Measurements of All-Particle Energy Spectrum and Mean Logarithmic Mass of Cosmic Rays from 0.3 to 30 PeV with LHAASO-KM2A

We present the measurements of all-particle energy spectrum and mean logarithmic mass of cosmic rays in the energy range of 0.3-30 PeV using data collected from LHAASO-KM2A between September 2021 and December 2022, which is based on a nearly composition-independent energy reconstruction method, achieving unprecedented accuracy. Our analysis reveals the position of the knee at 3.67±0.05±0.15  PeV. Below the knee, the spectral index is found to be -2.7413±0.0004±0.0050, while above the knee, it is -3.128±0.005±0.027, with the sharpness of the transition measured with a statistical error of 2%. The mean logarithmic mass of cosmic rays is almost heavier than helium in the whole measured energy range. It decreases from 1.7 at 0.3 PeV to 1.3 at 3 PeV, representing a 24% decline following a power law with an index of -0.1200±0.0003±0.0341. This is equivalent to an increase in abundance of light components. Above the knee, the mean logarithmic mass exhibits a power law trend towards heavier components, which is reversal to the behavior observed in the all-particle energy spectrum. Additionally, the knee position and the change in power-law index are approximately the same. These findings suggest that the knee observed in the all-particle spectrum corresponds to the knee of the light component, rather than the medium-heavy components.

Measurement of Ultra-High-Energy Diffuse Gamma-Ray Emission of the Galactic Plane from 10 TeV to 1 PeV with LHAASO-KM2A

The diffuse Galactic γ-ray emission, mainly produced via interactions between cosmic rays and the interstellar medium and/or radiation field, is a very important probe of the distribution, propagation, and interaction of cosmic rays in the Milky Way. In this Letter, we report the measurements of diffuse γ rays from the Galactic plane between 10 TeV and 1 PeV energies, with the square kilometer array of the Large High Altitude Air Shower Observatory (LHAASO). Diffuse emissions from the inner (15°10  TeV). The energy spectrum in the inner Galaxy regions can be described by a power-law function with an index of -2.99±0.04, which is different from the curved spectrum as expected from hadronic interactions between locally measured cosmic rays and the line-of-sight integrated gas content. Furthermore, the measured flux is higher by a factor of ∼3 than the prediction. A similar spectrum with an index of -2.99±0.07 is found in the outer Galaxy region, and the absolute flux for 10≲E≲60  TeV is again higher than the prediction for hadronic cosmic ray interactions. The latitude distributions of the diffuse emission are consistent with the gas distribution, while the longitude distributions show clear deviation from the gas distribution. The LHAASO measurements imply that either additional emission sources exist or cosmic ray intensities have spatial variations.

Single cell landscape of parietal epithelial cells in healthy and diseased states

The biology and diversity of glomerular parietal epithelial cells (PECs) are important for understanding podocyte regeneration and crescent formation. Although protein markers have revealed the morphological heterogeneity of PECs, the molecular characteristics of PEC subpopulations remain largely unknown. Here, we performed a comprehensive analysis of PECs using single-cell RNA sequencing (scRNA-seq) data. Our analysis identified five distinct PEC subpopulations: PEC-A1, PEC-A2, PEC-A3, PEC-A4 and PEC-B. Among these subpopulations, PEC- A1 and PEC-A2 were characterized as podocyte progenitors while PEC-A4 represented tubular progenitors. Further dynamic signaling network analysis indicated that activation of PEC-A4 and the proliferation of PEC-A3 played pivotal roles in crescent formation. Analyses suggested that upstream signals released by podocytes, immune cells, endothelial cells and mesangial cells serve as pathogenic signals and may be promising intervention targets in crescentic glomerulonephritis. Pharmacological blockade of two such pathogenic signaling targets, proteins Mif and Csf1r, reduced hyperplasia of the PECs and crescent formation in anti-glomerular basement membrane glomerulonephritis murine models. Thus, our study demonstrates that scRNA-seq-based analysis provided valuable insights into the pathology and therapeutic strategies for crescentic glomerulonephritis.

A tera-electron volt afterglow from a narrow jet in an extremely bright gamma-ray burst

Some gamma-ray bursts (GRBs) have a tera-electron volt (TeV) afterglow, but the early onset of this has not been observed. We report observations with the Large High Altitude Air Shower Observatory of the bright GRB 221009A, which serendipitously occurred within the instrument field of view. More than 64,000 photons >0.2 TeV were detected within the first 3000 seconds. The TeV flux began several minutes after the GRB trigger, then rose to a peak about 10 seconds later. This was followed by a decay phase, which became more rapid ~650 seconds after the peak. We interpret the emission using a model of a relativistic jet with half-opening angle ~0.8°. This is consistent with the core of a structured jet and could explain the high isotropic energy of this GRB.

Constraints on Heavy Decaying Dark Matter from 570 Days of LHAASO Observations

The kilometer square array (KM2A) of the large high altitude air shower observatory (LHAASO) aims at surveying the northern γ-ray sky at energies above 10 TeV with unprecedented sensitivity. γ-ray observations have long been one of the most powerful tools for dark matter searches, as, e.g., high-energy γ rays could be produced by the decays of heavy dark matter particles. In this Letter, we present the first dark matter analysis with LHAASO-KM2A, using the first 340 days of data from 1/2-KM2A and 230 days of data from 3/4-KM2A. Several regions of interest are used to search for a signal and account for the residual cosmic-ray background after γ/hadron separation. We find no excess of dark matter signals, and thus place some of the strongest γ-ray constraints on the lifetime of heavy dark matter particles with mass between 10^{5} and 10^{9}  GeV. Our results with LHAASO are robust, and have important implications for dark matter interpretations of the diffuse astrophysical high-energy neutrino emission.

Exploring Lorentz Invariance Violation from Ultrahigh-Energy γ Rays Observed by LHAASO

Recently, the LHAASO Collaboration published the detection of 12 ultrahigh-energy γ-ray sources above 100 TeV, with the highest energy photon reaching 1.4 PeV. The first detection of PeV γ rays from astrophysical sources may provide a very sensitive probe of the effect of the Lorentz invariance violation (LIV), which results in decay of high-energy γ rays in the superluminal scenario and hence a sharp cutoff of the energy spectrum. Two highest energy sources are studied in this work. No signature of the existence of the LIV is found in their energy spectra, and the lower limits on the LIV energy scale are derived. Our results show that the first-order LIV energy scale should be higher than about 10^{5} times the Planck scale M_{Pl} and that the second-order LIV scale is >10^{-3}M_{Pl}. Both limits improve by at least one order of magnitude the previous results.

COVID-19 prevention measures reduce dengue spread in Yunnan Province, China, but do not reduce established outbreak

The COVID-19 pandemic and measures against it provided a unique opportunity to understand the transmission of other infectious diseases and to evaluate the efficacy of COVID-19 prevention measures on them. Here we show a dengue epidemic in Yunnan, China, during the pandemic of COVID-19 was dramatically reduced compared to non-pandemic years and, importantly, spread was confined to only one city, Ruili. Three key features characterized this dengue outbreak: (i) the urban-to-suburban spread was efficiently blocked; (ii) the scale of epidemic in urban region was less affected; (iii) co-circulation of multiple strains was attenuated. These results suggested that countermeasures taken during COVID-19 pandemic are efficient to prevent dengue transmission between cities and from urban to suburban, as well to reduce the co-circulation of multiple serotypes or genotypes. Nevertheless, as revealed by the spatial analysis, once the dengue outbreak was established, its distribution was very stable and resistant to measures against COVID-19, implying the possibility to develop a precise prediction method.

1-Hydroxypyrene mediates renal fibrosis through aryl hydrocarbon receptor signalling pathway

BACKGROUND AND PURPOSE

In chronic kidney disease (CKD), patients inevitably reach end-stage renal disease and require renal transplant. Evidence suggests that CKD is associated with metabolite disorders. However, the molecular pathways targeted by metabolites remain enigmatic. Here, we describe roles of 1-hydroxypyrene in mediating renal fibrosis.

EXPERIMENTAL APPROACH

We analysed 5406 urine and serum samples from patients with Stage 1-5 CKD using metabolomics, and 1-hydroxypyrene was identified and validated using longitudinal and drug intervention cohorts as well as 5/6 nephrectomised and adenine-induced rats.

KEY RESULTS

We identified correlations between the urine and serum levels of 1-hydroxypyrene and the estimated GFR in patients with CKD onset and progression. Moreover, increased 1-hydroxypyrene levels in serum and kidney tissues correlated with decreased renal function in two rat models. Up-regulated mRNA expression of aryl hydrocarbon receptor and its target genes, including CYP1A1, CYP1A2 and CYP1B1, were observed in patients and rats with progressive CKD. Further we showed up-regulated mRNA expression of aryl hydrocarbon receptor and its three target genes, plus up-regulated nuclear aryl hydrocarbon receptor protein levels in mice and HK-2 cells treated with 1-hydroxypyrene, which caused accumulation of extracellular matrix components. Treatment with aryl hydrocarbon receptor short hairpin RNA or flavonoids inhibited mRNA expression of aryl hydrocarbon receptor and its target genes in 1-hydroxypyrene-induced HK-2 cells and mice.

CONCLUSION AND IMPLICATIONS

Metabolite 1-hydroxypyrene was demonstrated to mediate renal fibrosis through activation of the aryl hydrocarbon receptor signalling pathway. Targeting aryl hydrocarbon receptor may be an alternative therapeutic strategy for CKD progression.

Epidemiological and clinical characteristics of the chikungunya outbreak in Ruili City, Yunnan Province, China

Chikungunya fever is an acute infectious disease caused by the chikungunya virus (CHIKV) that is characterized by fever, rash, and joint pain. CHIKV has infected millions of people in Africa, Asia, America, and Europe since it re-emerged in the Indian Ocean region in 2004. Here, we report an outbreak of Chikungunya fever that occurred in Ruili of Yunnan Province, a city located on the border between China and Myanmar, in September 2019. The outbreak lasted for three months from September to December. Overall, 112 cases were confirmed by a real-time reverse-transcription polymerase chain reaction in the Ruili People's Hospital, and they showed apparent temporal, spatial, and population aggregation. Among them, 91 were local cases distributed in 19 communities of Ruili City, and 21 were imported cases. The number of female patients was higher than that of male patients, and most patients were between 20 and 60 years old. The main clinical manifestations included joint pain (91.96%), fever (86.61%), fatigue (58.04%), chills (57.14%), rash (48.21%), headache (39.29%), and so forth. Biochemical indexes revealed increased C-reactive protein (63.39%), lymphopenia (57.17%), increased hemoglobin (33.04%), neutrophilia (28.57%), and thrombocytopenia (16.07%). Phylogenetic analysis of the complete sequences indicated that the CHIKV strains in this outbreak belonged to the Indian Ocean clade of the East/Central/South African genotype. We speculated that this chikungunya outbreak might be caused by CHIKV-infected persons returning from Myanmar, and provided a reference for the formulation of effective treatment and prevention measures.

Peta-electron volt gamma-ray emission from the Crab Nebula

The Crab Nebula is a bright source of gamma rays powered by the Crab Pulsar's rotational energy through the formation and termination of a relativistic electron-positron wind. We report the detection of gamma rays from this source with energies from 5 × 10^-4 to 1.1 peta-electron volts with a spectrum showing gradual steepening over three energy decades. The ultrahigh-energy photons imply the presence of a peta-electron volt electron accelerator (a pevatron) in the nebula, with an acceleration rate exceeding 15% of the theoretical limit. We constrain the pevatron's size between 0.025 and 0.1 parsecs and the magnetic field to ≈110 microgauss. The production rate of peta-electron volt electrons, 2.5 × 10³⁶ ergs per second, constitutes 0.5% of the pulsar spin-down luminosity, although we cannot exclude a contribution of peta-electron volt protons to the production of the highest-energy gamma rays.

Extended Very-High-Energy Gamma-Ray Emission Surrounding PSR J0622+3749 Observed by LHAASO-KM2A

We report the discovery of an extended very-high-energy (VHE) gamma-ray source around the location of the middle-aged (207.8 kyr) pulsar PSR J0622+3749 with the Large High-Altitude Air Shower Observatory (LHAASO). The source is detected with a significance of 8.2σ for E>25  TeV assuming a Gaussian template. The best-fit location is (right ascension, declination) =(95.47°±0.11°,37.92°±0.09°), and the extension is 0.40°±0.07°. The energy spectrum can be described by a power-law spectrum with an index of -2.92±0.17_{stat}±0.02_{sys}. No clear extended multiwavelength counterpart of the LHAASO source has been found from the radio to sub-TeV bands. The LHAASO observations are consistent with the scenario that VHE electrons escaped from the pulsar, diffused in the interstellar medium, and scattered the interstellar radiation field. If interpreted as the pulsar halo scenario, the diffusion coefficient, inferred for electrons with median energies of ∼160  TeV, is consistent with those obtained from the extended halos around Geminga and Monogem and much smaller than that derived from cosmic ray secondaries. The LHAASO discovery of this source thus likely enriches the class of so-called pulsar halos and confirms that high-energy particles generally diffuse very slowly in the disturbed medium around pulsars.

Ultrahigh-energy photons up to 1.4 petaelectronvolts from 12 γ-ray Galactic sources

The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 10¹⁵ electronvolts) indicates the existence of the so-called PeVatrons-cosmic-ray factories that accelerate particles to PeV energies. We need to locate and identify such objects to find the origin of Galactic cosmic rays¹. The principal signature of both electron and proton PeVatrons is ultrahigh-energy (exceeding 100 TeV) γ radiation. Evidence of the presence of a proton PeVatron has been found in the Galactic Centre, according to the detection of a hard-spectrum radiation extending to 0.04 PeV (ref. ²). Although γ-rays with energies slightly higher than 0.1 PeV have been reported from a few objects in the Galactic plane^3-6, unbiased identification and in-depth exploration of PeVatrons requires detection of γ-rays with energies well above 0.1 PeV. Here we report the detection of more than 530 photons at energies above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy γ-ray sources with a statistical significance greater than seven standard deviations. Despite having several potential counterparts in their proximity, including pulsar wind nebulae, supernova remnants and star-forming regions, the PeVatrons responsible for the ultrahigh-energy γ-rays have not yet been firmly localized and identified (except for the Crab Nebula), leaving open the origin of these extreme accelerators.

Activated NF-κB/Nrf2 and Wnt/β-catenin pathways are associated with lipid metabolism in CKD patients with microalbuminuria and macroalbuminuria

Early diagnosis of CKD patients at risk for microalbuminuria or macroalbuminuria could facilitate clinical outcomes and long-term survival. Considering the few and limited efficacy of current biomarkers in early detection, we aim to discover plasma lipids that effectively predict the development of CKD paitents with microalbuminuria or macroalbuminuria. A total of 380 healthy controls and 1156 patients with CKD stages 3 to 5 were stratified by urine albumin-creatinine ratio as microalbuminuria (30-300 mg/g) and macroalbuminuria (>300 mg/g). Fasting plasma samples were determined by UPLC-HDMS based on lipidomics. Quantitative real-time polymerase chain reaction, Western blot and immunohistochemical analyses were used to validate the lipid metabolism-associated pathways. Pathway analysis demonstrated that these lipids were closely associated with PPARγ, inflammatory mediator regulation of TRP channels and RAS signaling, which were intimately involved in activated NF-κB and Nrf2 pathways. We further carried out pathway validation and demonstrated that NF-κB pathway was activated in patients with macroalbuminuria compared with CKD patients with microalbuminuria, while Nrf2-associated protein expression was downregulated, which was accompanied by the up-regulation of Wnt/β-catenin signaling pathway. Four lipids including DTA, 5,8-TDA, GGD3 and DHA that showed great potential in the discrimination of CKD patients with microalbuminuria and healthy controls were selected by logistic regression analysis. Additionally, six lipid species including CDCA, glucosylceramide, GGD2, TTA, DHA and EDA that contributed to the discrimination of CKD patients with microalbuminuria and macroalbuminuria were selected by logistic LASSO regression Gangliosides were first identified and might be promising therapeutic targets for CKD patients with the different degree of albuminuria. Collectively, this study first demonstrates the association of plasma inflammation, oxidative stress, Wnt/β-catenin and lipid metabolism in CKD patients with microalbuminuria and macroalbuminuria.

Identification of serum metabolites associating with chronic kidney disease progression and anti-fibrotic effect of 5-methoxytryptophan

Early detection and accurate monitoring of chronic kidney disease (CKD) could improve care and retard progression to end-stage renal disease. Here, using untargeted metabolomics in 2155 participants including patients with stage 1–5 CKD and healthy controls, we identify five metabolites, including 5-methoxytryptophan (5-MTP), whose levels strongly correlate with clinical markers of kidney disease. 5-MTP levels decrease with progression of CKD, and in mouse kidneys after unilateral ureteral obstruction (UUO). Treatment with 5-MTP ameliorates renal interstitial fibrosis, inhibits IκB/NF-κB signaling, and enhances Keap1/Nrf2 signaling in mice with UUO or ischemia/reperfusion injury, as well as in cultured human kidney cells. Overexpression of tryptophan hydroxylase-1 (TPH-1), an enzyme involved in 5-MTP synthesis, reduces renal injury by attenuating renal inflammation and fibrosis, whereas TPH-1 deficiency exacerbates renal injury and fibrosis by activating NF-κB and inhibiting Nrf2 pathways. Together, our results suggest that TPH-1 may serve as a target in the treatment of CKD.

Accurate monitoring of chronic kidney disease (CKD) progression is essential for efficient disease management. Here Chen et al. identify five serum metabolites in patients with stage 1–5 CKD whose levels associate with disease progression, and find that 5-methoxytryptophan and its regulatory enzyme TPH-1 exert anti-fibrotic effects in mouse models of kidney injury.

Therapeutic Role of Tangshenkang Granule () in Rat Model with Diabetic Nephropathy

OBJECTIVE

To evaluate the renal protective effect of Tangshenkang Granule () in a rat model of diabetic nephropathy (DN).

METHODS

Forty male Sprague-Dawley rats were randomly divided into control, DN, Tangshenkang and benazepril groups. DN model was established in the rats of DN, Tangshenkang and benazepril groups. Tangshenkang Granule solution and benazepril hydrochloride solution were intragastrically administered daily to the rats in the Tangshenkang and benazepril groups for 8 weeks, respectively. Urinary albumin and creatinine were detected. The albumin/creatinine (ACR) was calculated in addition to 24 h urinary protein (24-h UPr), serum creatinine (Scr), blood urea nitrogen (BUN), total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), and creatinine clearance rate (Ccr). Right kidneys were harvested for pathological observation using periodic acid-silver methenamine-Masson staining. The average glomerular diameter (DG), average glomerular (AG) and mesangial areas (AM) were measured. The thickness of glomerular basement membrane (TGBM) was detected using transmission electron microscope.

RESULTS

Compared with rats in the control group, rats in the DN group showed significantly decreased body weight, increased hypertrophy index, 24-h urinary volume, 24-h UPr, ACR, Scr, BUN, Ccr, blood lipids as well as renal pathological indices including DG, AG, AM, AM/AG and TGBM (P <0.05). Compared with the DN group, the weights of rats in the Tangshenkang and benazepril groups were significantly increased, and the renal hypertrophy indices were significantly decreased (P <0.05). The 24-h urinary volumes, ACR, 24-h UPr, Scr, BUN, Ccr, LDL, DG, AG, AM and TGBM were obviously decreased (P <0.05). Compared with the benazepril group, the Tangshenkang group showed significantly decreased levels of ACR, 24-h UPr, AG and AM (P <0.05).

CONCLUSIONS

Tangshenkang Granule decreased the urinary protein, attenuated the high glomerular filtration rate and improved lipid metabolism in DN rats, and prevented further injury induced by diabetic nephropathy.

Metabolomic Signatures of Chronic Kidney Disease of Diverse Etiologies in the Rats and Humans

Chronic kidney disease (CKD) has emerged as a major public health problem worldwide. It frequently progresses to end-stage renal disease, which is related to very high cost and mortality. Novel biomarkers can provide insight into the novel mechanism, facilitate early detection, and monitor progression of CKD and its response to therapeutic interventions. To identify potential biomarkers, we applied an UPLC-HDMS together with univariate and multivariate statistical analyses using plasma samples from patients with CKD of diverse etiologies (100 sera in discovery set and 120 sera in validation set) and two different rat models of CKD. Using comprehensive screening and validation workflow, we identified a panel of seven metabolites that were shared by all patients and animals regardless of the underlying cause of CKD. These included ricinoleic acid, stearic acid, cytosine, LPA(16:0), LPA(18:2), 3-methylhistidine, and argininic acid. The combination of these seven biomarkers enabled the discrimination of patients with CKD from healthy subjects with a sensitivity of 83.3% and a specificity of 96.7%. In addition, these biomarkers accurately reflected improvements in renal function in response to the therapeutic interventions. Our results indicated that the identified biomarkers may improve the diagnosis of CKD and provide a novel tool for monitoring of the progression of disease and response to treatment in CKD patients.

Metabolomics insights into activated redox signaling and lipid metabolism dysfunction in chronic kidney disease progression

Early detection is critical in prevention and treatment of kidney disease. However currently clinical laboratory and histopathological tests do not provide region-specific and accurate biomarkers for early detection of kidney disease. The present study was conducted to identify sensitive biomarkers for early detection and progression of tubulo-interstitial nephropathy in aristolochic acid I-induced rats at weeks 4, 8 and 12. Biomarkers were validated using aristolochic acid nephropathy (AAN) rats at week 24, adenine-induced chronic kidney disease (CKD) rats and CKD patients. Compared with control rats, AAN rats showed anemia, increased serum urea and creatinine, progressive renal interstitial fibrosis, activation of nuclear factor-kappa B, and up-regulation of pro-inflammatory, pro-oxidant, and pro-fibrotic proteins at weeks 8 and 12. However, no significant difference was found at week 4. Metabolomics identified 12-ketodeoxycholic acid, taurochenodesoxycholic acid, LPC(15:0) and docosahexaenoic acid as biomarkers for early detection of tubulo-interstitial nephropathy. With prolonging aristolochic acid I exposure, LPE(20:2), cholic acid, chenodeoxycholic acid and LPC(17:0) were identified as biomarkers for progression from early to advanced AAN and lysoPE(22:5), indoxyl sulfate, uric acid and creatinine as biomarkers of advanced AAN. These biomarkers were reversed by treatment of irbesartan and ergone in AAN rats at week 24 and adenine-induced CKD rats. In addition, these biomarkers were also reversed by irbesartan treatment in CKD patients.

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Tubulo-interstitial nephropathy (TIN) is a common cause of chronic kidney disease.

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Plasma biomarker discovery and validation was performed by UPLC-based metabolomics.

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CKD progression associated with activated redox signaling and lipid dysfunction.

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TIN was associated with abnormal amino acids, purine and phospholipid metabolisms.

Ergosta-4,6,8(14),22-tetraen-3-one isolated from Polyporus umbellatus prevents early renal injury in aristolochic acid-induced nephropathy rats

Objectives

Aristolochic acid (AA) nephropathy, first reported as Chinese herbs nephropathy, is a rapidly progressive tubulointerstitial nephropathy that results in severe anemia, interstitial fibrosis and end-stage renal disease. Tubulointerstitial injury was studied in a rat model of AA nephropathy to determine whether ergosta-4,6,8(14),22-tetraen-3-one (ergone) treatment prevents early renal injury in rats with aristolochic acid I-induced nephropathy.

Methods

Early renal injury via renal interstitial fibrosis was induced in rats by administration of aristolochic acid I (AAI) solution intragastrically for 8 weeks. Ninety-six rats were randomly divided into four groups (n = 24/group): (1) control (2) AAI (3) AAI + ergone (10 mg/kg) and (4) AAI + ergone (20 mg/kg). Blood and urine samples were collected and rat were sacrificed for histological assessment of the kidneys on at the end of weeks 2, 4, 6 and 8.

Key findings

AAI caused progressive elevation of blood urea nitrogen, creatinine, potassium, sodium, chlorine, proteinuria and urinary N-acetyl-β-D-glucosaminidase (NAG). Ergone suppressed elevation of blood urea, nitrogen, creatinine, proteinuria and urinary NAG to some degree, but the AAI–ergone-treated group did not differ from AAI-treated group for body weight, serum potassium, sodium and chlorine. The progress of the lesions in the kidney after AAI administration was also observed by histopathological examinations, but kidneys from rats of AAI–ergone-treated group displayed fewer lesions.

Conclusions

Ergone treatment conferred protection against early renal injury in a rat model of AA nephropathy. Early administration of ergone may prevent the progression of renal injury and the subsequent renal fibrosis in AA nephropathy.

In vivo production of oligodeoxyribonucleotides of specific sequences: application to antisense DNA

Retrons, bacterial retroelements found in Gram-negative bacteria, are integrated into the bacterial genome expressing a reverse transcriptase related to eukaryotic reverse transcriptase. The bacterial reverse transcriptases are responsible for the production of multicopy, single-stranded (ms) DNA consisting of a short single-stranded DNA that is attached to an internal guanosine residue of an RNA molecule by a 2',5'-phosphodiester linkage. Reverse transcriptases use an RNA transcript from the retrons, not only as primer, but also as template for msDNA synthesis. By studying the structural requirement, it was found that for msDNA synthesis an internal region of msDNA can be replaced with other sequences. msDNA can thus be used as a vector for in vivo production of an oligodeoxyribonucleotide of a specific sequence. Artificial msDNAs containing a sequence complementary to part of the mRNA for the major outer membrane lipoprotein of Escherichia coli effectively inhibited lipoprotein biosynthesis upon induction of msDNA synthesis. This is the first demonstration of in vivo synthesis of oligodeoxyribonucleotides having antisense function. Since we have previously demonstrated that bacterial retrons are functional in eukaryotes producing msDNA in yeast and in mouse NIH/3T3 fibroblasts, the present system may also be used to produce a specific oligodeoxyribonucleotide inside the cells to regulate eukaryotic gene expression artificially. We also describe a method to produce cDNA to a specific cellular mRNA using the retron system.

msDNA-Ec48, the smallest multicopy single-stranded DNA from Escherichia coli

Previously we have reported a novel bacterial reverse transcriptase (RT) from Escherichia coli ECOR58 strains in which the YXDD box was replaced with LVDD (J.-R. Mao, S. Inouye, and M. Inouye, Biochem. Biophys. Res. Commun. 227:489-493, 1996). Here we determined the structure of the multicopy single-stranded DNA (msDNA) produced by the RT. The msDNA was found to consist of a single-stranded DNA of 48 nucleotides in length, the shortest msDNA thus far identified from natural sources. The msDNA, the RT, and the retron are designated msDNA-Ec48, RT-Ec48, and retron-Ec48, respectively. On the basis of the structure of the msr gene, the RNA molecule of msDNA-Ec48 is predicted to be composed of 119 ribonucleotides; it is the longest RNA among the known msDNAs. Analysis of the DNA sequences flanking the retron indicates that retron-Ec48 is associated with a prophage related to phages P2 and P4.

Enhancement of frame-shift mutation by the overproduction of msDNA in Escherichia coli

A minor population of wild Escherichia coli strains contain retroelements called retrons, which produce a peculiar satellite DNA, multicopy single-stranded DNA (msDNA). It has been reported that mismatched base pairs in the secondary structure formed in msDNA are mutagenic in E. coli[Maas et al.(1994) Mol.Microbiol. 14,437-441; Maas et al. (1996) Mol. Microbiol, 19, 505-509]. We reexamined this proposal by converting mismatched base pairs to matched base pairs using a single msDNA species, msDNA-Ec86, or by deleting mismatched regions using msDNA-Ec73. We also examined the effect of reverse transcriptases (RT) without msDNA production on mutagenesis. All the constructs are under the lpp/lac promoter-operator control so that their mutagenic effects can be tested in the absence and the presence of a lac inducer. It was found that when the production of msDNA-Ec86 or Ec73 was induced, reversion frequencies from Lac- to Lac+ significantly increased in the case of a Lac- mutation caused by a frame-shift mutation, but much less by a substitution mutation. The removal of mismatched base pairs eliminated the high mutation frequencies, and the inducible expression of RT alone was not mutagenic. These results are consistent with the hypothesis of Maas and his associates that mismatched base pairs in msDNA sequester a cellular mismatch repair system, resulting in the increase of frame-shift mutations.

An unusual bacterial reverse transcriptase having LVDD in the YXDD box from Escherichia coli

A minor population of wild strains of Escherichia coli contains a gene for reverse transcriptase (RT) which is responsible for the synthesis of multicopy single-stranded DNA (msDNA), a branched DNA-RNA complex. A DNA fragment capable of synthesizing msDNA was cloned from strain ECOR-58, one of the 72 wild strains in the ECOR collection. The complete open reading frame of a novel reverse transcriptase, designated ECOR-58 RT, was identified. ECOR-58 RT consisted of 408 amino acid residues, and its 227-residue polymerase domain from residue 43 to 269 showed significant homologies to all the other bacterial RTs so far identified. Most significantly, its YXDD box, the most highly conserved sequence in all RTs from prokaryotes to eukaryotes, was found to be replaced with LVDD. ECOR-58 RT was found to be most distantly related in a phylogenetic tree to all 9 other bacterial RTs so far identified.

Gene regulation by antisense DNA produced in vivo

Antisense technology has been widely used for regulating gene expression. Single-stranded RNA or DNA complementary to a target mRNA can inhibit the translation of the mRNA. Antisense RNA is produced in vivo, while antisense DNA is chemically synthesized as an oligonucleotide, which is extracellularly added to the cells. To maintain the effect of antisense DNA, a synthetic oligonucleotide has to be constantly added to the system. An advantage of antisense DNA over antisense RNA is that the target mRNA hybridized with the antisense DNA can be specifically digested by ribonuclease H. Here, we attempted to produce in vivo short single-stranded DNAs complementary to a specific mRNA. We demonstrate that such antisense oligodeoxyribonucleotide of a desired sequence can be produced in Escherichia coli using a retron, a bacterial retroelement, as a vector and that the antisense DNA thus produced in vivo can effectively inhibit the expression of a specific E. coli gene, such as the gene for the major outer membrane lipoprotein.

Regional changes in spinal cord glucose metabolism in a rat model of painful neuropathy

Spinal cord patterns of metabolic activity in a model of neuropathic pain were assessed in unanesthetized rats by the [14C]-2-deoxyglucose (2-DG) technique. Rats used in this procedure had demonstrable thermal hyperalgesia ipsilateral to sciatic nerve ligation and ipsilateral hindpaws that were lifted in a guarded position. The latter indicated possible spontaneous pain. Sciatic nerve ligation produced significant increases in glucose utilization in the dorsal and ventral horns of both sides, with greater activity present on the ipsilateral as compared to the contralateral side. Peak activity was in laminae V-VI, a region involved in nociceptive processing. Thus, a chronic increase in neuronal activity in these regions may reflect spontaneous neuropathic pain.

Changes of reactions of neurones in dorsal raphe nucleus and locus coeruleus to electroacupuncture by hypothalamic arcuate nucleus stimulation

In this experiment the role of the hypothalamic arcuate nucleus (ARC) in acupuncture analgesia and its mechanisms were studied with behavioural and electrophysiological methods. After ARC stimulation the analgesic effect of acupuncture was enhanced significantly and the responses of neurones to electroacupuncture were increased in the dorsal raphe nucleus (DR) and reduced in the locus coeruleus (LC), which could be reversed by intraperitoneal injection of naloxone. The results indicate that ARC might participate in acupuncture analgesia via changing the responses of DR and LC neurones to electroacupuncture, a process in which opiate-like substances (probably beta-endorphin) are involved.