loss or rearrangement. Expressions of syntenic orthologs identified in B. rapa and R. sativus were adjusted to a hybrid nuclear environment of xBrassicoraphanus, which necessitates reconfiguration of transcription network by rewiring cis-trans interactions. B. rapa coding sequences have a higher level of gene-body methylation than R. sativus, and such methylation asymmetry is maintained in xBrassicoraphanus. B. rapa-originated transposable elements were transcriptionally silenced in xBrassicoraphanus, rendered by gain of CHG methylation in trans via small RNAs derived from the same sequences of R. sativus subgenome. Our work proposes that not only transcription compatibility but also a certain extent of genome divergence supports hybrid genome stabilization, which may explain great diversification and expansion of angiosperms during evolution.

plant biology↗

bioRxiv2021

Structural basis for channel conduction in the pump-like channelrhodopsin ChRmine

ChRmine1, a recently-discovered bacteriorhodopsin-like cation-conducting channelrhodopsin1, 2, exhibits puzzling properties (unusually-large photocurrents, exceptional red-shift in action spectrum, and extreme light-sensitivity) that have opened up new opportunities in optogenetics1, 3-5. ChRmine and its homologs function as light-gated ion channels, but by primary sequence more closely resemble ion pump rhodopsins; the molecular mechanisms for passive channel conduction in this family of proteins, as well as the unusual properties of ChRmine itself, have remained mysterious. Here we present the cryo-electron microscopy structure of ChRmine at 2.0 [A] resolution. The structure reveals striking architectural features never seen before in channelrhodopsins including trimeric assembly, a short transmembrane-helix 3 unwound in the middle of the membrane, a prominently-twisting extracellular-loop 1, remarkably-large intracellular cavities and extracellular vestibule, and an unprecedented hydrophilic pore that extends through the center of the trimer, separate from the three individual monomer pores. Electrophysiological, spectroscopic, and computational analyses provide insight into conduction and gating of light-gated channels with these distinct design features, and point the way toward structure-guided creation of novel channelrhodopsins for optogenetic applications in biology.

biophysics↗

bioRxiv2021

Meclizine and metabotropic glutamate receptor agonists attenuate severe pain and primary sensory neuron Ca2+ activity in chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) affects about 68% of patients undergoing chemotherapy and causes severe neuropathic pain which is debilitating health problem and greatly reduces quality of life. Cisplatin is a commonly used platinum-based chemotherapeutic drug known to cause CIPN, possibly by causing oxidative stress damage to primary sensory neurons. Metabotropic glutamate receptors (mGluRs) are widely hypothesized to be involved in pain processing. Meclizine is an H1 histamine receptor antagonist which is known to have neuroprotective effects including anti-oxidative effect. Here, we used a mouse model of cisplatin-induced CIPN to test agonists of mGluR8 and group II mGluR as well as meclizine as interventions to reduce cisplatin-induced pain. We performed behavioral pain tests and in vivo entire DRG neurons Ca2+ imaging using genetically-encoded Ca2+ indicator, Pirt-GCaMP3 to monitor different drug interventions on a populational ensemble level. CIPN induced increased spontaneous Ca2+ activity in DRG neurons, increased Ca2+ transient amplitudes, and hyperresponses to mechanical, thermal, and chemical stimuli. We found mGluR8 agonist, DCPG, group II mGluR agonist, LY379268, and Histamine1 receptor antagonist, meclizine all significantly attenuated mechanical and thermal pain caused by CIPN. LY379268 and meclizine, but not DCPG, attenuated DRG neuronal Ca2+ activity elevated by CIPN. Furthermore, meclizine attenuated cisplatin-induced weight loss. These results suggest group II mGluR agonist, mGluR8 agonist, and meclizine are excellent candidates to study for mechanisms and new treatment option for CIPN.

neuroscience↗

bioRxiv2021

Capsaicin pretreatment alleviates postoperative pain and reduces primary sensory neuron Ca2+ activity

After surgeries, especially thoracotomy incision, patients develop unbearable pain. Opioids are used for reducing pain but often cause serious side effects. Previously, we found that capsaicin pretreatment of the incision area alleviated spontaneous and thermal pain in a postoperative pain animal model. In the present study, we aimed to monitor primary sensory neuron Ca2+ activity in in vivo dorsal root ganglia (DRG) in a postoperative pain model using Pirt-GCaMP3 treated with capsaicin or controls. Intraplantar injection of capsaicin (0.05%) alleviated spontaneous, mechanical, and thermal postoperative pain. The Ca2+ response in in vivo DRG and in in situ spinal cord was significantly enhanced in the ipsilateral side compared to contralateral side or naive control. Primary sensory nerve fiber length was significantly decreased in the incision skin area in capsaicin-pretreated animals detected by immunohistochemistry and placental alkaline phosphatase (PLAP) staining. Thus, capsaicin pretreatment alleviates postoperative pain by suppressing Ca2+ response due to degeneration of primary sensory nerve fibers in the skin.

neuroscience↗

bioRxiv2021

Mast cell-specific receptor/corticotropin-releasing factor axis regulates alcohol withdrawal-associated headache

Rehabilitation from alcohol addiction or abuse is challenging due to alcohol withdrawal symptoms. Headache is a severe alcohol withdrawal symptom that frequently contributes to rehabilitation failure. Despite the need for treating alcohol withdrawal-induced headache, there is no appropriate therapeutic option available. Development of improved therapeutics will depend on obtaining a clearer understanding of alcohol withdrawal-induced headache pain mechanisms. Here, we show that the mast cell-specific receptor MrgprB2 controls development of alcohol withdrawal-induced headache. Withdrawing alcohol from alcohol-acclimated mice induces strong headache behaviors, including facial allodynia, facial pain expressions, and reduced walking movement, symptoms often observed in humans suffering from headache. Observed pain behaviors were abolished in MrgprB2-deficient mice. We observed in vivo spontaneous activation and hypersensitization of trigeminal ganglia neurons in alcohol withdrawal mice, but not in MrgprB2-deficient mice. Corticotropin-releasing factor (CRF) was increased in dura mater after alcohol withdrawal. Injection of CRF into dura mater resulted in activation of trigeminal ganglia neurons and vasodilation, which was accompanied by headache behavior. In cells, CRF evoked Ca2+ transients via MrgprB2 or human MrgprX2. The results indicate that alcohol withdrawal causes headache via mast cell degranulation in dura mater. The process is under control of MrgprB2/MrgprX2, which would appear to represent a potential target for treating alcohol withdrawal-related headache.

neuroscience↗

bioRxiv2021

Viperin inhibits cholesterol biosynthesis and interacts with enzymes in the cholesterol biosynthetic pathway

Many enveloped viruses bud from cholesterol-rich lipid rafts on the cell membrane. Depleting cellular cholesterol impedes this process and results in viral particles with reduced viability. Viperin (virus inhibitory protein endoplasmic reticulum-associated, interferon-induced) is an ER membrane-associated enzyme that when expressed in response to viral infections exerts broad-ranging antiviral effects, including inhibiting the budding of some enveloped viruses. Here we have investigated the effect of viperin expression on cholesterol biosynthesis. We found that viperin expression reduces cholesterol levels by 20 - 30 % in HEK293T cells. A proteomic screen of the viperin interactome identified several cholesterol biosynthetic enzymes among the top hits. The two most highly enriched proteins were lanosterol synthase and squalene monooxygenase, enzymes that catalyze key steps establishing the sterol carbon skeleton. Co-immunoprecipitation experiments established that viperin, lanosterol synthase and squalene monooxygenase form a complex at the ER membrane. Co-expression of viperin was found to significantly inhibit the specific activity of lanosterol synthase in HEK293T cell lysates. Co-expression of viperin had no effect on the specific activity of squalene monooxygenase, but reduced its expression levels in the cells by approximately 30 %. Despite these inhibitory effects, co-expression of either LS or SM failed to reverse the viperin-induced depletion of cellular cholesterol levels in HEK293T cells. Our results establish a clear link between the down-regulation of cholesterol biosynthesis and viperin, although at this point the effect cannot be unambiguously attributed interactions between viperin and a specific biosynthetic enzyme.

biochemistry↗

bioRxiv2021

HuR -dependent SOD2 protein synthesis is an early adaptation of ovarian cancer cells in response to anchorage independence

During metastasis, cancer cells must adapt to survive a loss of anchorage and evade anoikis. An important pro-survival adaptation is the ability of metastatic tumor cells to increase their antioxidant capacity and restore cellular redox balance. Although much is known about the transcriptional regulation of antioxidant enzymes in response to stress, how cells rapidly adapt to alter antioxidant enzyme levels is less well understood. Using ovarian cancer cells as a model, we demonstrate that an increase in protein expression of the mitochondrial superoxide dismutase SOD2 is a very early event initiated in response to cellular detachment. SOD2 protein synthesis is rapidly induced within 0.5-2 hours of matrix detachment, and polyribosome profiling demonstrates an increase in the number of ribosomes bound to SOD2 mRNA, indicating an increase in SOD2 translation in response to anchorage-independence. Mechanistically, we find that anchorage-independence specifically induces cytosolic accumulation of the RNA binding protein HuR/ELAVL1 and leads to increased HuR binding to SOD2 mRNA. Using HuR siRNA-mediated knock-down, we show that the presence of HuR is necessary for the increase in SOD2 mRNA association with the heavy polyribosome fraction and SOD2 protein synthesis observed in anchorage-independence. Cellular detachment activates the stress-response protein kinase p38 MAPK, which is necessary for HuR-SOD2 mRNA binding and optimal increases in SOD2 protein expression. These findings illustrate a novel post-transcriptional regulatory mechanisms of SOD2, enabling cells to rapidly increase their mitochondrial antioxidant capacity as an acute response to anchorage-independence.

cancer biology↗

bioRxiv2021

Mutational impact and signature of ionizing radiation

Whole-genome sequencing (WGS) of human tumors and normal cells exposed to various carcinogens has revealed distinct mutational patterns that provide deep insights into the DNA damage and repair processes. Although ionizing radiation (IR) is conventionally known as a strong carcinogen, its genome-wide mutational impacts have not been comprehensively investigated at the single-nucleotide level. Here, we explored the mutational landscape of normal single-cells after exposure to the various levels of IR. On average, 1 Gy of IR exposure generated [~]16 mutational events with a spectrum consisting of predominantly small nucleotide deletions and a few characteristic structural variations. In [~]30% of the post-irradiated cells, complex genomic rearrangements, such as chromoplexy, chromothripsis, and breakage-fusion-bridge cycles, were resulted, indicating the stochastic and chaotic nature of DNA repair in the presence of the massive number of concurrent DNA double-strand breaks. These mutational signatures were confirmed in the genomes of 22 IR-induced secondary malignancies. With high-resolution genomic snapshots of irradiated cells, our findings provide deep insights into how IR-induced DNA damage and subsequent repair processes operate in mammalian cells.

genomics↗

bioRxiv2020

Data-driven multiplexed microtomography of endogenous subcellular dynamics

Simultaneous imaging of various facets of intact biological systems across multiple spatiotemporal scales would be an invaluable tool in biomedicine. However, conventional imaging modalities have stark tradeoffs precluding the fulfilment of all functional requirements. Here we propose the refractive index (RI), an intrinsic quantity governing light-matter interaction, as a means for such measurement. We show that major endogenous subcellular structures, which are conventionally accessed via exogenous fluorescence labeling, are encoded in 3D RI tomograms. We decode this information in a data-driven manner, thereby achieving multiplexed microtomography. This approach inherits the advantages of both high-specificity fluorescence imaging and label-free RI imaging. The performance, reliability, and scalability of this technology have been extensively characterized, and its application within single-cell profiling at unprecedented scales has been demonstrated.

bioengineering↗

bioRxiv2020

Pregnancy success in mice requires appropriate cannabinoid receptor signaling for primary decidua formation

An early event after implantation is stromal cell transformation to decidual cells (decidualization) that support embryo development. In mice, this process begins at the antimesometrial (AM) pole with differentiation of stromal cells into epithelial-like cells (epithelioid cells) surrounding the implantation chamber. This is an avascular zone called the primary decidual zone (PDZ), and considered to function as a transient, size-dependent permeable barrier to protect the embryo from maternal circulating harmful agents, including immunoglobulins, immune cells, microorganisms and other noxious agents. This zone forms on day 5 afternoon and becomes fully established on day 6 with the loss of the crypt epithelium. The PDZ gradually degenerates with the appearance of the secondary decidual zone (SDZ) around the PDZ that peaks on day 8 in mice. Decidualization is critical for early pregnancy in mice and humans. We show that cannabinoid/endocannabinoid signaling influences decidualization in early pregnancy. Mice deficient in two major cannabinoid receptors, CB1 and CB2, show compromised PDZ. We found that angiogenic factors are dysregulated in Cnr1-/-Cnr2-/- mice with defective PDZs, resulting in the abnormal presence of blood vessels and macrophages in this zone; disruption of the PDZ compromises pregnancy outcomes. Using an in vitro decidualization model, we found that Cnr1 levels increase in mouse stromal cells and human uterine fibroblast (Huf) cells undergoing decidualization and that limiting CB1 signaling in these cell types suppresses decidualization in vitro. Since endothelial cells express Cnr2 and decidual cells express Cnr1, we hypothesize that angiogenic events driven by CB2 are integrated with CB1 in decidual cells, leading to proper PDZ formation, a critical step for pregnancy success.

developmental biology↗

bioRxiv2019

Predictive factors for the development of peritumoral brain edema after LINAC-based radiation treatment in patients with intracranial meningioma

Background and purposeDisruption of the tumor-brain barrier in meningioma plays a critical role in the development of peritumoral brain edema (PTBE). We hypothesized that osteoporotic conditions may be associated with PTBE occurrence after radiation in patients with intracranial meningioma. MethodsWe measured Hounsfield units (HU) of the frontal skull on simulation brain CT in patients who underwent linear accelerator (LINAC)-based radiation treatment for intracranial meningioma. Receiver operating characteristic curve analysis was performed to determine the optimal cut-off values for several predictive factors. The cumulative hazard for PTBE was estimated and classified according to these factors. Hazard ratios were then estimated to identify independent predictive factors associated with the development of PTBE after radiation in intracranial meningioma patients. ResultsA total of 83 intracranial meningiomas in 76 patients who received LINAC-based radiation treatment in our hospital over an approximate 5-year period were included for the study. We found mean frontal skull HU [≤]630.625 and gross tumor volume >7.194 cc to be independent predictors of PTBE after radiation treatment in patients with meningioma (hazard ratio, 8.38; P=0.021; hazard ratio, 5.78; P=0.034, respectively). In addition, patients who were [≥]65 years showed a marginally significant association with PTBE. ConclusionsOur study suggests that possible osteoporotic conditions, large tumor volume, and older age may be associated with PTBE occurrence after LINAC-based radiation treatment for intracranial meningioma. In the future we anticipate that these findings may enhance the understanding of the underlying mechanisms of PTBE after radiation in meningioma patients.

neuroscience↗

bioRxiv2019

Vaccination with single plasmid DNA encoding IL-12 and antigens of severe fever with thrombocytopenia syndrome virus elicits complete protection in IFNAR knockout mice

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne disease caused by SFTS virus (SFTSV) infection. Despite a gradual increase of SFTS cases and high mortality in endemic regions, no specific viral therapy nor vaccine is available. Here, we developed a single recombinant plasmid DNA encoding SFTSV genes, Gn and Gc together with NP-NS fusion antigen, as a vaccine candidate. The viral antigens were fused with Fms-like tyrosine kinase-3 ligand (Flt3L) and IL-12 gene was incorporated into the plasmid to enhance cell-mediated immunity. Vaccination with the DNA provides complete protection of IFNAR KO mice upon lethal SFTSV challenge, whereas immunization with a plasmid without IL-12 gene resulted in partial protection. Since we failed to detect antibodies against surface glycoproteins, Gn and Gc, in the immunized mice, antigen-specific cellular immunity, as confirmed by enhanced antigen-specific T cell responses, might play major role in protection. Finally, we evaluated the degree of protective immunity provided by protein immunization of the individual glycoprotein, Gn or Gc. Although both protein antigens induced a significant level of neutralizing activity against SFTSV, Gn vaccination resulted in relatively higher neutralizing activity and better protection than Gc vaccination. However, both antigens failed to provide complete protection. Given that DNA vaccines have failed to induce sufficient immunogenicity in human trials when compared to protein vaccines, optimal combinations of DNA and protein elements, proper selection of target antigens, and incorporation of efficient adjuvant, need to be further investigated for SFTSV vaccine development.\n\nAuthor summarySevere fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infection endemic to East Asia including China, Korea, and Japan. Gradual rise of disease incidence and relatively high mortality have become a serious public health problem in the endemic countries. In this study, we developed a recombinant plasmid DNA encoding four antigens, Gn, Gc, NP, and NS, of SFTS virus (SFTSV) as a vaccine candidate. In order to enhance cell-mediated immunity, the viral antigens were fused with Flt3L and IL-2 gene was incorporated into the plasmid. Immunization with the DNA vaccine provides complete protection against lethal SFTSV infection in IFNAR KO mice. Antigen-specific T cell responses might play a major role in the protection since we observed enhanced T cell responses specific to the viral antigens but failed to detect neutralizing antibody in the immunized mice. When we immunized with either viral glycoprotein, Gn protein induced relatively higher neutralizing activity and better protection against SFTSV infection than Gc antigen, but neither generated complete protection. Therefore, an optimal combination of DNA and protein elements, as well as proper selection of target antigens, might be required to produce an effective SFTSV vaccine.

microbiology↗

bioRxiv2019

Context-dependent activation of SIRT3 is necessary for anchorage-independent survival and metastasis of ovarian cancer cells.

Cells must alter their antioxidant capacity for maximal metastatic potential. However, the antioxidant adaptations required for transcoelomic metastasis, which is the passive dissemination of cancer cells in the peritoneal cavity as seen in ovarian cancer, have largely remained unexplored. Contradicting the need for oxidant scavenging by tumor cells is the observation that expression of the nutrient stress sensor and regulator of mitochondrial antioxidant defenses, SIRT3, is suppressed in many primary tumors. We discovered that this mitochondrial deacetylase is however, upregulated in a context-dependent manner in cancer cells. SIRT3 activity and expression transiently increased following ovarian cancer cell detachment and in tumor cells derived from malignant ascites of high-grade serous adenocarcinoma patients. Mechanistically, SIRT3 prevents mitochondrial superoxide surges in detached cells by regulating the manganese superoxide dismutase SOD2. This mitochondrial stress response is under dual regulation by SIRT3. SIRT3 rapidly increases SOD2 activity as an early adaptation to cellular detachment, which is followed by SIRT3-dependent transcriptional increases in SOD2 during sustained anchorage-independence. In addition, SIRT3 inhibits glycolytic capacity in anchorage-independent cells thereby contributing to metabolic changes in response to detachment. While manipulation of SIRT3 expression has few deleterious effects on cancer cells in attached conditions, SIRT3 up-regulation and SIRT3-mediated oxidant scavenging following matrix detachment are required for anoikis resistance in vitro, and both SIRT3 and SOD2 are necessary for colonization of the peritoneal cavity in vivo. Our results highlight the novel context-specific, pro-metastatic role of SIRT3 in ovarian cancer.

cancer biology↗

bioRxiv2019

Landscape of tumor-infiltrating immune cells in human immunogenic cancers: B cells are inversely associated with CD8T cells, but positively correlated with Treg cells

The composition of tumor-infiltrating immune cells may be a strong predictor of cancer treatment responses and survival outcomes. While B cells have been suggested to suppress T cell cytotoxicity in preclinical studies, it has been less understood whether B cells will exert immune-regulatory roles in human cancers. We explored immune cell landscapes in six human immunogenic cancers, including bladder cancer, head and neck cancer, lung adenocarcinoma, lung squamous cell carcinoma, melanoma, and renal cell carcinoma by calculating gene expression patterns of immune cell-specific metagenes in a total of 2951 cancers. We demonstrated that tumor-infiltrating activated B cells was correlated with regulatory T cell (Treg) infiltration, but had an inverse association with activated CD8 T cell infiltration consistently across all six human cancers. Tumors infiltrated by activated B cells (ActB+ tumors) demonstrated an elevated expression of regulatory cytokines and immune checkpoints, compared to tumors without infiltration by activated B cells (ActB-tumors). Activated B infiltration was not significantly associated with survival outcomes.\n\nPrecisThis human cancer tissue analysis showed that tumor infiltration by activated B cells correlates with decreased infiltration by activated CD8 T cells in immunogenic solid tumors, implicating B cell inhibition may enhance T cell-mediated cytotoxicity.

cancer biology↗

bioRxiv2018

Selection of an Appropriate Empiric Antibiotic Regimen in Culture-Negative Hematogenous Vertebral Osteomyelitis

The aim of this study was to determine which antibiotic combinations are appropriate for culture-negative hematogenous vertebral osteomyelitis (HVO), based on the antibiotic-susceptibility pattern of organisms isolated from cases of culture-proven HVO. We conducted a retrospective chart review of adult patients with microbiologically proven HVO in five tertiary-care hospitals over a 7-year period. The appropriateness of empiric antibiotic regimens was assessed based on the antibiotic susceptibility profiles of isolated bacteria. In total, 358 cases of microbiologically proven HVO were identified. The main causative pathogens identified were methicillin-susceptible Staphylococcus aureus (33.5%), followed by methicillin-resistant S. aureus (MRSA) (24.9%), aerobic gram-negative bacteria (21.8%), and Streptococcus species (11.7%). Extended spectrum {beta}-lactamase (ESBL)-producing Enterobacteriaceae and anaerobes accounted for only 1.7% and 1.4%, respectively, of the causative pathogens. Based on the susceptibility results of isolated organisms, levofloxacin plus rifampicin was appropriate in 73.5%, levofloxacin plus clindamycin in 71.2%, and amoxicillin-clavulanate plus ciprofloxacin in 64.5% of cases. These oral combinations were more appropriate for treating community-acquired HVO (85.8%, 84.0%, and 80.4%, respectively) than healthcare-associated HVO (52.6%, 49.6%, and 37.6%, respectively). Vancomycin combined with ciprofloxacin, ceftriaxone, ceftazidime, or cefepime was similarly appropriate (susceptibility rates of 93.0%, 94.1%, 95.8%, and 95.8%, respectively). In conclusion, in a setting with a high prevalence of MRSA HVO, oral antibiotic combinations may be suboptimal for treatment of culture-negative HVO and should be used only in patients with community-acquired HVO. Vancomycin combined with fluoroquinolone or a broad-spectrum cephalosporin was appropriate in most cases of HVO in this study.

epidemiology↗

bioRxiv2017

In vivo calcium imaging visualizes peripheral neuron sensitization in murine osteoarthritis

ObjectiveThe purpose of this study was to develop a method for analyzing sensory neuron responses to mechanical stimuli in vivo, and to evaluate whether these neuronal responses change after destabilization of the medial meniscus (DMM).\n\nMethodsDMM or sham surgery was performed in 10-week old male C57BL/6 wild-type or Pirt-GCaMP3+/- mice. All experiments were performed eight weeks after surgery. Knee and hind paw hyperalgesia were assessed in wild-type mice. The retrograde label DiI was injected into the ipsilateral knee to quantify the number of knee-innervating neurons in the L4 dorsal root ganglion (DRG) in wild-type mice. In vivo calcium imaging was performed on the ipsilateral L4 DRG of Pirt-GCaMP3+/- mice as mechanical stimuli (paw pinch, knee pinch, knee twist) were applied to the ipsilateral hind limb.\n\nResultsEight weeks after surgery, DMM mice had more hyperalgesia in the knee and hind paw compared to sham mice. Intra-articular injection of DiI labeled similar numbers of neurons in the L4 DRG of sham and DMM mice. Increased numbers of sensory neurons responded to all three mechanical stimuli in DMM mice, as assessed by in vivo calcium imaging. The majority of responses in sham and DMM mice were in small-to-medium-sized neurons, consistent with the size of nociceptors. The magnitude of responses was similar between sham and DMM mice.\n\nConclusionsWe demonstrated that increased numbers of small-to-medium sized DRG neurons respond to mechanical stimuli 8 weeks after DMM surgery, suggesting that nociceptors have become sensitized by lowering the response threshold.

neuroscience↗