The origin of different bending stiffness between double-stranded RNA and DNA revealed by magnetic tweezers and simulations.

The subtle differences in the chemical structures of double-stranded (ds) RNA and DNA lead to significant variations in their biological roles and medical implications, largely due to their distinct biophysical properties, such as bending stiffness. Although it is well known that A-form dsRNA is stiffer than B-form dsDNA under physiological salt conditions, the underlying cause of this difference remains unclear. In this study, we employ high-precision magnetic-tweezer experiments along with molecular dynamics simulations and reveal that the relative bending stiffness between dsRNA and dsDNA is primarily determined by the structure- and salt-concentration-dependent ion distribution around their helical structures. At near-physiological salt conditions, dsRNA shows a sparser ion distribution surrounding its phosphate groups compared to dsDNA, causing its greater stiffness. However, at very high monovalent salt concentrations, phosphate groups in both dsRNA and dsDNA become fully neutralized by excess ions, resulting in a similar intrinsic bending persistence length of approximately 39 nm. This similarity in intrinsic bending stiffness of dsRNA and dsDNA is coupled to the analogous fluctuations in their total groove widths and further coupled to the similar fluctuation of base-pair inclination, despite their distinct A-form and B-form helical structures.

Universality in RNA and DNA deformations induced by salt, temperature change, stretching force, and protein binding.

Nucleic acid deformations play important roles in many biological processes. The physical understanding of nucleic acid deformation by environmental stimuli is limited due to the challenge in the precise measurement of RNA and DNA deformations and the complexity of interactions in RNA and DNA. Magnetic tweezers experiments provide an excellent opportunity to precisely measure DNA and RNA twist changes induced by environmental stimuli. In this work, we applied magnetic tweezers to measure double-stranded RNA twist changes induced by salt and temperature changes. We observed RNA unwinds when lowering salt concentration, or increasing temperature. Our molecular dynamics simulations revealed the mechanism: lowering salt concentration or increasing temperature enlarges RNA major groove width, which causes twist decrease through twist-groove coupling. Combining these results with previous results, we found some universality in RNA and DNA deformations induced by three different stimuli: salt change, temperature, and stretching force. For RNA, these stimuli first modify the major groove width, which is transduced into twist change through twist-groove coupling. For DNA, these stimuli first modify diameter, which is transduced into twist change through twist-diameter coupling. Twist-groove coupling and twist-diameter coupling appear to be utilized by protein binding to reduce DNA and RNA deformation energy cost upon protein binding.

Kidney Function Measures and Mortality: A Mendelian Randomization Study.

RATIONALE & OBJECTIVE: Individuals with a low estimated glomerular filtration rate (eGFR) are at a high risk of death. However, the causes underpinning this association are largely uncertain. This study aimed to assess the causal relationship of low eGFR with all-cause and cause-specific mortality. STUDY DESIGN: Retrospective cohort study incorporating Mendelian randomization (MR). SETTING & PARTICIPANTS: Individual-level data from 436,214 White participants (54.3% female; aged 56.8±8.0 years) included in the UK Biobank. EXPOSURES: eGFR estimated using cystatin C (eGFRcyst). OUTCOMES: The outcomes of interest included all-cause mortality, cardiovascular mortality, cancer mortality, infection mortality, and other-cause mortality. ANALYTICAL APPROACH: Cox proportional hazards analysis for the conventional observational analyses; linear and nonlinear MR analyses implemented using genetic allele scores as instrumental variables representing kidney function to estimate the effect of kidney function on the survival outcomes. RESULTS: During a median follow-up of 12.1 years, there were 30,489 deaths, 6,098 of which were attributed to cardiovascular events, 15,538 to cancer, 1,516 to infection, and 7,227 to other events. In the conventional observational analysis, eGFRcyst exhibited a nonlinear association with all the outcomes. MR analysis suggested that a genetically predicted lower eGFRcyst was linearly associated with a higher rate of cardiovascular mortality (HR, 1.43; 95% CI, 1.18-1.75) across the entire measurement range (every 10-mL/min/1.73m2 decrement). Nonetheless, no causal associations between eGFRcyst and all-cause mortality (HR, 1.07; 95% CI, 0.98-1.17) or any types of noncardiovascular mortality were detected. LIMITATIONS: Potential misclassification of the actual cause of death, a nonrepresentative sample, and potential error in the interpretation of the magnitude of associations generated in MR analyses. CONCLUSIONS: These findings suggest a potential causal association between low eGFR and cardiovascular mortality in the general population, but no causal relationship with all-cause mortality or noncardiovascular mortality was observed. Further studies in other populations are warranted to confirm these findings. PLAIN-LANGUAGE SUMMARY: This study investigated the existence of a causal relationship between lower kidney function and death of different causes. Using data from 436,214 people in the United Kingdom, we applied conventional statistical analyses and those incorporating genetic data to implement Mendelian randomization, an approach that estimates causal associations. The observational analysis showed a nonlinear association between kidney function and various types of mortality outcomes. However, Mendelian randomization analysis suggested a linear increase in the risk of cardiovascular mortality with lower kidney function, but no causal link between the level of kidney function and all-cause or noncardiovascular mortality was identified. Managing kidney health may help reduce cardiovascular mortality, but caution is needed in interpreting the magnitudes of these results. Further validation in other populations and in those with advanced kidney failure is needed.

Long-Term Survival and Recurrence Patterns in Locally Advanced Esophageal Squamous Cell Carcinoma Patients with Pathologic Complete Response After Neoadjuvant Chemotherapy Followed by Surgery.

BACKGROUND: The higher pathologic complete response (pCR) after neoadjuvant chemoradiotherapy compared with neoadjuvant chemotherapy for locally advanced esophageal squamous cell carcinoma (ESCC) has not translated into significant gains in overall survival. Data on the long-term survival of patients who obtained a pCR after neoadjuvant chemotherapy are scarce. Therefore, this study aimed to evaluate the long-term prognosis and recurrence patterns in these patients. METHODS: The study enrolled patients with locally advanced ESCC after neoadjuvant chemotherapy followed by surgery in the authors' hospital between January 2007 and December 2020. The factors predictive of pCR were analyzed. Furthermore, propensity score-matching was performed for those who did and those who did not have a pCR using 1:5 ratio for a long-term survival analysis. Finally, the survival and recurrence patterns of patients obtaining pCR after neoadjuvant chemotherapy were analyzed. RESULTS: A pCR was achieved for 61 (8.70%) of the 701 patients in the study. Univariate analysis showed that the patients without alcohol drinking had a higher possibility of obtaining a pCR, although multivariate analysis failed to confirm the difference as significant. After propensity score-matching, the 5-year overall survival was 84.50% for the patients who had a pCR and 52.90% for those who did not (p < 0.001). Among the 61 patients with a pCR, 9 patients (14.80%) experienced recurrence, including 6 patients with locoregional recurrence and 3 patients with distant metastasis. CONCLUSION: Advanced ESCC patients with pCR after neoadjuvant chemotherapy had a favorable prognosis, yet some still experienced recurrence, particularly locoregional recurrence. Therefore, for this group of patients, regular follow-up evaluation also is needed.

Early Contrast-Enhanced MR for Diagnosing Complete Tumor Response of Locally Advanced Esophageal Squamous Cell Carcinoma After Neoadjuvant Therapy: A Retrospective Comparative Study.

BACKGROUND: This study assessed the performance of early contrast-enhanced magnetic resonance (ECE-MR) in the detecting of complete tumor response (ypT0) in patients with esophageal squamous cell carcinoma following neoadjuvant therapy. PATIENTS AND METHODS: Preoperative MR images of consecutive patients who underwent neoadjuvant therapy and surgical resection were reviewed retrospectively. The accuracy of ECE-MR and T2WI+DWI was evaluated by comparing the findings with pathological results. Receiver operating characteristic curve analysis was used to assess the diagnostic performance, and DeLong method was applied to compare the areas under the curves (AUC). Chi-squared analysis was conducted to explore the difference in pathological changes. RESULTS: A total of 198 patients (mean age 62.6 ± 7.8 years, 166 men) with 201 lesions were included. The AUC of ECE-MR was 0.85 (95% CI 0.79-0.90) for diagnosing ypT1-4, which was significantly higher than that of T2WI+DWI (AUC 0.69, 95% CI 0.63-0.76, p < 0.001). The diagnostic performance of both T2WI+DWI and ECE-MR improved with increasing tumor stage. The AUCs of ECE-MRI were higher in ypT1 and ypT2 tumors than T2WI+DWI. Degree 2-3 tumor-infiltrating lymphocytes and neutrophils were commonly seen in ypT0 tumors misdiagnosed by ECE-MR. CONCLUSIONS: Visual evaluation of ECE-MR is a promising diagnostic protocol for the detection of complete tumor response, especially for differentiation with early stage tumors. The accurate diagnosis of complete tumor response after neoadjuvant therapy using imaging modalities is of important significance for clinical decision-making for patients with esophageal squamous cell carcinoma. It is hoped that early contrast-enhanced MR will provide supportive advice for the development of individualized treatment options for patients.

Association between periodontal diseases and chronic obstructive pulmonary disease: Evidence from sequential cross-sectional and prospective cohort studies based on UK Biobank.

AIM: To investigate the association between periodontal diseases, airflow limitation and incident chronic obstructive pulmonary disease (COPD) in a large-scale prospective UK Biobank cohort. MATERIALS AND METHODS: Our approach comprised a cross-sectional study and a prospective cohort. Periodontal diseases were determined based on the participants' self-reported dental symptoms, including painful gums, bleeding gums and loose teeth. Logistic regression and Cox proportional hazards models were used to evaluate the association of periodontal diseases with airflow limitation and incident COPD in the cross-sectional study and the prospective cohort, respectively. RESULTS: The cross-sectional study involved 495,610 participants. Multivariable analysis found that periodontal diseases were significantly associated with airflow limitation (odds ratio = 1.036, 95% confidence interval [CI]: 1.015-1.059). The cohort study included 379,266 participants with a median follow-up period of 12.68 years. An elevated risk of incident COPD was associated with the presence of periodontal diseases (hazard ratio: 1.248, 95% CI: 1.174-1.326). The effect was consistent among subgroups, including baseline age (≤65 or >65 years), sex, smoking status and diabetes mellitus. CONCLUSIONS: Periodontal diseases are associated with airflow limitation and elevated COPD incidence. Maintaining good periodontal health in patients with chronic bronchitis and emphysema may help prevent the onset of COPD.

Achieving deep intratumoral penetration and multimodal combined therapy for tumor through algal photosynthesis.

BACKGROUND: Elevated interstitial fluid pressure within tumors, resulting from impaired lymphatic drainage, constitutes a critical barrier to effective drug penetration and therapeutic outcomes. RESULTS: In this study, based on the photosynthetic characteristics of algae, an active drug carrier (CP@ICG) derived from Chlorella pyrenoidosa (CP) was designed and constructed. Leveraging the hypoxia tropism and phototropism exhibited by CP, we achieved targeted transport of the carrier to tumor sites. Additionally, dual near-infrared (NIR) irradiation at the tumor site facilitated photosynthesis in CP, enabling the breakdown of excessive intratumoral interstitial fluid by generating oxygen from water decomposition. This process effectively reduced the interstitial pressure, thereby promoting enhanced perfusion of blood into the tumor, significantly improving deep-seated penetration of chemotherapeutic agents, and alleviating tumor hypoxia. CONCLUSIONS: CP@ICG demonstrated a combined effect of photothermal/photodynamic/starvation therapy, exhibiting excellent in vitro/in vivo anti-tumor efficacy and favorable biocompatibility. This work provides a scientific foundation for the application of microbial-enhanced intratumoral drug delivery and tumor therapy.

5-Methyl-cytosine stabilizes DNA but hinders DNA hybridization revealed by magnetic tweezers and simulations.

5-Methyl-cytosine (5mC) is one of the most important DNA modifications and plays versatile biological roles. It is well known that 5mC stabilizes DNA duplexes. However, it remains unclear how 5mC affects the kinetics of DNA melting and hybridization. Here, we studied the kinetics of unzipping and rezipping using a 502-bp DNA hairpin by single-molecule magnetic tweezers. Under constant loading rates, 5mC increases the unzipping force but counterintuitively decreases the rezipping force at various salt and temperature conditions. Under constant forces, the non-methylated DNA hops between metastable states during unzipping and rezipping, which implies low energy barriers. Surprisingly, the 5mC DNA can't rezip after fully unzipping unless much lower forces are applied, where it rezips stochastically in a one-step manner, which implies 5mC kinetically hinders DNA hybridization and high energy barriers in DNA hybridization. All-atom molecular dynamics simulations reveal that the 5mC kinetically hinders DNA hybridization due to steric effects rather than electrostatic effects caused by the additional methyl groups of cytosines. Considering the possible high speed of DNA unzipping and zipping during replication and transcription, our findings provide new insights into the biological roles of 5mC.

Gradient Nanoconfinement Facilitates Binding of Transcriptional Factor NF-κB to Histone- and Protamine-DNA Complexes.

Mechanically induced chromosome reorganization plays important roles in transcriptional regulation. However, the interplay between chromosome reorganization and transcription activities is complicated, such that it is difficult to decipher the regulatory effects of intranuclear geometrical cues. Here, we simplify the system by introducing DNA, packaging proteins (i.e., histone and protamine), and transcription factor NF-κB into a well-defined fluidic chip with changing spatical confinement ranging from 100 to 500 nm. It is uncovered that strong nanoconfinement suppresses higher-order folding of histone- and protamine-DNA complexes, the fracture of which exposes buried DNA segments and causes increased quantities of NF-κB binding to the DNA chain. Overall, these results reveal a pathway of how intranuclear geometrical cues alter the open/closed state of a DNA-protein complex and therefore affect transcription activities: i.e., NF-κB binding.

Serum Bile Acid Metabolites Predict the Therapeutic Effect of Mesalazine in Patients with Ulcerative Colitis.

Ulcerative colitis (UC) is a systematic chronic disease characterized by insufficient intestinal absorption, and mesalazine is a common medical treatment. In the present study, 20 normal healthy controls (NC group), 10 unmedicated UC patients (UC group), and 20 mesalazine-responsive and 20 mesalazine-nonresponsive UC patients were recruited. A total of 42 serum BA metabolites, including 8 primary bile acids and 34 secondary bile acids (SBAs), were quantitatively measured. Compared with the NC group, serum SBAs in the UC patients were significantly lower but increased after mesalazine therapy. Differences in the serum TDCA, DCA, GDCA-3S, 12-keto LCA, and GCDCA-3S metabolites were found between the UC and NC groups, with AUC values of 0.777, 0.800, 0.815, 0.775, and 0.740, respectively. Furthermore, we identified 12-keto LCA as a specific BA marker of UC and BA biomarkers of mesalazine responsiveness. It was concluded that serum SBAs were decreased in UC patients, and TDCA, DCA, GDCA-3S, 12-keto LCA, and GCDCA-3S might aid in the diagnosis of UC. The abundance of SBAs increased after the mesalazine therapy, and serum 12-keto LCA was identified as an alternative invasive biomarker associated with UC diagnosis and therapeutic response, thereby providing a new approach for the prediction of response to mesalazine therapy in UC patients.

Pre-operative oil ingestion reduces the probability of thoracic duct trunk ligation during esophagectomy.

Chylothorax is an important complication after esophagectomy. Ligation of the injured thoracic duct is the main method to prevent chylothorax after esophagectomy, but may be associated with adverse effects. Whether ligation of the injured tributary alone, keeping the main trunk intact, may suffice to prevent post-operative chylothorax is not well known. Since March 2017, 40 mL of olive oil was administered to patients posted for esophagectomy. We compared patients admitted between March 2017 and December 2019 with patients admitted between July 2014 and February 2017, who had not received pre-operative oil. The outcome measures were the need for thoracic duct main trunk or tributary ligation, development of chylothorax and missed ligation. There were 371 patients in the oil ingestion group and 308 patients in the standard control group. Chylothorax in the oil ingestion group was significantly lower than that in the standard control group (1.3% vs. 4.5%, P = 0.012). Chyle leak from thoracic duct tributaries was diagnosed in a significantly higher percentage (5.7% vs. 0.0%, P < 0.001) and missed ligation of the injured thoracic duct was significantly lower (0.3% vs. 3.9%, P = 0.002) in the oil ingestion group compared with the standard control group. The incidence of post-operative chylothorax was not statistically different (6.3% vs. 10.0%, P = 1.000) between the tributary and the trunk ligation group. Pre-operative oil ingestion can help visualize the thoracic duct trunk and its tributaries during esophagectomy. Thus, non-selected thoracic duct trunk ligation and missed ligation during esophagectomy can be reduced. Precise ligation of the injured tributary while the main trunk is intact can also prevent post-operative chylothorax.

Particle number size distributions and formation and growth rates of different new particle formation types of a megacity in China.

To understand the contribution of new particle formation (NPF) events to ambient fine particle pollution, measurements of particle size distributions, trace gases and meteorological conditions, were conducted at a suburban site (NJU) from October to December 2016 and at an industrial site (NUIST) from September to November 2015 in Nanjing. According to the temporal evolution of the particle size distributions, three types NPF events were observed: typical NPF (Type A), moderate NPF events (Type B) and strong NPF (Type C) events. The favorable conditions for Type A events included low relative humidity, low concentration of pre-existing particles, and high solar radiation. The favorable conditions of Type B events were similar to Type A, except for a higher concentration of pre-existing particles. Type C events were more likely to happen with the higher relative humidity, lower solar radiation and continuous growth of pre-existing particle concentration. The formation rate of 3 nm (J3) was the lowest for Type A events and highest for Type C events. In contrast, the growth rates of 10 nm and 40 nm particles were the highest for Type A, and lowest for Type C. Results show that NPF events with only higher J3 would lead to the accumulation of nucleation mode particles. Sulfuric acid was important for the formation of particles but had little effect on the growth of particle size.

[Comparison of therapeutic effects between holmium laser and plasma transurethral enucleation in the treatment of benign prostatic hyperplasia].

OBJECTIVE: Comparison of clinical efficacy between transurethral holmium laser prostate enucleation (two-way rendezvous and trenching method) and transurethral plasma enucleation. METHODS: A total of 483 patients with benign prostatic hyperplasia who were admitted to our hospital from December 2019 to December 2022 were randomly divided into an observation group (245 cases) and a control group (238 cases) using a random number table method. The observation group underwent transurethral holmium laser prostatectomy, while the control group underwent transurethral plasma prostatectomy,evaluate the efficacy of two surgical methods. RESULT: The IPSS symptom score, quality of life (QOL) score, maximum urinary flow rate (Qmax), residual urine volume (PVR) and other indicators were significantly improved in both groups after 6 months of surgery compared to before (P<0.05), and there was no statistically significant difference between the two groups (P>0.05). The incidence of postoperative complications in the observation group was significantly lower than that in the control group (P<0.05). There was no statistically significant difference in sexual function and retrograde ejaculation between the two groups of patients(P>0.05). CONCLUSION: Both surgical methods have good surgical efficacy, but compared with prostate plasma resection, holmium laser prostatectomy can reduce intraoperative bleeding in patients with BPH, effectively shorten catheter retention time, patient hospitalization time, and postoperative bladder flushing time, resulting in higher quality of life and safety.

Organizations of melittin peptides after spontaneous penetration into cell membranes.

The antimicrobial peptide, melittin, is a potential next-generation antibiotic because melittin can spontaneously form pores in bacterial cell membranes and cause cytoplasm leakage. However, the organizations of melittin peptides in cell membranes remain elusive, which impedes the understanding of the poration mechanism. In this work, we use coarse-grained and all-atom molecular dynamics (MD) simulations to investigate the organizations of melittin peptides during and after spontaneous penetration into DPPC/POPG lipid bilayers. We find that the peptides in lipid bilayers adopt either a transmembrane conformation or a U-shaped conformation, which are referred to as T- and U-peptides, respectively. Several U-peptides and/or T-peptides aggregate to form stable pores. We analyze a T-pore consisting of four T-peptides and a U-pore consisting of three U-peptides and one T-peptide. In both pores, peptides are organized in a manner such that polar residues face inward and hydrophobic residues face outward, which stabilizes the pores and produces water channels. Compared with the U-pore, the T-pore has lower energy, larger pore diameter, and higher permeability. However, the T-pore occurs less frequently than the U-pore in our simulations, probably because the formation of the T-pore is kinetically slower than the U-pore. The stability and permeability of both pores are confirmed by 300 ns all-atom MD simulations. The peptide organizations obtained in this work should deepen the understanding of the stability, poration mechanism, and permeability of melittin, and facilitate the optimization of melittin to enhance the antibacterial ability.

Forming a Double-Helix Phase of Single Polymer Chains by the Cooperation between Local Structure and Nonlocal Attraction.

Double-helix structures, such as DNA, are formed in nature to realize many unique functions. Inspired by this, researchers are pursuing strategies to design such structures from polymers. A key question is whether the double helix can be formed from the self-folding of a single polymer chain without specific interactions. Here, using Langevin dynamics simulation and theoretical analysis, we find that a stable double-helix phase can be achieved by the self-folding of single semiflexible polymers as a result of the cooperation between local structure and nonlocal attraction. The critical temperature of double-helix formation approximately follows T^{cri}∼ln(k_{θ}) and T^{cri}∼ln(k_{τ}), where k_{θ} and k_{τ} are the polymer bending and torsion stiffness, respectively. Furthermore, the double helix can exhibit major and minor grooves due to symmetric break for better packing. Our results provide a novel guide to the experimental design of the double helix.

Multivalent Cations Reverse the Twist-Stretch Coupling of RNA.

When stretched, both DNA and RNA duplexes change their twist angles through twist-stretch coupling. The coupling is negative for DNA but positive for RNA, which is not yet completely understood. Here, our magnetic tweezers experiments show that the coupling of RNA reverses from positive to negative by multivalent cations. Combining with the previously reported tension-induced negative-to-positive coupling reversal of DNA, we propose a unified mechanism of the couplings of both RNA and DNA based on molecular dynamics simulations. Two deformation pathways are competing when stretched: shrinking the radius causes positive couplings but widening the major groove causes negative couplings. For RNA whose major groove is clamped by multivalent cations and canonical DNA, their radii shrink when stretched, thus exhibiting positive couplings. For elongated DNA whose radius already shrinks to the minimum and canonical RNA, their major grooves are widened when stretched, thus exhibiting negative couplings.

Discovery of a Novel Macrocyclic ATP Citrate Lyase Inhibitor.

ATP citrate lyase (ACLY) is an important metabolic enzyme involved in the synthesis of fatty acid and cholesterol. The inhibition of ACLY is considered as a promising therapeutic strategy for various metabolic diseases and numerous malignancies. In this study, a novel macrocyclic compound 2 has been identified as a potent ACLY inhibitor with the "ring closing" strategy for conformational restriction based on NDI-091143. It showed potent ACLY inhibitory activity and binding affinity comparable to the positive control. Furthermore, compared with the positive control (T1/2 = 3.36 min), the metabolic stability of 2 in HLMs (T1/2 = 531.22 min) was significantly improved. All of these results characterized 2 as a promising lead compound worthy of further study.

Assessment of carbonaceous aerosols in suburban Nanjing under air pollution control measures: Insights from long-term measurements.

The concentrations of organic carbon (OC) and elemental carbon (EC) in fine particulate matter (PM2.5) were analyzed using a semicontinuous carbon analyzer to characterize their carbonaceous components at the Nanjing University site from August 2013 to December 2018. OC was divided by the minimum R squared (MRS) method into primary organic carbon (POC) and secondary organic carbon (SOC). The results showed that annual mean POC and EC concentrations declined from 10.00 to 3.62 µg m-3 and from 6.73 to 3.40 µg m-3, respectively, during 2013-2018. The apparent reduction in POC and EC concentrations indicated that the implementation of air pollution control measures helped reduce carbonaceous aerosol pollution. Higher concentrations of POC and EC were recorded during the cold season and lower in the warm season. The annual mean SOC concentrations varied between 4.35 and 3.18 µg m-3 from 2013 to 2018. Elevated SOC was observed during the warm season, most likely attributable to the enhanced photochemical activity at high temperatures. Regarding the diurnal variation, the high concentrations of POC and EC were observed at night and in the morning due to stronger primary emissions and accumulations of pollutants with low boundary-layer heights, while the peak of SOC was observed at approximately noon due to the increases in photochemical activity. Nonparametric wind regression analysis showed the higher concentrations of POC, SOC and EC in the northwesterly, southwesterly to southeasterly, and southwesterly winds with high speeds. Concentration-weighted trajectory (CWT) analysis suggests that the areas with potentially high contributions to POC and EC changed from the north to the western areas of China, and that northern China played an increasingly important role in the SOC concentration of Nanjing. These results demonstrate that controlling emissions from the western and the northern areas in China may further alleviate carbonaceous aerosol pollution in Nanjing.

Correlation between serum levels of reproductive hormones and testicular spermatogenic function in men with azoospermia.

To investigate the serum levels of reproductive hormones in men with azoospermia and explore the correlation between abnormal reproductive hormones and the results of testicular biopsy and seminiferous extraction. The serum levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone (T), and pituitary prolactin (PRL), were measured by Radio immunoassay. Testicular biopsy was used to determine whether patient's had spermatozoa. Spearman's correlation analysis was used to analyse the correlation between LH, FSH, testicular volume, and spermatogenic function. Receiver operator characteristic (ROC) curves were used to evaluate the efficacy and significance of LH and FSH for the detection of spermatozoa and copy number variation sequencing (CNV-seq). Compared with the control group, the serum levels of FSH and LH in the azoospermia group were significantly up-regulated (p < 0.001). Prolactin (PRL) and testosterone levels did not differ significantly between the two groups (p > 0.05). The serum levels of FSH and LH were negatively correlated with testicular spermatogenic function and testicular volume. The areas under the ROC curves for determining FSH and LH potency by testicular biopsy with or without spermatozoa were 0.640 and 0.622, respectively. The areas under the ROC curves for the potency of FSH and LH, as judged by CNV detection results, were 0.523 and 0.534, respectively. Serum levels of FSH and LH are associated with azoospermia and may be of predictive significance in the clinical setting for the acquisition of spermatozoa by testicular biopsy.

DNA Knot Malleability in Single-Digit Nanopores.

Knots in long DNA molecules are prevalent in biological systems and serve as a model system for investigating static and dynamic properties of biopolymers. We explore the dynamics of knots in double-stranded DNA in a new regime of nanometer-scale confinement, large forces, and short time scales, using solid-state nanopores. We show that DNA knots undergo isomorphic translocation through a nanopore, retaining their equilibrium morphology by swiftly compressing in a lateral direction to fit the constriction. We observe no evidence of knot tightening or jamming, even for single-digit nanopores. We explain the observations as the malleability of DNA, characterized by sharp buckling of the DNA in nanopores, driven by the transient disruption of base pairing. Our molecular dynamics simulations support the model. These results are relevant not only for the understanding of DNA packing and manipulation in living cells but also for the polymer physics of DNA and the development of nanopore-based sequencing technologies.