Gemcitabine combined with cisplatin vs. taxane, cisplatin, and fluorouracil in the treatment of locally advanced nasopharyngeal carcinoma: a retrospective case-control study

OBJECTIVE

Reports of the efficacy of induction chemotherapy (IC) combined with concurrent chemoradiotherapy (CCRT) on locoregionally advanced nasopharyngeal carcinoma (NPC) are scarce. This study aimed to compare the clinical outcomes of the GP (gemcitabine plus cisplatin) regimen and the TPF (taxane, cisplatin and 5-FU) regimen combined with CCRT in patients with NPC.

PATIENTS AND METHODS

This study retrospectively analyzed 827 patients with advanced NPC who received IC combined with CCRT in People's Hospital of Rizhao, China from January 2006 to June 2012. The propensity score method was used to reduce the effects of the observed confounding between the GP and TPF groups. Study end points were disease-free survival (DFS) and overall survival (OS). In total, 694 patients received GP or TPF as the IC treatment program. Propensity score matching identified 166 patients in each cohort.

RESULTS

The 5-year OS and DFS rates of the entire cohort were 83.5% and 80.9%, respectively. GP was associated with a significantly improved 5 year OS (87.4% vs. 79.2%, p< 0.001), and DFS (86.2% vs. 78.5%, p< 0.001) rates compared with the TPF group. In the PSM (propensity score-matching) cohort, the GP group showed a significantly better OS (HR, 1.842, 95% CI:1.627-2.588; p= 0.011), and DFS (HR, 1.904, 95% CI: 1.742-2.737; p= 0.004) compared with the TPF group in multivariable analyses. The prevalence of acute adverse events of neutropenia and leukopenia were higher in severe (grade 3-4) adverse blood events in the TPF group (p<0.05). Thrombocytopenia had more adverse reactions in the GP group (p<0.05). The main non-hemotoxicities were nausea and vomiting, while the TPF group was slightly higher (p=0.031).

CONCLUSIONS

The clinical efficacy of the GP regimen combined with CCRT for the treatment of locoregionally advanced NPC may be better than that of the TPF regimen.

Beneficial effects of endophytic Pantoea ananatis with ability to promote rice growth under saline stress

AIMS

Soil salinization severely inhibits plant growth, leading to a low crop yield. The aim of the current study was to isolate endophytic bacteria with the ability to promote rice growth under saline conditions.

METHODS AND RESULTS

We isolated eight salt-tolerant endophytic bacteria from rice roots. An isolated strain D1 was selected due to its ability to stimulate rice seed germination in the presence of NaCl, which was identified as Pantoea ananatis D1. It exhibited multiple plant growth-promoting traits including phosphate solubilization, production of indole-3-acetic acid, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and siderophore. Inoculation of P. ananatis D1 obviously enhanced the rice root and shoot growth under normal and saline conditions. It also significantly increased the contents of chlorophyll, total soluble protein, and proline in salt-stressed rice seedlings. Moreover P. ananatis D1 could ameliorate the oxidative stress in rice induced by NaCl and Na₂ CO₃ treatment. The malondialdehyde content and various antioxidant enzyme activities were decreased by P. ananatis D1 inoculation in salt-affected rice. In addition, P. ananatis D1 showed a positive potential for limiting the Na⁺ accumulation and enhancing the K⁺ uptake, leading to an increase of 1·2-1·7 fold in K⁺ /Na⁺ ratio under saline environment.

CONCLUSIONS

Pantoea ananatis D1 has the ability to improve the salt tolerance of rice seedlings.

SIGNIFICANCE AND IMPACT OF THE STUDY

The application of plant growth-promoting bacteria (PGPB) is an eco-friendly strategy to improve plant tolerance towards abiotic stresses. We demonstrated that P. ananatis D1 could be used as an effective halotolerant PGPB to enhance rice growth in different salt-affected soils.

[Research study on nucleic acid testing of hemostatic stickers used and the surface of the recipients' hands after the inoculation of inactivated SARS-CoV-2 vaccine]

Among the staff of Beijing Chao-Yang Hospital, Capital Medical University, who received the inactivated SARS-CoV-2 vaccine on January 30 in 2021, 28 recipients were selected for this research. Samples for nucleic acid tests were collected from the surface of the recipients' both hands before and after vaccination. The hemostatic stickers used after the inoculation were also collected for nucleic acid tests. The nucleic acid tests of the samples collected from the surface of both hands of the 28 recipients before vaccination were all negative. After vaccination, the nucleic acid tests of the samples collected from the surface of both hands of recipients were positive in 3 cases, and suspicious in 8 cases, with a positive rate of 10.7%. A total of 25 hemostatic stickers used were collected, 24 of them had positive nucleic acid tests, and the rest one had suspicious nucleic acid test result, with a positive rate of 96%. The hemostatic stickers used after the inoculation have the risk of nucleic acid contamination.

Targeting EZH2 by microRNA-449a inhibits osteosarcoma cell proliferation, invasion and migration via regulation of PI3K/AKT signaling pathway and epithelial-mesenchymal transition

OBJECTIVE

Osteosarcoma (OS) is one common bone malignant tumor prevailing in young adults and children. It is increasingly recognized microRNA 449a (miR 449a) as an anti-tumor factor in various tumours. However, little is known about the biological significance of miR 449a in OS. The intent of our study was to seek the prognostic values of miR-449a in OS.

PATIENTS AND METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to examine the level of miR-449a expression in 48 pairs of OS tissues and para-cancerous specimens, and the relationship between miR-449a level and clinical features of OS patient prognosis was analyzed. Moreover, we measured the miR-449a expression levels in OS cells. Transwell assay was further performed to investigate whether miR-449a influenced MG63 cell migration and invasion, which was important for malignant metastases.

RESULTS

Quantitative real-time polymerase chain reaction (qRT-PCR) analysis demonstrated a notable decrease of miR-449a expressions in OS. The declined miR-449a expression was relevant with the poor prognosis and malignant clinicopathologic characteristics of OS patients. Thereafter, the functional assay was performed to determine the role of miR-449a in OS progression. Results of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assays and transwell assays indicated that miR-449a overexpression significantly repressed OS cell proliferation, invasion, and migration. Furthermore, luciferase reporter assay showed that enhancer of zeste homolog 2 (EZH2) was a downstream target of miR-449a in OS cells. Additionally, Western blot analysis demonstrated that miR-449a exerted anti-OS functions via the regulation of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway and epithelial-mesenchymal transition. We also indicated that miR-449a restoration could inhibit in vivo tumor growth.

CONCLUSIONS

These results manifested that miR-449a may thus be used as a therapeutic target in OS treatments.

Multiscale measurements with adjustable x-ray spot size for in situ imaging and diffraction

A large field of view is normally desired for synchrotron x-ray imaging, while a small x-ray spot size is required for x-ray diffraction. A multiscale measurement system with an adjustable x-ray spot size is developed to accommodate different spot size requirements for in situ phase-contrast imaging and diffraction. The centers of a diffraction scintillator with a through-hole and an imaging scintillator are collinear with the x-ray beam. With the proof-of-principle experiments on a magnesium alloy under uniaxial tension, we demonstrate the feasibility of the multiscale measurement system for full azimuthal range diffraction measurements with improved resolution and large field of view strain field measurements via x-ray digital image correlation.

[Expert consensus on the treatment of oral and maxillofacial space infections]

Oral and maxillofacial space infections (OMSI) are common diseases of the facial region involving fascial spaces. Recently, OMSI shows trends of multi drug-resistance, severe symptoms, and increased mortality. OMSI treatment principles need to be updated to improve the cure rate. Based on the clinical experiences of Chinese experts and with the incorporation of international counterparts' expertise, the principles of preoperative checklist, interpretation of examination results, empirical medication principles, surgical treatment principles, postoperative drainage principles, prevention strategies of wisdom teeth pericoronitis-related OMSI, blood glucose management, physiotherapy principles, Ludwig's angina treatment and perioperative care were systematically summarized and an expert consensus on the diagnosis and treatment of OMSI was reached. The consensus aims to provide criteria for the diagnosis and treatment of OMSI in China so as to improve the level of OMSI treatment.

[Prevalence and related factors of dyslipidemia in patients with 21-hydroxylase deficiency]

Objective: To analyze the prevalence and the related factors of dyslipidemia in 21-hydroxylase deficiency (21-OHD) patients. Methods: A total of 205 patients with 21-OHD were recruited in Peking Union Medical College Hospital from January 2016 to January 2018. The basic information, glucocorticoid replacement therapy, and laboratory examination results of patients were obtained from medical records. The genotypes of CYP21A2 were identified by Sanger sequencing and multiplex ligation dependent probe amplification. The prevalence of dyslipidemia among 21-OHD patients, basic information and related hormone levels of 21-OHD patients with different status of blood lipid were described. Logistic regression model was used to analyze the related factors of dyslipidemia in 21-OHD patients. Results: The age of subjects was 17.0 (8.3, 25.0) years old, including 51 males (24.9%). According to CYP21A2 genotypes, there were 16 cases in Null group, 26 cases in Group A, 105 cases in group B, 27 cases in group C, and 31 cases in group D. The incidence of dyslipidemia was 29.3% (60/205), among which 37.3% (19/51) in male and 26.6% (41/154) in female patients, respectively. The M (Q₁, Q₃) of total cortisol level (nmol/L) and body mass index (kg/m²) of male 21-OHD patients with dyslipidemia were 0.17 (0.06, 0.35) and 25.76 (17.01, 30.45), respectively, which were higher than those with ortholiposis [0.04 (0.02, 0.21) and 18.83 (16.53, 23.88)] (all P<0.05). The M (Q₁, Q₃) of progesterone level (nmol/L), body mass index (kg/m²) and age (years) of female 21-OHD patients with dyslipidemia were 74.40 (50.97, 98.52), 23.09 (21.78, 27.78) and 23.00 (16.50, 28.00), respectively, which were higher than those with ortholiposis [52.81 (33.41, 68.85), 21.55 (18.63, 25.71) and 18.00 (9.50, 25.00)] (all P<0.05). The risk of dyslipidemia increased by 5.0% [OR (95%CI): 1.05 (1.01, 1.09)] for every 1 nmol/L increase of progesterone. Conclusion: The incidence of dyslipidemia is high in 21-OHD patients, and progesterone level is positively correlated with dyslipidemia.

Persistent negative symptoms in youth at clinical high risk for psychosis: A longitudinal study

BACKGROUND

Severity of negative symptoms has been associated with poor functioning, cognitive deficits, and defeatist beliefs in schizophrenia patients. However, one area that remains understudied is persistent negative symptoms (PNS). Negative symptoms, including PNS, have been observed in those at clinical high-risk (CHR) for psychosis. The aim of this study was to determine if PNS were associated with functioning, neurocognition, and defeatist beliefs in a CHR sample.

METHOD

CHR participants (n = 764) were recruited for the North American Prodrome Longitudinal Study. Negative symptoms were rated on the Scale of Psychosis-risk Symptoms. Generalized linear mixed models for repeated measures were used to examine changes over time between and within groups (PNS vs non-PNS).

RESULTS

The PNS group (n = 67) had significant deficits in functioning at baseline, 6, 12, 18, and 24-months compared to the non-PNS group (n = 673). Functioning improved over time in the non-PNS group, while functioning in the PNS group remained relatively stable and poor over a two-year period. A consistent trend emerged demonstrating higher defeatist beliefs in the PNS group; however, this result was lost when controlling for persistent depressive symptoms. There were no significant differences between the groups on neurocognition, social cognition, and transition to psychosis.

CONCLUSIONS

PNS exist in youth at CHR for psychosis, resulting in significant and persistent functional impairment, which remains when controlling for persistent depressive symptoms. PNS remain even in CHR youth who do not transition to psychosis. Thus, PNS may represent an unmet therapeutic need in CHR populations for which there are currently no effective treatments.

Pattern-recognition receptors in duck (Anas platyrhynchos): identification, expression and function analysis of toll-like receptor 3

1. Innate immunity provides the first line of defence against pathogenic organisms through a myriad of germline encoded receptors called pattern-recognition receptors (PRRs). Toll-like receptor (TLR) 3, as an important member of PRRs, is indispensable for host defence against viral infection by recognising virus-derived RNAs. However, little is known about the structure and function of TLR3 in ducks (Anas platyrhynchos), a natural host for the avian influenza virus.2. This study cloned the full-length cDNA of duck TLR3 using reverse transcription polymerase chain reaction (RT-PCR) with rapid amplification of cDNA ends (RACE). The cDNA sequence of duck TLR3 was 4046 bp in length and encoded 895 amino acids. Multiple sequence alignment showed that duck TLR3 shared high similarity with that from other vertebrates.3. Quantitative real-time PCR (qRT-PCR) analysis suggested that TLR3 mRNA was constitutively expressed in all tissues tested, having higher levels in the kidney, liver, breast muscle, ovary and heart. After stimulation with viral- or bacterial-mimics, including LPS, poly(I:C), pam3CSK4, FLS-1, FLA-ST and R848, the TLR3 transcript was significantly upregulated. Meanwhile, overexpression of duck TLR3 significantly promoted the transcription of IFN-β, IRF7, TRIF, Mx, STAT1 and STAT2 mRNA after stimulation with poly(I:C).4. These results suggested that TLR3 play an important role in resistance against viral and bacterial infections in ducks.

Epicardial adipose tissue is associated with the formation of left ventricular aneurysm after myocardial infarction

Background

Left ventricular aneurysm (LVA), a serious complication of transmural myocardial infarction, is generally related to poor cardiovascular outcomes. The formation of LVA is essentially an inflammatory remodeling process regulated by multiple systemic and local factors. Epicardial adipose tissue (EAT), a depot of visceral adipose tissue directly overlying the myocardium, is increasingly recognized as an important immune organ by secreting a variety of bioactive adipocytokines. However, the relation of EAT to the development of LVA is still unclear.

Purpose

In this study, we sought to investigate the association between EAT volume and the formation of LVA in subjects with previous myocardial infarction (MI).

Methods

A total of 55 subjects with previous MI and the presence of LVA, and age- and sex-matched 50 subjects with previous MI but without LVA were enrolled between October 2011 and June 2019. EAT was quantified and the presence of LVA was ascertained by cardiac magnetic resonance (CMR). EAT volume was indexed to body surface area.

Results

In the overall population, EAT volume index was correlated positively to log-transformed N-terminal pro-brain natriuretic peptide (NT-proBNP) levels (Pearson's r=0.332, P=0.002), and inversely to left ventricular ejection fraction (LVEF; Pearson's r=−0.240, P=0.031). The indexed EAT volume was significantly higher in subjects with than without LVA (41.10±11.73 vs. 33.25/11.70 mL/m2, P=0.003). In subjects with LVA, EAT volume index was further increased in those at older age (43.59±13.09 mL/m2 vs. 37.29±8.26 mL/m2, P=0.029) or with type 2 diabetes (43.38±12.32 mL/m2 vs. 35.20±7.67 mL/m2, P=0.013). After adjusting for sex, age and the presence of diabetes in the multivariate analysis, tertiles of EAT volume index remained significantly associated with the presence of LVA (P for trend=0. 003). Strikingly, compared to the lowest tertile (≤30.80 mL/m2), the intermediate (30.80–44.13 mL/m2) and highest (&gt;44.13 mL/m2) tertiles of EAT volume index corresponded to 4.869– (95% CI 1.792–14.155, P=0.003) and 4.876– (95% CI, 1.787–14.206, P=0.003) increased risk for LVA.

Conclusion

Our study suggests that EAT volume is independently associated with the formation of LVA and reduced cardiac function after myocardial infarction.

EAT in patients with or without LVA

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Natural Science Foundation of China

Chromogranin B is associated with impaired coronary collateralization and heart failure in patients with stable angina and chronic total occlusion

Background

Chromogranin B (CgB) is a member of granin family that can be cleaved into a number of bioactive peptides. Previous studies showed that CgB is produced in cardiomyocytes and is increased in heart failure animals and patients in proportion to disease severity. Chronic total occlusion (CTO) of coronary artery leads to sustained myocardial ischemia which predisposes to adverse cardiovascular outcomes including heart failure.

Purpose

In this study, we sought to investigate the association between CgB and coronary collateralization formation and heart failure in patients with stable angina and CTO.

Methods

A total of 720 subjects with stable angina and CTO of at least one major coronary artery were enrolled in this study. CgB was assayed using an ELISA kit and the degree of coronary collaterals supplying the distal aspect of a total occlusion from the contralateral vessel was graded according to Rentrop classification.

Results

These was a stepwise decrease in levels of CgB with increasing Rentrop grades of coronary collateralization (P=0.001). Compared with the good collateralization (Rentrop grade 2–3) group, CgB was significantly higher in subjects with poor coronary collateralization (Rentrop grade 0–1; 1222.95 [IQR 506.24–2710.24] pg/mL vs. 776.17 [IQR 276.24–2209.39] pg/mL, P&lt;0.001). Consistent results were found across subgroups of age, sex and the presence of diagnosed diabetes. In subjects with poor collateralization, CgB was positively correlated to N-terminal–pro-brain natriuretic peptide (NT-proBNP) levels (both log-transformed; Pearson's r=0.280, P=0.005). This correlation was markedly enhanced (Pearson's r=0.501, P&lt;0.001) in the poorly-collateralized heart failure subgroup with left-ventricular ejection fraction (LVEF) &lt;50%. Consistently, an inverse correlation was present between log-transformed CgB and LVEF (Pearson's r=−0.528, P&lt;0.001) in the same subgroup. After adjusting for conventional confounding factors and LVEF, CgB remained significantly associated with impaired coronary collateralization (odds ratio: 1.314 [95% CI 1.097–1.590], P=0.004). Inclusion of CgB led to a better diagnostic accuracy as confirmed by net reclassification improvement (NRI) of 17.70% (95% CI 8.08–27.32%, P&lt;0.001) and integrated discrimination improvement (IDI) of 1.98% (95% CI 0.63–3.34%, P=0.004).

Conclusions

CgB is an independent predictor of poor coronary collateralization and is related to worse heart function in patients with stable angina and CTO.

Figure 1

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Natural Science Foundation of China

Identification and application of the Pigm-1 gene in rice disease resistance breeding

Rice blast, caused by Magnaporthe oryzae, is one of the most destructive diseases of rice worldwide. The identification and utilization of resistance genes are crucial and significant for breeding resistant rice cultivars. We identified a resistance gene from Shuangkang77009, which is highly resistant to the rice blast isolate Guy11 using map-based cloning. We performed bulked segregant analysis combined with specific length amplified fragment sequencing. We also performed association analysis, candidate gene prediction and cDNA sequencing to identify the candidate gene. The resistance gene is located on chromosome 6, and we ultimately mapped the resistance locus to a 92-kb region. The resistance gene in Shuangkang77009 was allelic to PigmR, hereafter referred to as Pigm-1. The Pigm-1 protein had one amino acid change: serine (Ser) residue 860 was replaced by tyrosine (Tyr) in Pigm-1 compared with the previously identified Pigm protein, which significantly changed the structure of the Pigm-1 protein based on 3-D structure simulation. In addition, using the developed molecular marker linked to the Pigm-1 gene and molecular marker-assisted selection technology, we introduced the Pigm-1 gene into Minghui86, a widely used and excellent restorer. We generated 11 stable homozygous rice lines with desirable agronomic traits and strong resistance to rice blast. In conclusion, Pigm-1, a natural allelic variant of PigmR, was responsible for blast resistance in Shuangkang77009 rice. The molecular marker-assisted breeding strategy for Pigm-1 was highly efficient.

eV-Scale Sterile Neutrino Search Using Eight Years of Atmospheric Muon Neutrino Data from the IceCube Neutrino Observatory

The results of a 3+1 sterile neutrino search using eight years of data from the IceCube Neutrino Observatory are presented. A total of 305 735 muon neutrino events are analyzed in reconstructed energy-zenith space to test for signatures of a matter-enhanced oscillation that would occur given a sterile neutrino state with a mass-squared differences between 0.01 and 100  eV^{2}. The best-fit point is found to be at sin^{2}(2θ_{24})=0.10 and Δm_{41}^{2}=4.5  eV^{2}, which is consistent with the no sterile neutrino hypothesis with a p value of 8.0%.

[Establishment of Mathematical Models for Skeletal Age Determination of Extremitas Sternalis of Clavicle in Shanxi Adolescents]

Objective To develop mathematical models for skeletal age determination with multiple statistic method based on the correlation between age and the growth of the epiphysis of extremitas sternalis of clavicle in Shanxi adolescents. Methods The 562 Shanxi sternoclavicular joint samples （454 cases of modelling, 108 cases of external verification） were scanned by the thin-section computed tomography. After volume rendering was obtained, indicators such as area of epiphysis, area of metaphysis, longest diameter of epiphysis and longest diameter of metaphysis of both extremitas sternalis of clavicle were collected. Indicators such as the ratio of area of epiphysis to area of metaphysis, and the ratio of longest diameter of epiphysis to longest diameter of metaphysis of both sides were calculated. Then multiple linear regression and random forest discriminant models were used to build mathematical models for age determination of adolescents. Results The obtained indicators exhibited a strong correlation with age （r>0.85）. The multiple linear regression model for males and females （all 4 indicators entering the model） based on the ratio of longest diameter of epiphysis to longest diameter of metaphysis and the ratio of area of epiphysis to area of metaphysis had an internal validation accuracy rate （±1.0 year） of over 92% and 108 cases had an external validation accuracy rate of over 70% （±1.0 year）. The out of bag error rates of random forest discriminant models were less than 2% for people over 18.0 years old （≥18.0 years old） and under 18.0 years old. The external validation accuracy rates of the 108 cases were over 80%. Conclusion The regression and discriminant models established in this study have certain reliability and accuracy and can be used in age determination of Shanxi adolescents.

Relationship between the MAPK/ERK pathway and neurocyte apoptosis after cerebral infarction in rats

OBJECTIVE

The aim of this study was to explore the relationship between the mitogen-activated protein kinase (MAPK)/extracellular regulated protein kinase (ERK) pathway and neurocyte apoptosis after cerebral infarction in rats.

MATERIALS AND METHODS

Neural stem cells were isolated from rats by establishing the cerebral infarction model and sham model. Isolated cells were cultured in complete culture medium in vitro. Real-time quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) was used to detect the messenger ribonucleic acid (mRNA) expression of ERK1 and ERK2 in the MARK pathway. Western blotting was applied to examine the activation of the MAPK/ERK pathway and neuron-specific markers. The expression of neuron-specific enolase (NSE) was detected via immunofluorescence. Cell activity and apoptosis were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry, respectively.

RESULTS

The mRNA expressions of ERK1 and ERK2 in neural stem cells increased in a time-dependent manner after cerebral infarction in rats. The expressions of ERK1, ERK2, cyclin D1, Nestin, NSE and glial fibrillary acidic-protein (GFAP) in neural stem cells were significantly decreased after being treated with SCH772984. Cell activity, proliferation and differentiation were markedly inhibited. However, cleaved-caspase 3 protein and apoptosis rate were remarkably increased.

CONCLUSIONS

The MAPK/ERK pathway seriously affects neurocyte apoptosis after cerebral infarction in rats. When the MAPK/ERK pathway is inhibited, neurocyte apoptosis is remarkably increased after cerebral infarction in rats.

Characteristics of the Diffuse Astrophysical Electron and Tau Neutrino Flux with Six Years of IceCube High Energy Cascade Data

We report on the first measurement of the astrophysical neutrino flux using particle showers (cascades) in IceCube data from 2010-2015. Assuming standard oscillations, the astrophysical neutrinos in this dedicated cascade sample are dominated (∼90%) by electron and tau flavors. The flux, observed in the sensitive energy range from 16 TeV to 2.6 PeV, is consistent with a single power-law model as expected from Fermi-type acceleration of high energy particles at astrophysical sources. We find the flux spectral index to be γ=2.53±0.07 and a flux normalization for each neutrino flavor of ϕ_{astro}=1.66_{-0.27}^{+0.25} at E_{0}=100  TeV, in agreement with IceCube's complementary muon neutrino results and with all-neutrino flavor fit results. In the measured energy range we reject spectral indices γ≤2.28 at ≥3σ significance level. Because of high neutrino energy resolution and low atmospheric neutrino backgrounds, this analysis provides the most detailed characterization of the neutrino flux at energies below ∼100  TeV compared to previous IceCube results. Results from fits assuming more complex neutrino flux models suggest a flux softening at high energies and a flux hardening at low energies (p value ≥0.06). The sizable and smooth flux measured below ∼100  TeV remains a puzzle. In order to not violate the isotropic diffuse gamma-ray background as measured by the Fermi Large Area Telescope, it suggests the existence of astrophysical neutrino sources characterized by dense environments which are opaque to gamma rays.