Engineering of a DNAzyme-Based dimeric G-quadruplex rolling circle amplification for robust analysis of lead ion

Detecting heavy metal pollution, particularly lead ion (Pb2⁺) contamination, is imperative for safeguarding public health. In this study, we introduced an innovative approach by integrating DNAzyme with rolling circle amplification (RCA) to propose an amplification sensing method termed DNAzyme-based dimeric-G-quadruplex (dimer-G4) RCA. This sensing approach allows for precise and high-fidelity Pb2⁺ detection. Strategically, in the presence of Pb2⁺, the DNAzyme undergoes substrate strand (S-DNA) cleavage, liberating its enzyme strand (E-DNA) to prime isothermal amplification. This initiates the RCA process, producing numerous dimer-G-Quadruplexes (dimer-G4) as the signal reporting transducers. Compared to conventional strategies using monomeric G-quadruplex (mono-G4) as the reporting transducers, these dimer-G4 structures exhibit significantly enhanced fluorescence when bound with Thioflavin T (ThT), offering superior target signaling ability for even detection of Pb2⁺ at low concentration. Conversely, in the absence of Pb2⁺, the DNAzyme structure remains intact so that no primers can be produced to cause the RCA initiation. This nucleic acid amplification-based Pb2⁺ detection method combing with the high specificity of DNAzymes for Pb2⁺ recognition ensures highly sensitive detection of Pb2+ with a detection limit of 0.058 nM, providing a robust tool for food safety analysis and environmental monitoring.

Advances, challenges, and opportunities for food safety analysis in the isothermal nucleic acid amplification/CRISPR-Cas12a era

Global food safety stands out as a prominent public concern, affecting populations worldwide. The recurrent challenge of food safety incidents reveals the need for a robust inspection framework. In recent years, the integration of isothermal nucleic acid amplification with CRISPR-Cas12a techniques has emerged as a promising tool for molecular detection of food hazards, presenting next generation of biosensing for food safety detection. This paper provides a comprehensive review of the current state of research on the synergistic application of isothermal nucleic acid amplification and CRISPR-Cas12a technology in the field of food safety. This innovative combination not only enriches the analytical tools, but also improving assay performance such as sensitivity and specificity, addressing the limitations of traditional methods. The review summarized various detection methodologies by the integration of isothermal nucleic acid amplification and CRISPR-Cas12a technology for diverse food safety concerns, including pathogenic bacterium, viruses, mycotoxins, food adulteration, and genetically modified foods. Each section elucidates the specific strategies employed and highlights the advantages conferred. Furthermore, the paper discussed the challenges faced by this technology in the context of food safety, offering insightful discussions on potential solutions and future prospects.

An artificial protein modulator reprogramming neuronal protein functions

Reversible protein phosphorylation, regulated by protein phosphatases, fine-tunes target protein function and plays a vital role in biological processes. Dysregulation of this process leads to aberrant post-translational modifications (PTMs) and contributes to disease development. Despite the widespread use of artificial catalysts as enzyme mimetics, their direct modulation of proteins remains largely unexplored. To address this gap and enable the reversal of aberrant PTMs for disease therapy, we present the development of artificial protein modulators (APROMs). Through atomic-level engineering of heterogeneous catalysts with asymmetric catalytic centers, these modulators bear structural similarities to protein phosphatases and exhibit remarkable ability to destabilize the bridging μ3-hydroxide. This activation of catalytic centers enables spontaneous hydrolysis of phospho-substrates, providing precise control over PTMs. Notably, APROMs, with protein phosphatase-like characteristics, catalytically reprogram the biological function of α-synuclein by directly hydrolyzing hyperphosphorylated α-synuclein. Consequently, synaptic function is reinforced in Parkinson's disease. Our findings offer a promising avenue for reprogramming protein function through de novo PTMs strategy.

Engineering of an adaptive tandem CRISPR/Cas12a molecular amplifier permits robust analysis of Vibrio parahaemolyticus

Seeking new molecular diagnostic method for pathogenic bacteria detection is of utmost importance for ensuring food safety and protecting human health. Herein, we have engineered an adaptive tandem CRISPR/Cas12a molecular amplifier specifically designed for robust analysis of vibrio parahaemolyticus (V. parahaemolyticus), one of the most harmful pathogens. Our strategy involves the integration of three crucial processes: recombinase polymerase amplification (RPA) for copy number amplification, terminal deoxynucleotidyl transferase (TdT) for template-free strand elongation, and CRISPR/Cas12a-mediated trans-cleavage of a reporter molecule. By combining these processes, the target genomic DNA extracted from V. parahaemolyticus is able to activate many CRISPR/Cas12a units (CRISPR/Cas12an) simultaneously, resulting in a greatly amplified target signal to indicate the presence and concentration of V. parahaemolyticus. This unique model offers more advantages compared to traditional amplification models that use one RPA amplicon to activate one CRISPR/Cas12a unit. Under optimized conditions, our method enables the detection of target V. parahaemolyticus within a linear range of 1 × 102-1 × 107 CFU/mL, with an impressive limit of detection as low as 12.4 CFU/mL. It is conceivable that the adaptive tandem CRISPR/Cas12a molecular amplifier could be adapted as routine diagnostic kits in future for in-field detection of pathogens.

A Selective Nano Cell Cycle Checkpoint Inhibitor Overcomes Leukemia Chemoresistance

Cell cycle checkpoint activation promotes DNA damage repair, which is highly associated with the chemoresistance of various cancers including acute myeloid leukemia (AML). Selective cell cycle checkpoint inhibitors are strongly demanded to overcome chemoresistance, but remain unexplored. A selective nano cell cycle checkpoint inhibitor (NCCI: citric acid capped ultra-small iron oxide nanoparticles) that can catalytically inhibit the cell cycle checkpoint of AML to boost the chemotherapeutic efficacy of genotoxic agents is now reported. NCCI can selectively accumulate in AML cells and convert H2 O2 to • OH to cleave heat shock protein 90, leading to the degradation of ataxia telangiectasia and Rad3-related proteinand checkpoint kinase 1, and the subsequent dysfunction of the G2/M checkpoint. Consequently, NCCI revitalizes the anti-AML efficacy of cytarabine that is previously ineffective both in vitro and in vivo. This study offers new insights into designing selective cell cycle checkpoint inhibitors for biomedical applications.

[A multicenter epidemiological study of acute bacterial meningitis in children]

Objective: To analyze the clinical epidemiological characteristics including composition of pathogens , clinical characteristics, and disease prognosis acute bacterial meningitis (ABM) in Chinese children. Methods: A retrospective analysis was performed on the clinical and laboratory data of 1 610 children <15 years of age with ABM in 33 tertiary hospitals in China from January 2019 to December 2020. Patients were divided into different groups according to age,<28 days group, 28 days to <3 months group, 3 months to <1 year group, 1-<5 years of age group, 5-<15 years of age group; etiology confirmed group and clinically diagnosed group according to etiology diagnosis. Non-numeric variables were analyzed with the Chi-square test or Fisher's exact test, while non-normal distrituction numeric variables were compared with nonparametric test. Results: Among 1 610 children with ABM, 955 were male and 650 were female (5 cases were not provided with gender information), and the age of onset was 1.5 (0.5, 5.5) months. There were 588 cases age from <28 days, 462 cases age from 28 days to <3 months, 302 cases age from 3 months to <1 year of age group, 156 cases in the 1-<5 years of age and 101 cases in the 5-<15 years of age. The detection rates were 38.8% (95/245) and 31.5% (70/222) of Escherichia coli and 27.8% (68/245) and 35.1% (78/222) of Streptococcus agalactiae in infants younger than 28 days of age and 28 days to 3 months of age; the detection rates of Streptococcus pneumonia, Escherichia coli, and Streptococcus agalactiae were 34.3% (61/178), 14.0% (25/178) and 13.5% (24/178) in the 3 months of age to <1 year of age group; the dominant pathogens were Streptococcus pneumoniae and the detection rate were 67.9% (74/109) and 44.4% (16/36) in the 1-<5 years of age and 5-<15 years of age . There were 9.7% (19/195) strains of Escherichia coli producing ultra-broad-spectrum β-lactamases. The positive rates of cerebrospinal fluid (CSF) culture and blood culture were 32.2% (515/1 598) and 25.0% (400/1 598), while 38.2% (126/330)and 25.3% (21/83) in CSF metagenomics next generation sequencing and Streptococcus pneumoniae antigen detection. There were 4.3% (32/790) cases of which CSF white blood cell counts were normal in etiology confirmed group. Among 1 610 children with ABM, main intracranial imaging complications were subdural effusion and (or) empyema in 349 cases (21.7%), hydrocephalus in 233 cases (14.5%), brain abscess in 178 cases (11.1%), and other cerebrovascular diseases, including encephalomalacia, cerebral infarction, and encephalatrophy, in 174 cases (10.8%). Among the 166 cases (10.3%) with unfavorable outcome, 32 cases (2.0%) died among whom 24 cases died before 1 year of age, and 37 cases (2.3%) had recurrence among whom 25 cases had recurrence within 3 weeks. The incidences of subdural effusion and (or) empyema, brain abscess and ependymitis in the etiology confirmed group were significantly higher than those in the clinically diagnosed group (26.2% (207/790) vs. 17.3% (142/820), 13.0% (103/790) vs. 9.1% (75/820), 4.6% (36/790) vs. 2.7% (22/820), χ²=18.71, 6.20, 4.07, all P<0.05), but there was no significant difference in the unfavorable outcomes, mortility, and recurrence between these 2 groups (all P>0.05). Conclusions: The onset age of ABM in children is usually within 1 year of age, especially <3 months. The common pathogens in infants <3 months of age are Escherichia coli and Streptococcus agalactiae, and the dominant pathogen in infant ≥3 months is Streptococcus pneumoniae. Subdural effusion and (or) empyema and hydrocephalus are common complications. ABM should not be excluded even if CSF white blood cell counts is within normal range. Standardized bacteriological examination should be paid more attention to increase the pathogenic detection rate. Non-culture CSF detection methods may facilitate the pathogenic diagnosis.

Toxin-Enabled "On-Demand" Liposomes for Enhanced Phototherapy to Treat and Protect against Methicillin-Resistant Staphylococcus aureus Infection

An effective therapeutic strategy against methicillin-resistant Staphylococcus aureus (MRSA) that does not promote further drug resistance is highly desirable. While phototherapies have demonstrated considerable promise, their application toward bacterial infections can be limited by negative off-target effects to healthy cells. Here, a smart targeted nanoformulation consisting of a liquid perfluorocarbon core stabilized by a lipid membrane coating is developed. Using vancomycin as a targeting agent, the platform is capable of specifically delivering an encapsulated photosensitizer along with oxygen to sites of MRSA infection, where high concentrations of pore-forming toxins trigger on-demand payload release. Upon subsequent near-infrared irradiation, local increases in temperature and reactive oxygen species effectively kill the bacteria. Additionally, the secreted toxins that are captured by the nanoformulation can be processed by resident immune cells to promote multiantigenic immunity that protects against secondary MRSA infections. Overall, the reported approach for the on-demand release of phototherapeutic agents into sites of infection could be applied against a wide range of high-priority pathogens.

A KPV-binding double-network hydrogel restores gut mucosal barrier in an inflamed colon

Ulcerative colitis (UC) usually occurs in the superficial mucosa of the colorectum. Here, a double-network hydrogel (PMSP) was constructed from maleimided γ-polyglutamic acid and thiolated γ-polyglutamic acid through crosslinking of thiol-maleimide and self-oxidized thiols. PMSP with a negative charge specifically adhered to the inflamed mucosa with positively charged proteins rather than to the healthy mucosa. PMSP exhibited good mechanical strength with storage modulus (G') of 17.6 Pa and a linear viscoelastic region (LVR) of 107.2% strain. Moreover, PMSP showed a stronger bio-adhesive force toward the inflamed tissue-mimicking substrate than toward its healthy counterpart. In vivo imaging confirmed that PMSP specifically adhered to the inflamed colonic mucosa of rats with TNBS-induced UC. KPV (Lys-Pro-Val) as a model drug was easily captured by PMSP through electrostatic interactions, thus retaining its bioactivity for a longer time under high temperature conditions. Moreover, the alleviating effect of KPV on rats with TNBS-induced colitis was significantly improved by PMSP after intracolonic administration. The epithelial barrier of the colon also effectively recovered following PMSP-KPV treatment. PMSP-KPV also modulated the gut flora, markedly augmenting the abundance of beneficial microorganisms in gut homeostasis. The mechanism by which PMSP-KPV induces a therapeutic effect may be associated with the inhibition of oxidative stress. Conclusively, the PMSP hydrogel seems to be a promising rectal delivery system for the therapy of UC. STATEMENT OF SIGNIFICANCE: Ulcerative colitis (UC) is a chronic and relapsing disease of the gastrointestinal tract. A key therapeutic approach to treat UC is to repair the mucosal barriers. Here, a double-network hydrogel (PMSP) was constructed from maleimided and thiolated γ-polyglutamic acid through crosslinking of thiol-maleimide and self-oxidized thiols. The negatively charged PMSP specifically adhered to the inflamed colon rather than its healthy counterpart and was retained for a longer time. KPV as a model drug was easily captured by PMSP, which provided better stability to KPV when exposed to high temperature of 50 °C. The epithelial mucosal barrier of the colon was effectively recovered by the rectal administration of PMSP-KPV to rats with TNBS-induced UC. Moreover, PMSP-KPV modulated the gut flora of colitic rats, markedly augmenting the abundance of beneficial microorganisms. Conclusively, PMSP seems to be a promising rectal delivery system for UC therapy.

[World Health Organization guidance Ethical and Governance of Artificial Intelligence for health and implications for China]

With the explosive growth of deep learning and big data technology, artificial intelligence has penetrated into various fields of medical and health care, bringing efficient and high-quality health services to patients, but also a series of ethical and social governance issues have emerged. In order to avoid and eliminate the foreseeable ethical risks and governance challenges in the development of medical artificial intelligence, the World Health Organization (WHO) first released the Ethical and Governance of Artificial Intelligence for Health guidance on June 28, 2021, aimed to provide a framework for ethical guidelines on the deployment of artificial intelligence in clinical practice. At present, there are still shortcomings and this paper takes Healthy China 2030 agenda and the WHO guidelines as strategic ideas, and proposes to shape a consensus on the ethics of medical artificial intelligence, establish rules for human subjects and ownership of responsibilities, improve the legal and regulatory system, and determine human decision-making and moral subject status, taking into account the cultivation of interdisciplinary talents' ethical literacy and other Chinese inspirations are expected to promote the development of medical artificial intelligence ethics governance.

[WHO global strategy on digital health and its implications to China]

The World Health Organization (WHO) released the global strategy report on digital health (2020-2025) in Geneva in 2019, which established the priority of the digital health strategy and formulated strategic objectives, guiding principles, action framework and implementation plans to promote the development of global digital health, and to achieve universal health coverage and the health-related sustainable development goals. Despite China's rapid development in the field of digital health, there is still a big gap between the realization of the goal of digital health. Therefore, it is urgent to grasp the major historical opportunity and step into a new era of digital health with the support of digital technology platform.

Self-Cross-Linked Hydrogel of Cysteamine-Grafted γ-Polyglutamic Acid Stabilized Tripeptide KPV for Alleviating TNBS-Induced Ulcerative Colitis in Rats

KPV (Lys-Pro-Val), which is a tripeptide derived from α-MSH (α-melanocyte-stimulating hormone), has an anti-inflammatory effect on colitis. However, KPV solution is very unstable when rectally administered, compromising its therapeutic efficacy. Herein, cysteamine-grafted γ-polyglutamic acid (SH-PGA) was synthesized by conjugating cysteamine with the carboxyl groups of γ-PGA. The synthesized SH-PGA has the thiol grafting amount of 4.5 ± 0.3 mmol/g. Without the use of the cross-linker, the SH-PGA hydrogel with 4% of the polymer was formed by self-cross-linking of thiol groups. Moreover, the formation of the SH-PGA hydrogel was not affected by KPV. The KPV/SH-PGA hydrogel presented higher elastic modulus (G') than the corresponding viscous modulus (G″) at 0.01-10 Hz, exhibiting good mechanical stability. The KPV/SH-PGA hydrogel presented a shear-thinning behavior, which was helpful for rectal administration. Only 30% of KPV was released from the KPV/SH-PGA hydrogel within 20 min, followed by a sustained-release behavior. Importantly, the stability of KPV in the SH-PGA hydrogel was obviously enhanced, which was presented by detecting its anti-inflammatory activity and promoting cell migration potential after 2 h of exposure to 37 °C. The enhanced therapeutic effect of the KPV/SH-PGA hydrogel on colitis was confirmed on 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced ulcerative colitis rats. The colitis symptoms including body weight loss and the disease activity index score were obviously attenuated by rectally administering the KPV/SH-PGA hydrogel. Besides, the KPV/SH-PGA hydrogel treatment prevented the colon shortening of TNBS-infused rats and decreased the colonic myeloperoxidase level. The morphology of the colon including the epithelial barrier, crypt, and intact goblet cells was recovered after KPV/SH-PGA hydrogel treatment. Besides, the KPV/SH-PGA hydrogel decreased the expression of proinflammatory cytokines such as tumor necrosis factor α and interleukin 6. Collectively, the KPV/SH-PGA hydrogel may provide a promising strategy for the treatment of ulcerative colitis.

[Clinical effects of follicle unit extraction transplantation combined with recombinant bovine basic fibroblast growth factor and minoxidil in the treatment of secondary cicatricial alopecia]

Objective: To explore the clinical effects of follicle unit extraction (FUE) transplantation combined with recombinant bovine basic fibroblast growth factor (rb-bFGF) gel and minoxidil tincture in treating secondary cicatricial alopecia (hereinafter referred to as cicatricial alopecia). Methods: A retrospective observational study was conducted. According to the different treatment methods, 50 cicatricial alopecia patients who met the inclusion criteria and only underwent FUE transplantation in the First Affiliated Hospital of Air Force Medical University from March 2013 to April 2017 were recruited into FUE alone group (26 males and 24 females, aged (28±13) years), and 50 cicatricial alopecia patients who met the inclusion criteria and underwent FUE transplantation+rb-bFGF gel during 1 to 14 days after surgery+minoxidil tincture during 15 to 180 days after surgery in this hospital from May 2017 to April 2020 were recruited into FUE+rb-bFGF+minoxidil group (32 males and 18 females, aged (27±9) years). Hair loss rates in post surgery month (PSM) 3 and 6, hair survival rates and satisfaction rates of patients in PSM 12, and the adverse effect rates of patients in the 2 groups within PSM 12 were observed and calculated. Data were statistically analyzed with chi-square test, Fisher's exact probability test, and independent sample t test. Results: In PSM 3 and 6, the hair loss rates of patients in FUE alone group were significantly higher than those in FUE+rb-bFGF+minoxidil group, respectively (t=70.850, 42.610, P<0.01). In PSM 12, the hair survival rate of patients in FUE+rb-bFGF+minoxidil group was (91.0±2.8)%, which was significantly higher than (80.9±6.9)% in FUE alone group (t=9.665, P<0.01). In PSM 12, 25 patients were very satisfied, 12 patients were fairly satisfied, 10 patients were slightly satisfied, 2 patients were not satisfied, and 1 patient was very unsatisfied in FUE alone group; 42 patients were very satisfied, 5 patients were fairly satisfied, and 3 patients were slightly satisfied in FUE+rb-bFGF+minoxidil group. The satisfaction rate of patients in FUE alone group was 74% (37/50), which was significantly lower than 94% (47/50) in FUE+rb-bFGF+minoxidil group (P<0.01). Within PSM 12, compared with those in FUE+rb-bFGF+minoxidil group, the incidence rates of folliculitis, abnormal growth direction, and skin necrosis in transplant site were not obviously changed in FUE alone group (P>0.05), while the incidence of scar in donor site was significantly higher (P<0.05). Conclusions: Compared with FUE transplantation alone, FUE transplantation combined with rb-bFGF and minoxidil can reduce the hair loss rate, improve the hair survival rate and the satisfaction rate of patients with cicatricial alopecia after FUE transplantation, with less adverse effects, thus are good for cicatricial alopecia treatment.

Liraglutide regulates proliferation, differentiation, and apoptosis of preosteoblasts through a signaling network of Notch/Wnt/Hedgehog signaling pathways

OBJECTIVE

This study aims to investigate whether liraglutide can affect proliferation, osteogenic differentiation and serum deprivation-induced apoptosis of preosteoblast cell line MC3T3-E1 through the Notch, Wnt/β-catenin, and Hedgehog (Hh) signaling pathways.

MATERIALS AND METHODS

MC3T3-E1 cells were exposed to different treatments (via Notch inhibitor DAPT, an Hh inhibitor cyclopamine, or serum deprivation) or transfections of different siRNAs (targeting glucagon-like peptide-1 receptor (GLP-1R), β-catenin, or Gli1) in the presence or absence of 100 nM liraglutide. Cell proliferation, mRNA levels of osteogenic differentiation-related genes, mRNA and protein levels of the Notch and Hh signaling pathway proteins, and apoptosis-related proteins were assessed.

RESULTS

Liraglutide significantly increased proliferation of MC3T3-E1 cells, expression levels of the Notch and Hh signaling pathway proteins and β-catenin, and mRNA levels of osteogenic differentiation-related genes and TCF7L2. Moreover, liraglutide promoted a translocation of β-catenin, increased a ratio of Bcl-2/Bax proteins, reduced serum deprivation-induced apoptosis of MC3T3-E1 cells, and a ratio of caspase-3/procaspase-3. However, a cotreatment with liraglutide and DAPT reversed the alterations. A cyclopamine treatment and knockdowns of GLP-1R, Gli1, and β-catenin significantly reduced the expression of Notch proteins. Furthermore, the knockdown of GLP-1R, β-catenin, or Gli1 significantly increased apoptosis, which could be inhibited by liraglutide.

CONCLUSIONS

In summary, liraglutide can promote proliferation and differentiation of MC3T3-E1 cells, and inhibit their serum deprivation-induced apoptosis by activating both the Notch and Hh signaling pathways involving β-catenin and Gli1. These results provide a therapeutic foundation that patients with diabetes and osteoporosis may be cured with treatments of liraglutide.

Temperature-sensitive hydrogel for rectal perfusion improved the therapeutic effect of Kangfuxin liquid on DSS-induced ulcerative colitis mice: The inflammation alleviation and the colonic mucosal barriers repair

Kangfuxin liquid (KFX) is a Chinese medicine extracted from Periplaneta americana dried worms, which presented the bioactive functions of anti-inflammation and promoting the gastrointestinal mucosal barriers repair. But the low availability of KFX exposed to the distal colon affects its therapeutic effect on ulcerative colitis. Herein, an in situ hydrogel containing KFX was designed by using temperature-sensitive poloxamer 407 (P-407) as material for rectal administration. Three KFX-P formulations with different P407 concentrations (17%, 20% and 25%) were designed and screened by detecting the gelation time, gelation temperature and mechanical strength of hydrogel. P407 in these formulations was able to be completely dissolved in KFX at 4 ℃ and then was in situ gelled at 37 ℃ to form a semisolid hydrogel. Moreover, the gelation time, the gelation temperature and the mechanical strength of KFX-P hydrogel are highly dependent on P407 concentration. With P407 concentration increasing, both the gelation time and gelation temperature of KFX-P accordingly decreased and the gelation temperature range becomes narrowed; while the mechanical strength increased. KFX-P-20% displayed the moderate gelation temperature (28-30 ℃), the short gelation time (26 s) and the moderate mechanical strength (G' = 4.2 × 10³ Pa), which was chosen for animal study. Thereafter, ulcerative colitis mice model (UC) was established by dextran sulfate sodium (DSS) and the therapeutic effect of KFX-P on UC was evaluated by inflammation symptoms relief, colon length, colonic MPO level and colonography. After rectal administration of KFX or KFX-P, the symptoms including diarrhea and hematochezia (DAI scores), weight loss and spleen swelling were significantly hindered. Meanwhile, the colonic MPO level in these groups was significantly decreased in comparison with PBS treatment. But the therapeutic effect of KFX-P was better than KFX. Besides, the morphology and mucosal barrier of colon were evaluated by HE staining, ZO-1 and claudin-5 staining. The mucosa epithelium layer, crypt, muscle layer mucosa and submucosa were also well repaired after KFX-P treatment. The strong fluorescence of ZO-1 and claudin-5 were uniformly distributed along the whole epithelial mucosa after KFX-P treatment, indicating the effective repairing of the colonic mucosal barrier. Collectively, the temperature-sensitive KFX-P for rectal delivery could effectively promote the repair of the colon mucosal barrier and inhibit the colonic inflammation in DSS-induced mice, which may be a potential strategy for UC treatment.

[Design and clinical application of goal-oriented retroperitoneoscopic adrenalectomy]

Objective: To investigate the goal-oriented retroperitoneoscopic adrenalectomy and report the initial experiment. Methods: A total of 102 patients were selected to our clinic experiment, and performed retroperitoneoscopic adrenalectomy with the new method. including adrenal cortex adenoma 76 cases, phaochromocytoma 12 cases, adrenal cyst 6 cases, myelolipoma 4 cases, gangliocytoma 1 case and corticohyperplassia 3 cases. The mean diameter of the tumors was 2.8 cm (0.5-5.8 cm). The operative procedure was briefly described as such, with ultrasound guiding, a needle was punched percutaneously up to the adrenal mass or the renal upper pole from lateral to posterior axillary line just below the inferior border of the 12th rib. labeled the pathway of the needle with methylene blue. Along the way of the needle, a 12 mm port was introduced into the retroperitoneal space with closed method, and the laparoscope with a working tunnel was introduced to make a tunnel along the label up to the adrenal for finally removing it. Additional port should be used when it was needed in the procedure. Results: The procedures of all patients were successful, and 10 patients were performed with only one port, 81 patients with two ports, 11 patients with three ports. The operative duration was 49 (31-115) min, the average blood loss was 38 (0-260) ml. There was no transition to open surgery and no perioperative complications. The length of postoperative hospital stay was 4.1 d (2-7 d). 98 patients were available for follow-up of 16.5 months (1-38 months), no complication was found. Conclusions: The new method of retroperitoneoscopic adrenalectomy is feasible and safe for renal masses, and compared to the conventional method, it may be less trauma to the abdominal wall and retropertoneal tissue, and it was also better on cosmetics.

Correction of Hyperglycemia in Diabetic Rats With the Use of Microencapsulated Young Market Pig Islets

OBJECTIVE

The aim of this work was to investigate the transplantation efficacy of microencapsulated young market pig islets in a diabetic rat model.

METHODS

Islets were isolated and purified from young market pigs obtained from a local slaughterhouse. The islets were encapsulated in barium alginate and subjected to a glucose-induced insulin release functional assay in culture. Microencapsulated islets were transplanted into diabetic Sprague-Dawley rats and removed after 30 days for histologic examination.

RESULTS

The mean islet equivalent (IEQ) yield per gram of digested tissue was 3,125 ± 617 IEQ/g after isolation and 2,618 ± 917 IEQ/g after purification, respectively. Host rats' blood glucose concentrations normalized (from 22.3 ± 2.7 mmol/L to 5.1 ± 0.67 mmol/L) following encapsulated islet transplantation. After graft removal, hyperglycemia recurred in the rats, indicating that the grafts were responsible for maintaining euglycemia. Histology revealed viable islets in the capsules 30 days after graft removal. Immunolabeling of insulin verified that β-cells within the capsules remained well granulated. No fibrosis or immune cells were found in histopathology.

CONCLUSIONS

Barium alginate encapsulation of young market pig islets can normalize glucose regulation in diabetic rats without fibrosis or an immunologic response.

A method for characterising human intervertebral disc glycosaminoglycan disaccharides using liquid chromatography-mass spectrometry with multiple reaction monitoring

Intervertebral disc (IVD) degeneration results in the depletion of proteoglycans and glycosaminoglycans (GAGs), which can lead to structural and mechanical loss of IVD function, ingrowth of nociceptive nerve fibres and eventually discogenic pain. Specific GAG types as well as their disaccharide patterns can be predictive of disease and degeneration in several tissues but have not been comprehensively studied within the IVD. A highly sensitive mass spectrometry based technique with multiple reaction monitoring (MRM) was used to provide characterisation of chondroitin sulphate (CS), hyaluronic acid (HA), heparan sulphate (HS) and their disaccharide sulphation patterns across different anatomical regions of human IVDs. Principal component analysis further distinguished important regional variations and proposed potential ageing variations in GAG profiles. CS was the GAG in greatest abundance in the IVD followed by HA and HS. Principal component analysis identified clear separation of GAG profiles between nucleus pulposus and annulus fibrosus in young and old specimens. Distinct patterns of predominantly expressed disaccharides of CS and HS between young and old IVD samples, provided preliminary evidence that important alterations in disaccharides occur within IVDs during ageing. This technique offered a novel approach to identify and quantify specific GAG disaccharides in human IVDs and the data presented were the first to offer insight into the spatial distribution as well as association with ageing of GAGs and GAG disaccharide sulphation patterns across the human IVD.

Effects of dl-3-n-butylphthalide on serum VEGF and bFGF levels in acute cerebral infarction

OBJECTIVE

To observe the curative effect of dl-3-n-Butylphthalide (NBP) on patients with acute cerebral infarction (ACI) and its effects on levels of serum vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF).

PATIENTS AND METHODS

A total of 160 ACI patients treated in our hospital who met the criteria were selected and randomly divided into treatment group (n=80, including 42 males and 38 females) and control group (n=80, including 40 males and 40 females). The control group was treated with routine drug therapy, while the treatment group was treated with butylphthalide on this basis. The curative effect was evaluated using the National Institute of Health Stroke Scale (NIHSS) and the Activity of Daily Life Scale (ADL Scale). The levels of the two factors in serum were measured using enzyme-linked immunosorbent assay (ELISA), and the changes in the levels of the two factors in serum at different time points before and after treatment were compared between the two groups.

RESULTS

After treatment, the levels of the two factors in serum in both groups were significantly increased compared with those before treatment (p<0.05), and the increase in treatment group was more significant than that in control group (p<0.05). The scores of ADL scale in both groups were significantly increased after treatment compared with those before treatment, and the increase in treatment group was more significant than that in control group (p<0.05). The scores of NIHSS in both groups were significantly decreased compared with those before treatment, and the decrease in treatment group was more significant than that in control group (p<0.05).

CONCLUSIONS

NBP can improve the expressions of VEGF and bFGF in serum of ACI patients, and its effect is superior to that of conventional drugs.

Laparoscopic abdominoperineal excision with trans-abdominal individualized levator transection: interim analysis of a randomized controlled trial

AIM

Extralevator abdominoperineal excision (ELAPR) is challenging 'conventional' abdominoperineal excision (APR), yet the safety and efficacy of ELAPR is still under debate. We therefore developed a laparoscopic APR with trans-abdominal individualized levator transection (LAPR-TILT) approach and compared the outcome with a conventional laparoscopic APR (CLAPR).

METHOD

All eligible patients were entered a single-centre randomized controlled trial to compare CLAPR and LAPR-TILT. We assessed the first 185 patients, including operative findings, complications, histopathology and urogenital function.

RESULTS

Ninety-three patients in the CLAPR group and 92 patients in the APR-TILT group were included for analysis. The APR-TILT procedure took less time [137 (101-175) min vs 146 (102-187) min; P = 0.03], mainly owing to faster perineal dissection. APR-TILT resulted in a reduced rate of bowel perforation (1.1% vs 8.6%; P = 0.04), circumferential resection margin positivity (1.1% vs 10.8%; P = 0.01) and postoperative wound complications (5.4% vs 16.2%; P = 0.02) compared with the CLAPR procedure. At a median follow-up of 19 months after surgery, three patients (3.2%) in the CLAPR group had tumour recurrence while no tumour recurrence occurred in the LAPR-TILT group. Patients who underwent LAPR-TILT reported fewer urinary or sexual problems (LAPR-TILT vs CLAPR, 10.9% vs 24.7% and 17.4% vs 38.7%, respectively).

CONCLUSION

Compared with CLAPR, LAPR-TILT achieved better pathological results for factors that are surrogate parameters for local recurrence. LAPR-TILT could also reduce the risk of urogenital dysfunction.

Experimental quantum-walk revival with a time-dependent coin

We demonstrate a quantum walk with time-dependent coin bias. With this technique we realize an experimental single-photon one-dimensional quantum walk with a linearly ramped time-dependent coin flip operation and thereby demonstrate two periodic revivals of the walker distribution. In our beam-displacer interferometer, the walk corresponds to movement between discretely separated transverse modes of the field serving as lattice sites, and the time-dependent coin flip is effected by implementing a different angle between the optical axis of half-wave plate and the light propagation at each step. Each of the quantum-walk steps required to realize a revival comprises two sequential orthogonal coin-flip operators, with one coin having constant bias and the other coin having a time-dependent ramped coin bias, followed by a conditional translation of the walker.

Osteoblast proliferation is enhanced upon the insulin receptor substrate 1 overexpression via PI3K signaling leading to down-regulation of NFκB and BAX pathway

The insulin receptor substrate 1 (IRS1) promotes bone formation via osteoblast proliferation mediated by PI3K/Akt signaling. A reduction in NFκB activity in osteoblasts results in an increase in bone formation. The NFκB signaling pathway leads to increased expression of BAX, which contributes to osteoblast apoptosis. The purpose of this study was to investigate the expression of recombinant plasmid enhanced green fluorescent protein-N1 (pEGFP-N1) that transferred IRS1 gene into osteoblasts in vitro and evaluate the effects of IRS1 overexpression on NFκBp65 and on BAX. Osteoblasts were transfected with pEGFP-N1 or pEGFP-N1 encoding wild-type IRS1 (pEGFP-N1-IRS1). Cell cycle analysis was performed using flow cytometry. The expression levels of NFκBp65 and BAX were measured by Western blotting. Our results revealed that overexpression of IRS1 stimulated osteoblast proliferation, as evidenced by an increase in the number of cells in the S phase compared to controls. IRS1 overexpression in osteoblasts activated the PI3K/Akt pathway, and inhibited expression of NFκBp65 and BAX. When osteoblasts transfected with pEGFP-N1-IRS1 were exposed to a PI3K inhibitor (LY294002), the effects of IRS1 overexpression were reversed. On the basis of our study, it seems that osteoblasts proliferated upon IRS1 overexpression due to inhibition of the NFκB pathway and downregulation of BAX through PI3K/Akt signaling.

The role of IVS14+1 G > A genotype detection in the dihydropyrimidine dehydrogenase gene and pharmacokinetic monitoring of 5-fluorouracil in the individualized adjustment of 5-fluorouracil for patients with local advanced and metastatic colorectal cancer: a preliminary report

AIM

We retrospectively investigated the relationship between IVS14+1 G > A genotype of the dihydropyrimidine dehydrogenase (DPD) gene with plasma concentration of 5-fluorouracil (5-FU) as well as adverse reactions in 80 patients with locally advanced or metastatic colorectal cancer.

PATIENTS AND METHODS

Eighty patients with un-resectable locally advanced or metastatic colorectal cancer were treated with Folfox-6 regimen, which repeated every two weeks for at least three cycles. Single nucleotide polymorphisms for DPD gene were analyzed before chemotherapy by high-resolution melting (HRM) analysis. The plasma concentration of fluorouracil was measured by high performance liquid chromatography (HPLC) after continuous infusion of fluorouracil over 12 h in each cycle. The average values of plasma concentrations in each cycle were calculated, and the factors related to plasma concentration of 5-FU were screened by stepwise regression.

RESULTS

All patients were divided into three groups according to the predictive confidence interval of plasma concentration of 5-FU, and the average plasma concentrations of fluorouracil in each cycle of these three groups were less than or equal to 26.83 mg/L, 26.83-40.62 mg/L, and more than 40.62 mg/L, respectively. Stepwise regression analysis showed that the plasma concentration of fluorouracil was associated with myelosuppression, hand-foot syndrome, diarrhea, overall survival (OS) and DPD genotype. In efficacy, the median progression-free survival PFS (mPFS) and OS (mOS) of group 2 and group 3 were both significantly higher than those of group 1.

CONCLUSIONS

Among the advanced colorectal cancer patients receiving fluorouracil-based chemotherapy, those with plasma concentration of 5-FU above 26.83 mg/L can obtain better survival; for patients with heterozygous DPD IVS14+1 mutation, 5-FU dose should be appropriately reduced according to last plasma concentration to reduce adverse reactions, while the homozygous ones should avoid application of 5-FU and its derivatives.

Studies on the Effect of Pellet Size on Positive Conveying in Helically Grooved Single Screw Extruders

The helical grooved barrel feed section permits, when the barrel channel aspect ratio and the barrel channel helical angle are properly designed, an operating mode where the positive conveying is prevailing. While the pellet size of materials is varied, different dimension relationships of the barrel channel depth and pellet size could induce different equivalent barrel channel aspect ratios with the transformation of solids conveying mechanisms from the positive conveying to the friction-drag conveying. Considering the effect of dimension relationships on the solids conveying mechanism, a novel pellet-size physical model was established to guide the available design of the barrel channel geometry for positive conveying. In the pellet-size model, one or two shear interfaces were identified inside the solid-plug resulting in different equivalent barrel channel aspect ratios, based on which the solids conveying mechanism on the shear interfaces was detailed by the boundary condition equations for positive conveying. Besides, the theoretical simulations are also compared with the on-line measuring experimental data. The results show that the equivalent barrel channel aspect ratio on the shear interfaces exists indeed and determines the solids conveying mechanism, which is well confirmed by the excellent consistence between the predicted and measured data.

miR-155* mediates suppressive effect of PTEN 3'-untranslated region on AP-1/NF-κB pathway in HTR-8/SVneo cells

Among miRNAs, miR-155 is a known regulator of immune system. Accumulating studies have revealed the connections between miR-155 and activator protein 1 (AP-1)/nuclear factor (NF)-κB. However, miR-155*, a miR-155 paralog, has so far been less studied. Here we demonstrated that miR-155*, induced by lipopolysaccharide (LPS) in an AP-1/NF-κB dependent manner, played a positive feedback role in AP-1/NF-κB pathway via targeting interleukin-1 receptor-associated kinase M (IRAKM) and NF-κB inhibitor interacting Ras-like 1 (NKIRAS1) in trophoblasts. Our study further proved that miR-155*-targeted PTEN 3'-untranslated region (3'UTR) increased IRAKM and NKIRAS1 expression by competing for miR-155* binding, thereby suppressing AP-1/NF-κB activation induced by LPS.

Modeling of Melt Conveying in a Novel Screw-Nested Extruder

A novel screw-nested extruder is fabricated, which consists of double extrusion systems. The inner screw couples with one inner barrel, whose outer configuration acts as the screw for the outer barrel. The nested screw extrusion systems can co-extrude when the inner barrel/outer screw rotates. Each extrusion system can also work independently as one general extruder. A new mathematical model of an isothermal Newtonian flow is developed to describe the melt flow in the extruder. The analytical solutions of flow rate are well in agreement with the Campbell's experimental data for screw drag flow, screw flight displacement flow and barrel drag flow when the boundary conditions are obtained for the special cases in which the screw core, screw flight and the barrel rotate independently or in pairs. This can not be explained by conventional parallel-plate models. Further, the model is also well used to analyze the melt flow in the inner extrusion system of the novel nested screw extruder.

A galactose-specific sugar: phosphotransferase permease is prevalent in the non-core genome of Streptococcus mutans

Three genes predicted to encode the A, B and C domains of a sugar : phosphotransferase system (PTS) permease specific for galactose\(EII(Gal) ) were identified in the genomes of 35 of 57 recently sequenced isolates of Streptococcus mutans, the primary etiological agent of human dental caries. Mutants defective in the EII(Gal) complex were constructed in six of the isolates and showed markedly reduced growth rates on galactose-based medium relative to the parental strains. An EII(Gal) -deficient strain constructed using the invasive serotype f strain OMZ175 (OMZ/IIGal) expressed significantly lower PTS activity when galactose was present as the substrate. Galactose was shown to be an effective inducer of catabolite repression in OMZ175, but not in the EII(Gal) -deficient strain. In a mixed-species competition assay with galactose as the sole carbohydrate source, OMZ/IIGal was less effective than the parental strain at competing with the oral commensal bacterium Streptococcus gordonii, which has a high-affinity galactose transporter. Hence, a significant proportion of S. mutans strains encode a galactose PTS permease that could enhance the ability of these isolates to compete more effectively with commensal streptococci for galactose in salivary constituents and the diet.

Generation of polarization-entangled photon pairs via concurrent spontaneous parametric downconversions in a single χ(2) nonlinear photonic crystal

We propose a scheme for generating polarization-entangled photon pairs using a χ((2)) nonlinear photonic crystal, which is designed for enabling two concurrent quasi-phase-matched spontaneous parametric downconversion processes. Beamlike photon pairs produced from each process are collinear but noncollinear with the pump. Moreover, the source we design works in a postselection-free way and applies to both degenerate and nondegenerate cases. Combining possible waveguide technologies, our scheme may provide an integrated polarization entanglement source.

MicroRNA-155 inhibits proliferation and migration of human extravillous trophoblast derived HTR-8/SVneo cells via down-regulating cyclin D1

MiR-155 is known to participate in various cellular processes by targeting gene expression. We previously revealed a link between miR-155 and perturbation of trophoblast invasion and differentiation. This study aimed to investigate the target molecule(s) of miR-155 on the influence on the proliferation and migration of trophoblast cells. Bioinformatics analysis showed that, at the 3' untranslated region (UTR) of cyclin D1, six bases are complementary to the seed region of miR-155. Luciferase assays and cyclin D1 3'UTR transfection assays validated that cyclin D1 3'UTR was the target of miR-155 in HTR-8/SVneo cells. Overexpression of miR-155 in HTR-8/SVneo cells reduced the level of cyclin D1 protein, decreased cell proliferation and invasion, and increased cell number at the G1 stage. Furthermore, the increased expression of miR-155 also regulated the protein levels of kinase inhibitory protein p27 and phosphorylated cytoskeletal protein filamin A. In conclusion, we found that cyclin D1 may be a target of miR-155 in HTR-8/SVneo cells, and demonstrated a negative regulatory role of miR-155 involved in cyclin D1/p27 pathway in proliferation and migration of the cells.

Identification of genes preferentially expressed in goat hair follicle anagen-catagen transition using suppression subtractive hybridization

Suppressive subtraction hybridization (SSH) was used to identify differentially expressed genes in goat (Capra hircus) hair follicle anagen-catagen transition. The cDNA fragments, derived from SSH positive subtractive library (tester: anagen-catagen transition, driver: later anagen), were cloned into pEGM-T vector. Two hundred cDNA fragments screened from this library were subjected to identify forty-five unregulated isolates. Sequence analysis revealed that these fragments represented twenty-three genes. Blasting analysis with database in GenBank showed that twenty genes were previously clearly annotated, two were homologous to un-annotated expressed sequence tag (ESTs), and one might be novel. To identify characters of gene expression, seven genes in later anagen and anagen-catagen transition skin tissues were chosen for quantitative real-time PCR. Results indicated that expression of these seven genes varied much, reaching threefold among them, furthering indicating that expression of those genes was up-regulation in the anagen-catagen transition. We characterized expression levels of this potential novel gene and the goat ectodysplasin A during differential stages of hair cycle. These profiles suggested that these two genes might play a role in the goat secondary hair follicle cycle.

Short-term administration of ACTH improves plasma lipid profile and renal function in kidney transplant patients

The present study investigated effects of short-term administration of adrenocorticotrophic hormone (ACTH) on blood lipid profile and renal function in kidney transplant patients. Six patients who had kidney transplantations 2 to 10 years earlier received ACTH intramuscularly (1 mg/d) for 4 days. We analyzed serum levels of lipids, lipoproteins, apolipoproteins, blood creatinine, and other parameters. Short-term ACTH treatment significantly decreased serum apolipoprotein B and apolipoprotein AI, whereas it significantly increased plasma high-density lipoproteins (HDL). Interestingly, creatinine level moderately decreased and creatinine clearances moderately increased among five of six patients. Hepatic function and serum concentration of cyclosporine did not change. There were no serious side effects during ACTH treatment. It was concluded that ACTH treatment had beneficial effects on serum lipoprotein profile, potentially improving renal function in kidney transplant patients. Further observations are needed to confirm these effects.

Management of pediatric radiation dose using GE's Revolution digital radiography systems

Digital flat-panel x-ray detectors offer excellent image quality and dose efficiency in addition to clinical productivity, connectivity, and adaptability to advanced clinical applications. GE's Revolution systems provide two modes of exposure control for setting the dose operating point, fixed time and automatic exposure control, the latter of which maintains high image signal-to-noise ratio for the given technique settings. In addition to enhancing detail contrast and compressing the dynamic range, postprocessing automatically determines the best window level and width for display, taking into account the dose at which the image was acquired. Several studies have examined the reduction in patient dose achievable with Revolution systems as compared to competing technologies, and results indicate significant dose savings with equivalent or superior image quality. For pediatric exams, pediatric default techniques provide for a lower patient dose as compared to adult techniques. Therefore, GE's Revolution systems can achieve a high image quality-to-dose ratio for pediatric imaging using the combined advantages of dose-efficient detection, advanced postprocessing, and independently adjustable pediatric techniques.

[Influence of a triplex superimposed treatment on HBV replication and mutation during treating chronic hepatitis B]

OBJECTIVE

To observe and evaluate the influence of a new antiviral treatment scheme on HBV replication and mutation during treating chronic hepatitis B.

METHODS

In the test group, lamivudine, IFN alpha-2b, Astragalus membranaceus were chosen as a triplex superimposed treatment scheme for treating the patients who were on the state of HBV high replication and involved in the clinical condition of chronic hepatitis B. The control group was treated with lamivudine alone. The observed parameters percentage of patients in whom HBV DNA became undetectable (serum HBV DNA<1.6 ng/L), HBeAg/anti-HBe seroconversion rate; HBV DNA serum level; HBV YMDD mutation rate and pre-C region mutation rate.

RESULTS

Compared with that of the control group, HBV DNA undetectable rate of the test group increased markedly at weeks 12, 36, 48(P <0.05), HBeAg negative rate of the group increased markedly at week 36, 48(P <0.05), while anti-HBe positive rate increased only at week 48 (31.58 vs.19.23%, P <0.05). After 4 weeks of treatment, HBV DNA serum level of both the test group and the control group reduced very remarkably (P <0.01), and at week 48, reduced more significantly (P <0.001). Compared with the control group, HBV DNA serum level of the test group reduced notably at week 12 (P <0.05) and very notable at week 36 and 48(P <0.01). At week 12, the pre-C region mutation occurred in the test group, and at week 24, 36,48, the pre-C region and YMDD mutations occurred in both the test group and the control group.

CONCLUSIONS

As to anti-viral treatment of chronic hepatitis B, the triplex superimposed treatment had better efficacy than lamivudine alone.

How to optimize OCT image

Quantization, which maps real values of raw data to a series of fixed gray levels, is an inevitable step in Optical Coherence Tomography (OCT) image formation. Three new quantization methods, Minimum Distortion, Information Expansion and Maximum Entropy are applied in the specific problem. Quantization results of a capillary with milk and the femoralis of rabbit are shown in this paper. Comparisons with the present log-based methods show that a suitable quantization method significantly increases contrast, SNR and visual fineness of the final image and reduces quantization error effectively. Applicability of different quantization methods is also discussed.

Study of the electrochemical behavior of mitoxantrone and its determination at a Co-C modified ultramicroelectrode

In 0.005 mol dm-3 Tris-0.05 mol dm-3 NaCl buffer solution (pH 7.10), the electrochemical behavior of mitoxantrone was studied by linear-sweep voltammetry and cyclic voltammetry at a Co-carbon fiber ion implantation modified ultramicroelectrode. A sensitive reduction peak was obtained. The peak potential was -0.798 V (vs. SCE), the peak current was proportional to the concentration of mitoxantrone over the range of 2.0 x 10(-7)-6.0 x 10(6) mol dm-3 and the detection limit was 4.2 x 10(-8) mol dm-3. This method was applied to the direct determination of mitoxantrone in urine. Recoveries were in the range 95.4-105.8%. The reduction process was quasi-reversible with absorptive characteristics at a Co-C ultramicroelectrode. According to Laviron's theory, the electrode reaction rate constant ks and the electron transfer alpha of mitoxantrone were 4.4 s-1 and 0.48, respectively. The composition and depth distribution of elements on the surface of the Co-C ultramicroelectrode were determined by Auger electron spectroscopy. The experiments showed that Co was implanted into the surface of the carbon fiber, and the Co-C ultramicroelectrode had good stability and reproducibility.

Dose efficiency and low-contrast detectability of an amorphous silicon x-ray detector for digital radiography

The effect of dose reduction on low-contrast detectability is investigated theoretically and experimentally for a production grade amorphous silicon (a-Si) x-ray detector and compared with a standard thoracic screen-film combination. A non-prewhitening matched filter observer model modified to include a spatial response function and internal noise for the human visual system (HVS) is used to calculate a signal-to-noise ratio (SNR) related to object detectability. Other inputs to the SNR calculation are the detective quantum efficiency (DQE) and the modulation transfer function (MTF) of the imaging system. Besides threshold detectability, the model predicts the equivalent perception dose ratio (EPDR), which is the fraction of the screen film exposure for which the digital detector provides equal detectability. Images of a contrast-detail phantom are obtained with the digital detector at dose levels corresponding to 27%, 41%, 63% and 100% of the dose used for screen-film. The images are used in a four-alternative forced choice (4-AFC) observer perception study in order to measure threshold detectability. A statistically significant improvement in contrast detectability is measured with the digital detector at 100% and 63% of the screen-film dose. There is no statistical difference between screen-film and digital at 41% of the dose. On average, the experimental EPDR is 44%, which agrees well with the model prediction of 40%.