β-Arrestin-2 modulates radiation-induced intestinal crypt progenitor/stem cell injury

Intestinal crypt progenitor/stem (ICPS) cell apoptosis and vascular endothelial cell apoptosis are responsible for the initiation and development of ionizing radiation (IR)-evoked gastrointestinal syndrome. The signaling mechanisms underlying IR-induced ICPS cell apoptosis remain largely unclear. Our findings provide evidence that β-arrestin-2 (βarr2)-mediated ICPS cell apoptosis is crucial for IR-stimulated intestinal injury. βArr2-deficient mice exhibited decreased ICPS cell and intestinal Lgr5⁺ (leucine-rich repeat-containing G-protein-coupled receptor 5-positive) stem cell apoptosis, promoted crypt proliferation and reproduction, and protracted survival following lethal doses of radiation. Radioprotection in the ICPS cells isolated from βarr2-deficient mice depended on prolonged nuclear factor-κB (NF-κB) activation via direct interaction of βarr2 with IκBα and subsequent inhibition of p53-upregulated modulator of apoptosis (PUMA)-mediated mitochondrial dysfunction. Unexpectedly, βarr2 deficiency had little effect on IR-induced intestinal vascular endothelial cell apoptosis in mice. Consistently, βarr2 knockdown also provided significant radioresistance by manipulating NF-κB/PUMA signaling in Lgr5⁺ cells in vitro. Collectively, these observations show that targeting the βarr2/NF-κB/PUMA novel pathway is a potential radiomitigator for limiting the damaging effect of radiotherapy on the gastrointestinal system. Significance statement: acute injury to the intestinal mucosa is a major dose-limiting complication of abdominal radiotherapy. The issue of whether the critical factor for the initiation of radiation-induced intestinal injury is intestinal stem cell apoptosis or endothelial cell apoptosis remains unresolved. βArrs have recently been found to be multifunctional adaptor of apoptosis. Here, we found that β-arrestin-2 (βarr2) deficiency was associated with decreased radiation-induced ICPS cell apoptosis, which prolonged survival in abdominally irradiated mice. Moreover, βarr2 deficiency-mediated intestinal progenitor/stem cell radioprotection relied on protracted NF-κB activation and subsequent suppression of PUMA induction. Our results suggest that ICPS cell apoptosis is the factor involved in the initiation and development of radiation-induced gastrointestinal syndrome. βArr2 is a potential target for lessening radiation-induced ICPS cell apoptosis.

[Effects of job content on psychological stress in young recruits]

OBJECTIVE

To explore the effects of job content on psychological stress in young recruits.

METHODS

In October 2014, 625 young recruits enrolled in one troop of Xinjiang Military Command in 2014 were chosen as subjects by multi-stage stratified random sampling. The Chinese version of the job content questionnaire (JCQ)and the psychological stress self evaluation test (PEST)were used to investigate the subjects. The subjects were divided into two groups with scores higher and lower than the mean score of three subscales (job requirement, degree of autonomy, and social support)of JCQ to explore the effects of job content on psychological stress in young recruits. The correlation of psychological stress with three subscales of job content was evaluated using the Pearson' s correlation analysis. Binary logistic regression analysis was used to analyze the influencing factors for psychological stress.

RESULTS

The PEST score of young recruits was 49.98±9.98. Forty-five (7.68%)out of them had scores of ≥70 points and were diagnosed with high levels of psychological stress. When the subjects were grouped based on socio-demographic characteristics, a high level of psychological stress was significantly more frequent in subjects less than 20 years of age than in those not less than 20 years of age, in smoking subjects than in non-smoking subjects, and in urban residents than in rural residents (10.42% vs 5.03%, P<0.05; 10.14% vs 5.33%, P<0.05; 10.85% vs 5.88% , P <0.05). There were no significant differences in educational level or identity before recruitment between subjects with different levels of psychological stress (P>0.05). In various job content domains that had impacts on psychological stress, subjects with a low score of social support had significantly higher PEST scores than those with a high score of social support (50.96±10.35 vs 48.49±9.22, P<0.01). The PEST score was negatively correlated with the degree of autonomy and social support (r=-0.103, P<0.05; r=-0.239, P<0.05). The results of logistic regression analysis showed that job requirement and social support were influencing factors for psychological stress (OR=0.718, 95% CI= 0.718 (0.607~0.851), P<0.05; OR=1.185, 95% CI=1.185 (1.087~1.292), P<0.05).

CONCLUSION

Psychological stress of young recruits in army is not optimistic. Psychological stress is weakly negatively correlated with social support. The low scores on job requirement subscale and social support subscale may be potential protective factor and risk factor for psychological stress, respectively.

Association Between Interleukin-2 -330 T/G Polymorphism and Acute Renal Graft Rejection: A Meta-analysis

BACKGROUND

Interleukin-2 (IL-2) -330 T/G promoter polymorphism is involved in the acute rejection (AR) risk of kidney transplantation. However, results from published studies on the association between recipient IL-2-330 T/G polymorphism and AR risk are conflicting and inconclusive.

METHODS

We searched Medline, Embase, Web of Science, and Cochrane Central Register from their inceptions through January 2015 for relevant studies. Data concerning publication information, population characteristics, and transplant information were extracted. Odds ratios (ORs) were calculated for the association between IL-2-330 T/G polymorphism and AR risk.

RESULTS

This meta-analysis included 8 case-control studies with 1,405 cases of renal transplant recipients. The pooled estimate showed that IL-2-330 T/G polymorphism was not associated with AR risk: TT vs TG+GG: OR(fixed,) 0.93; 95% confidence interval [CI], 0.72-1.21; P = .60; GG vs TG+TT: OR(fixed), 1.15; 95% CI, 0.76-1.72; P = .51; TG vs TT+GG: OR(fixed), 1.01; 95% CI, 0.78-1.31; P = .91; T vs G: OR(fixed), 0.93; 95% CI, 0.77-1.13; P = .48. None of subgroup analyses yielded significant results in the association between IL-2-330 T/G polymorphism and AR risk. Meta-regression confirmed that there was no significant correlation between the preselected trial characteristics and our study results.

CONCLUSIONS

This meta-analysis suggests that IL-2-330 T/G polymorphism may not be associated with AR risk in renal transplant recipients.

[Evaluation and analysis of the tibial coronal alignment after total knee replacement with the extramedullary tibial cutting guided by the tibial tubercle and anterior tibial tendon in Chinese patients]

OBJECTIVE

To evaluate the efficiency of the tibial coronal alignment after total knee arthroplasty with the extramedullary cutting system guided by the tibial tubercle and anterior tibial tendon, and to discuss the potential risk factors for the postoperative malalignment.

METHODS

A retrospective study of 212 primary unilateral TKA surgeries (in 188 patients) in our hospital between June to December in 2014 had been analysed. All the cases were performed by one surgical group. An extramedullary tibial cutting guide system had been used, with a landmark of one third inner-medial tibial tubercle as a proximal anatomy reference, and anterior tibial tendon as a distal marker. The mechanical axis of lower extremity in full-length X-ray was measured before surgery, and the tibial prosthetic coronal alignment was checked two weeks postoperation, evaluating the accuracy of this extramedullary cutting system guided by our method.

RESULTS

Since good alignment was defined as an angle within 3 degrees of the perpendicular to the mechanical axis, the tibial component positions were acceptable in 191 knees (90.1%), five knees were in valgus postoperative, and sixteen knees were in varus. There were seventeen(8.7%) in 179 knees with a preoperative varus presented malalignment after surgery, and four in 12 preoperative valgus kneess howed malalignment also, no statistical difference was found by Chi-square test(χ(2)=2.778,P=0.096), which cannot define the relationship between the varus or valgus deformity preoperation and the malalignmentposition in tibial prosthesis after surgery. Twenty-two knees suffered a severe preoperative deformity as a varus or valgus angle larger than 20 degrees with absolute value of mechanical axis before surgery and tibial prosthetic coronal alignment were 21.95 °(20.00°,26.90°)and 1.85°(0.10°, 7.10°), showed a significant difference (Z=2.11,P=0.035) compared with the data [10.65°(0.50°,19.80°)in preoperative mechanical axis and 1.10°(0.00°,4.60°)in the tibial prosthetic coronal alignment]of 190 knees who presented a mild deformity before surgery(less than 20 degrees), the result indicated the severe preoperative deformity might be a potential mal-alignment risk factor within this cutting system in TKA surgery.

CONCLUSION

The tibial coronal alignment after total knee arthroplasty could achieve good results with extramedullary cutting guide, by using one third inner-medial tibial tubercle and anterior tibial tendon as a proximal and distal anatomy marker. Postoperative varus might occur in this system, and tibial prosthetic malalignment appeared more often in the patients who suffered a severe deformity before surgery.

Methods of applying the 1994 case definition of chronic fatigue syndrome - impact on classification and observed illness characteristics

BACKGROUND

Multiple case definitions are in use to identify chronic fatigue syndrome (CFS). Even when using the same definition, methods used to apply definitional criteria may affect results. The Centers for Disease Control and Prevention (CDC) conducted two population-based studies estimating CFS prevalence using the 1994 case definition; one relied on direct questions for criteria of fatigue, functional impairment and symptoms (1997 Wichita; Method 1), and the other used subscale score thresholds of standardized questionnaires for criteria (2004 Georgia; Method 2). Compared to previous reports the 2004 CFS prevalence estimate was higher, raising questions about whether changes in the method of operationalizing affected this and illness characteristics.

METHODS

The follow-up of the Georgia cohort allowed direct comparison of both methods of applying the 1994 case definition. Of 1961 participants (53 % of eligible) who completed the detailed telephone interview, 919 (47 %) were eligible for and 751 (81 %) underwent clinical evaluation including medical/psychiatric evaluations. Data from the 499 individuals with complete data and without exclusionary conditions was available for this analysis.

RESULTS

A total of 86 participants were classified as CFS by one or both methods; 44 cases identified by both methods, 15 only identified by Method 1, and 27 only identified by Method 2 (Kappa 0.63; 95 % confidence interval [CI]: 0.53, 0.73 and concordance 91.59 %). The CFS group identified by both methods were more fatigued, had worse functioning, and more symptoms than those identified by only one method. Moderate to severe depression was noted in only one individual who was classified as CFS by both methods. When comparing the CFS groups identified by only one method, those only identified by Method 2 were either similar to or more severely affected in fatigue, function, and symptoms than those only identified by Method 1.

CONCLUSIONS

The two methods demonstrated substantial concordance. While Method 2 classified more participants as CFS, there was no indication that they were less severely ill or more depressed. The classification differences do not fully explain the prevalence increase noted in the 2004 Georgia study. Use of standardized instruments for the major CFS domains provides advantages for disease stratification and comparing CFS patients to other illnesses.

Correlation analysis between an IL-6 genetic polymorphism and non-small cell lung cancer prognosis

Interleukin-6 (IL-6) is a multifunctional cytokine that is involved in tumor cell proliferation, apoptosis, and differentiation. The purpose of this study was to evaluate the impact of the single nucleotide polymorphism (SNP) -174G/C in IL-6 on the prognosis and pain tolerance of non-small cell lung cancer (NSCLC) patients. DNA was extracted from the peripheral blood of 434 patients with NSCLC, which was diagnosed by cytology or histology. Polymerase chain reaction-restriction fragment length polymorphism was used to detect the IL-6 -174G/C genotypes and their correlation with survival was analyzed. The IL-6 -174G/C genotypes were high IL-6 production type (G carriers - GG or GC genotypes) and low IL-6 production type (CC genotype). The correlation between the IL-6 SNP and pain level/analgesic use was also analyzed. Survival analysis showed that patients carrying the G allele (CG/GG) had a shorter survival time than patients with the CC genotype. The -174G/C SNP is in the promoter region of the IL-6 gene and may be associated with changes in gene transcription and serum cytokine levels. Presence of the IL-6 -174G/C SNP is significantly correlated with morphine equivalent daily dose. Patients with the CC genotype needed a higher opioid dose than patients with the GG or GC genotypes. In conclusion, we found that the IL-6 -174G/C SNP is closely related to survival, analgesic use and pain tolerance in NSCLC patients. However, it is necessary to further validate the results with a larger patient cohort and elucidate the mechanisms of this SNP.

Extracellular Tau Oligomers Produce An Immediate Impairment of LTP and Memory

Non-fibrillar soluble oligomeric forms of amyloid-β peptide (oAβ) and tau proteins are likely to play a major role in Alzheimer's disease (AD). The prevailing hypothesis on the disease etiopathogenesis is that oAβ initiates tau pathology that slowly spreads throughout the medial temporal cortex and neocortices independently of Aβ, eventually leading to memory loss. Here we show that a brief exposure to extracellular recombinant human tau oligomers (oTau), but not monomers, produces an impairment of long-term potentiation (LTP) and memory, independent of the presence of high oAβ levels. The impairment is immediate as it raises as soon as 20 min after exposure to the oligomers. These effects are reproduced either by oTau extracted from AD human specimens, or naturally produced in mice overexpressing human tau. Finally, we found that oTau could also act in combination with oAβ to produce these effects, as sub-toxic doses of the two peptides combined lead to LTP and memory impairment. These findings provide a novel view of the effects of tau and Aβ on memory loss, offering new therapeutic opportunities in the therapy of AD and other neurodegenerative diseases associated with Aβ and tau pathology.

Structural phase transition and spin reorientation of LaFeO3 films under epitaxial strain

Structural phase transition and spin reorientation of orthoferrites LaFeO₃ epitaxially grown along the pseudocubic (001) direction are investigated based on first-principles calculation.

The curative effects of LPN combined LCA in treating with middle and advanced renal cancer

OBJECTIVE

To discuss the curative effects of laparoscopy partial nephrectomy (LPN) combined with laparoscopy cryoablation (LCA) in treating renal cancer.

PATIENTS AND METHODS

A total of 58 patients that were diagnosed with phase III-IV renal cancer in the Hospital from February 2013 to October 2014 were enrolled in this study. After obtaining the approval of Ethics Committee of the Hospital as well as the informed consent of the patients and their relatives, the patients were randomly divide into two groups: control group consisted of 24 patients, who were treated with LPN + chemo radiotherapy and the observation group consisted of 34 patients, who were treated with LPN in combination of LCA + chemo radiotherapy.

RESULTS

The rate of successful operation was significantly higher in the observation group than in control group and the prevalence of per procedural complications in observation group was significantly lower than that of control group, and these differences had statistical significance (p < 0.05). Glomerular filtration rate (eGFR) after operation and 6-month follow-up in observation group was significantly higher than that in control group, and the level of serum creatinine (sCr) was significantly lower compared to the control group and the differences had statistical significance (p < 0.05). Follow-up survival rate of patients in the observation group was significantly higher than that of control group, recurrence rate and recurrence time of patients in the observation group was significantly lower than those of control group and the difference had statistical significance (p < 0.05).

CONCLUSIONS

LPN combined LCA therapy was quite effective in treating with middle and advanced renal cancer. Compared with pure LPN therapy, LPN combined LCA therapy could significantly improve the surgical effects, retain the functions of the renal unit and improve the patients' prognosis.

Colossal dielectric performance of pure barium titanate ceramics consolidated by spark plasma sintering

The pure BaTiO₃ nanoceramics have a high permittivity up to 6 × 10⁴ and a low dielectric loss. The polaron dipoles configured by oxygen vacancies and Ti³⁺ cations within grains could contribute to the colossal dielectric permittivity of the ceramics.

Downregulation of miR-320a/383-sponge-like long non-coding RNA NLC1-C (narcolepsy candidate-region 1 genes) is associated with male infertility and promotes testicular embryonal carcinoma cell proliferation

Long non-coding RNAs (lncRNAs), which are extensively transcribed from the genome, have been proposed to be key regulators of diverse biological processes. However, little is known about the role of lncRNAs in regulating spermatogenesis in human males. Here, using microarray technology, we show altered expression of lncRNAs in the testes of infertile men with maturation arrest (MA) or hypospermatogenesis (Hypo), with 757 and 2370 differentially down-regulated and 475 and 163 up-regulated lncRNAs in MA and Hypo, respectively. These findings were confirmed by quantitative real-time PCR (qRT-PCR) assays on select lncRNAs, including HOTTIP, imsrna320, imsrna292 and NLC1-C (narcolepsy candidate-region 1 genes). Interestingly, NLC1-C, also known as long intergenic non-protein-coding RNA162 (LINC00162), was down-regulated in the cytoplasm and accumulated in the nucleus of spermatogonia and primary spermatocytes in the testes of infertile men with mixed patterns of MA compared with normal control. The accumulation of NLC1-C in the nucleus repressed miR-320a and miR-383 transcript and promoted testicular embryonal carcinoma cell proliferation by binding to Nucleolin. Here, we define a novel mechanism by which lncRNAs modulate miRNA expression at the transcriptional level by binding to RNA-binding proteins to regulate human spermatogenesis.

[Expressing foreign genes by Newcastle disease virus for cancer therapy]

An interesting aspect of Newcastle disease virus (NDV) is the ability to selectively replicate in tumor cells. Recently, using reverse genetics technology to enhance the oncolytic properties and therapeutic potential of NDV for tumor therapy has become popular in immunocompetent carcinoma tumor models. Expressing foreign genes by recombinant NDV (rNDV-FG) has been shown to be more effective in cancer therapy in preclinical studies. This paper provides an overview of the current studies on the cytotoxic and anti-cancer effects of rNDV-FG via direct oncolysis and immune stimulation. Safety of rNDV-FG as a therapeutic agent for cancer immunotherapy and virotherapy is also discussed.

Relationship between genetic polymorphisms of DNA ligase 1 and non-small cell lung cancer susceptibility and radiosensitivity

The aim of this study was to examine the relationship between genetic polymorphisms in DNA ligase 1 (LIG1) and non-small cell lung cancer (NSCLC) susceptibility and radiosensitivity in a Chinese population. This was a case-control study that included 352 NSCLC patients and 448 healthy controls. Polymerase chain reaction-restriction fragment length polymorphism analysis was conducted to detect HaeIII polymorphisms in exon 6 of the LIG1 gene in this popula-tion. This information was used to observe the effects of radiation in pa-tients with different genotypes in order to determine the genotypes as-sociated with radiosensitivity. The CC genotype and C allele frequency were significantly higher in the NSCLC group than in the control group (P = 0.012 and P = 0.023, respectively). The relative risk of experienc-ing NSCLC was 2.55 [95% confidence interval (CI), 1.12-3.98] for CC homozygous patients and 0.87 (95%CI, 0.46-1.88) for AA homozygous patients. Analysis of LIG1 genetic polymorphisms and radiosensitiv-ity of NSCLC patients showed that AA homozygous patients were sig-nificantly more radiosensitive than the control group (AA vs AC, P = 0.014; AA vs CC, P < 0.001; AC vs CC, P = 0.023). Therefore, the LIG1 CC genotype was associated with susceptibility to NSCLC, and the AA genotype demonstrated increased radiosensitivity compared to the AC and CC genotypes.

Effects of maternal anxiety and depression during pregnancy in Chinese women on children's heart rate and blood pressure response to stress

Psychological disturbances, including anxiety and depression, are common during human pregnancy. Our objective was to determine whether these maternal disturbances influence cardiovascular responses of the offspring. The psychological status of 231 pregnant women was determined. Offspring (216) of these women were subsequently exposed to a video challenge stress when aged 7-9 years. Heart rate (HR) and blood pressure (BP) of the children were determined at rest, in response to video stress and during subsequent recovery. Children's resting and stress-induced increases in HR (bpm), systolic (SBP, mm Hg) and diastolic (DBP, mm Hg) BP were all greater in children whose mothers reported anxiety during pregnancy. Values (mean±s.d.) for resting HR, SBP and DBP were 75.15±5.87, 95.37±2.72 and 66.39±4.74 for children whose mothers reported no anxiety and an average of 81.62±6.71, 97.26±2.90 and 68.86±2.82 for children whose mothers reported anxiety at any level. Respective values for stress-induced increments in HR, SBP and DBP were 14.83.±2.14, 16.41±1.97 and 12.72±2.69 for children whose mothers reported no anxiety and 17.95±3.46, 18.74±2.46 and 14.86±2.02 for children whose mothers reported any level of anxiety. Effects of maternal depression were less consistent. The effects of maternal anxiety remained in multivariate analyses, which also included children's birth weight. The results indicate a long-term influence of maternal psychological status during pregnancy on the cardiovascular responses to stress among offspring. These effects may contribute to prenatal influences on subsequent health of the offspring.

Use of multisequence 3.0-T MRI to detect severe traumatic brain injury and predict the outcome

OBJECTIVE

The aim of this study was to evaluate multisequence 3.0-T MRI in the detection of severe traumatic brain injury (sTBI) and in predicting the outcome.

METHODS

32 patients with sTBI were prospectively enrolled, and multisequence 3.0-T MRI was performed 4-8 weeks post injury. Quantitative data were recorded on each sequence. The ability to display the parenchymal lesions was compared with that of 64-slice spiral CT. The clinical and radiological results were correlated with the Glasgow Outcome Scale Extended scores 6 months after injury.

RESULTS

3.0-T MRI could display more lesions than CT, especially when the lesion was deeply located. The lesion volumes and diffuse axonal injury (DAI) scores were different between good and poor outcome groups on fluid attenuated inversion recovery (p < 0.05). The apparent diffusion coefficient (ADC) values of the splenium of the corpus callosum and brain stem were also different (p < 0.05). Patients with unfavourable outcome showed a significantly higher volume of haemorrhage on susceptibility-weighted imaging than those with favourable outcomes and had haemorrhages generally located more deeply. Logistic regression analysis revealed that the location of haemorrhage and the ADC values of the splenium of the corpus callosum were independent risk factors for poor outcome, with an overall predictive accuracy of 91.4%.

CONCLUSION

The joint use of conventional and advanced sequences of 3.0-T MRI can comprehensively detect the pathological changes occurring after sTBI. Haemorrhagic and non-haemorrhagic DAIs in deep structures strongly suggest poor outcome.

ADVANCES IN KNOWLEDGE

This article improves the understanding of advanced MRI sequences in the detection of patients with sTBI and prediction of prognosis.

HPV 16 infection up-regulates Piwil2, which affects cell proliferation and invasion in cervical cancer by regulating MMP-9 via the MAPK pathway

PURPOSE OF INVESTIGATION

The present study aimed to investigate the effect of Piwil2 on proliferation and invasion of cervical cancer cells.

MATERIALS AND METHODS

Thirty-two HPV-positive or negative cervical cancer tissues and corresponding normal adjacent cervical tissues were obtained from General Hospital of Lanzhou Military Region. Piwil2 expression in these tissue samples, as well as two cervical cell lines were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemical. A specific short hairpin RNA (shRNA) was used to knockdown the Piwil2 gene in SiHa cells. CCK-8 assay and flow cytometry (FCM) was used to evaluate cell proliferation. Cell invasion was detected by transwell chambers assays. Immunoblotting was used to assess the effect on relevant proteins.

RESULT

In the early stage (I A1-I B1) of curvival, 84.4% (27/32) tumor tissues have a more predominant expression of Piwil2 than the normal adjacent samples. Piwil2 overexpression was correlated with HPV16 infection (p < 0.05). Knockdown of Piwil2 gene in SiHa cells inhibited cell growth and invasion, and downregulated matrix metalloproteinase-9 (MMP-9) compared to scrambled shRNA transfected cells. Further analysis revealed that downregulation of Piwil2 gene induced inhibition of the MAPK signaling pathway activity.

CONCLUSION

Piwil2, which stimulated by HPV16 infection, plays an important role in regulating proliferation and invasion of cervical cells by regulating MMP-9 expression via alternation of the MAPK signaling pathway.

Prevalence of small-scale jets from the networks of the solar transition region and chromosphere

As the interface between the Sun's photosphere and corona, the chromosphere and transition region play a key role in the formation and acceleration of the solar wind. Observations from the Interface Region Imaging Spectrograph reveal the prevalence of intermittent small-scale jets with speeds of 80 to 250 kilometers per second from the narrow bright network lanes of this interface region. These jets have lifetimes of 20 to 80 seconds and widths of ≤300 kilometers. They originate from small-scale bright regions, often preceded by footpoint brightenings and accompanied by transverse waves with amplitudes of ~20 kilometers per second. Many jets reach temperatures of at least ~10(5) kelvin and constitute an important element of the transition region structures. They are likely an intermittent but persistent source of mass and energy for the solar wind.

Evidence of nonthermal particles in coronal loops heated impulsively by nanoflares

The physical processes causing energy exchange between the Sun's hot corona and its cool lower atmosphere remain poorly understood. The chromosphere and transition region (TR) form an interface region between the surface and the corona that is highly sensitive to the coronal heating mechanism. High-resolution observations with the Interface Region Imaging Spectrograph (IRIS) reveal rapid variability (~20 to 60 seconds) of intensity and velocity on small spatial scales (≲500 kilometers) at the footpoints of hot and dynamic coronal loops. The observations are consistent with numerical simulations of heating by beams of nonthermal electrons, which are generated in small impulsive (≲30 seconds) heating events called "coronal nanoflares." The accelerated electrons deposit a sizable fraction of their energy (≲10(25) erg) in the chromosphere and TR. Our analysis provides tight constraints on the properties of such electron beams and new diagnostics for their presence in the nonflaring corona.

The unresolved fine structure resolved: IRIS observations of the solar transition region

The heating of the outer solar atmospheric layers, i.e., the transition region and corona, to high temperatures is a long-standing problem in solar (and stellar) physics. Solutions have been hampered by an incomplete understanding of the magnetically controlled structure of these regions. The high spatial and temporal resolution observations with the Interface Region Imaging Spectrograph (IRIS) at the solar limb reveal a plethora of short, low-lying loops or loop segments at transition-region temperatures that vary rapidly, on the time scales of minutes. We argue that the existence of these loops solves a long-standing observational mystery. At the same time, based on comparison with numerical models, this detection sheds light on a critical piece of the coronal heating puzzle.