Towards continuous-to-continuous 3D imaging in the real world

Imaging systems are often modeled as continuous-to-discrete mappings that map the object (i.e. a function of continuous variables such as space, time, energy, wavelength, etc) to a finite set of measurements. When it comes to reconstruction, some discretized version of the object is almost always assumed, leading to a discrete-to-discrete representation of the imaging system. In this paper, we discuss a method for single-photon emission computed tomography (SPECT) imaging that avoids discrete representations of the object or the imaging system, thus allowing reconstruction on an arbitrarily fine set of points.

Hormone replacement therapies, oral contraceptives, reproductive factors and colorectal adenoma risk: a systematic review and dose-response meta-analysis of observational studies

AIM

The association between the use of oral contraceptives and hormone replacement therapy (HRT) or other reproductive factors and the risk of colorectal adenoma (CRA) remains controversial. Our study aimed to review the evidence by conducting a dose-response meta-analysis to investigate this association.

METHODS

We searched PubMed and Embase databases for relevant studies published until May 2017. Traditional and dose-response meta-analyses were conducted. Sensitivity analysis was performed to evaluate the robustness of the results. Cumulative meta-analysis was used to assess the risk of different oral contraceptive formulations or generations.

RESULTS

A total of 19 observational studies, with 21 923 CRA cases and 1 030 711 participants, were included in the meta-analysis. Ever HRT use showed a potential inverse association with CRA risk [relative risk (RR) 0.83, 95% CI 0.70-1.00]. The dose-response meta-analysis further demonstrated that HRT use could reduce CRA risk. Compared with no HRT use, the predicted RRs were 0.82 (95% CI 0.67-0.99), 0.76 (95% CI 0.59-0.98) and 0.77 (95% CI 0.62-0.96) for 3, 6 and 9 years of HRT use, respectively. All other factors were not statistically significantly associated with CRA risk.

CONCLUSIONS

This study indicated that only HRT use might reduce the risk of developing CRA. Any advice regarding HRT use to prevent CRA should be tailored to the individual risks and potential benefits. Large, well-designed prospective studies with long-term follow-up are required to further clarify the aetiology of CRA.

Intermittent lead-induced stress on antioxidant enzyme activity and subcellular distribution of Pb in Pogonatherum crinitum seedlings

Pogonatherum crinitum is a promising lead (Pb) hyperaccumulator due to its high Pb tolerance and accumulation ability. However, the mechanisms that support Pb accumulation and tolerance in P. crinitum are not yet clearly understood. An indoor hydroponic experiment was conducted by cultivating P. crinitum seedlings exposed to intermittent Pb stress for 60 days, divided into four stages (T1, T2, T3 and T4), with a 15-day duration per stage. The following concentrations of Pb were used: 0, 500, 0, 500 mg·l^-1 and 0, 1000, 0, 1000 mg·l^-1 ). Antioxidant enzyme activity, Pb concentration and subcellular distribution of Pb were measured at each of the above stages. The results showed that superoxide dismutase (SOD) activity in shoots, and SOD, peroxidase (POD) and malondialdehyde (MDA) activity in shoots and roots significantly increased from T1 (no Pb stress) to T2 (Pb stress) in both 500 mg·l^-1 and 1000 mg·l^-1 treatments; however, no significant difference was noted between stages T3 (no Pb stress) and T4 (Pb stress). There was no obvious effect of Pb stress on catalase (CAT) activity in shoots and roots among different stages. The Pb concentration in shoots was up to 5090.90 mg·kg^-1 and 7573.57 mg·kg^-1 , and the bioconcentration factor (BFC) was 10.18 and 7.57 for the 500 mg·l^-1 and 1000 mg·l^-1 treatments, respectively, which confirmed the Pb hyperaccumulator characteristics of P. crinitum. For plants under Pb stress, most of the Pb was fixed in the cell walls, with a smaller amount in leaves and root vacuoles. Both SOD and POD scavenging of reactive oxygen radicals and fixing and compartmentalisation of Pb in the cell wall might play important roles in detoxification of P. crinitum seedlings in response to Pb stress. There was no phased response of P. crinitum to intermittent Pb stress and the physiological response to Pb stress may be contiguous.

Atomic view into Plasmodium actin polymerization, ATP hydrolysis, and fragmentation

Plasmodium actins form very short filaments and have a noncanonical link between ATP hydrolysis and polymerization. Long filaments are detrimental to the parasites, but the structural factors constraining Plasmodium microfilament lengths have remained unknown. Using high-resolution crystallography, we show that magnesium binding causes a slight flattening of the Plasmodium actin I monomer, and subsequent phosphate release results in a more twisted conformation. Thus, the Mg-bound monomer is closer in conformation to filamentous (F) actin than the Ca form, and this likely facilitates polymerization. A coordinated potassium ion resides in the active site during hydrolysis and leaves together with the phosphate, a process governed by the position of the Arg178/Asp180-containing A loop. Asp180 interacts with either Lys270 or His74, depending on the protonation state of the histidine, while Arg178 links the inner and outer domains (ID and OD) of the actin protomer. Hence, the A loop acts as a switch between stable and unstable filament conformations, the latter leading to fragmentation. Our data provide a comprehensive model for polymerization, ATP hydrolysis and phosphate release, and fragmentation of parasite microfilaments. Similar mechanisms may well exist in canonical actins, although fragmentation is much less favorable due to several subtle sequence differences as well as the methylation of His73, which is absent on the corresponding His74 in Plasmodium actin I.

A detailed mechanistic study of malaria parasite actins reveals at the atomic level how they polymerize, hydrolyze ATP, and are fragmented to keep actin filament lengths short enough for parasite survival.

Chinese Mongolian horses may retain early domestic male genetic lineages yet to be discovered

The Mongolian horse represents one of the most ancient extant horse populations. In this study we determined the male-specific region of the Y chromosome (MSY) haplotype distribution in 60 Chinese Mongolian horses representing five distinct populations. Cosmopolitan male lineages were predominant in horses from one improved (Sanhe), one Chinese Mongolian subtype (Baicha Iron Hoof) and one indigenous (Abaga Black) population. In contrast, autochthonous Y chromosome diversity was evident among the two landrace populations (Wushen and Wuzhumuqin), as the majority of their MSY haplotypes were situated at root nodes in a network. Our results also suggest gene flow between Chinese Mongolian and Arabian horses, as an appreciable number of Wuzhumuqin horses carried haplotypes that are typically observed in Arabian horses. Although most horses carried modern haplotypes as a direct result of recent breed improvement, authentic Chinese Mongolian horses retain an ancient signature of paternal lineages that has not previously been described in extant horse populations. Therefore, further characterization of MSY variation in these populations will be important for the discovery of lost diversity in modern domestic horses and also for understanding the evolutionary history of equine paternal lineages.

[Clinical outcome of postchemotherapy retroperitoneal lymph node dissection and predicting retroperitoneal histology in advanced nonseminomatous germ cell tumours of the testis]

Objective: To explore the clinical outcome of advanced testicular nonseminomatous germ cell cancer patients undergoing post chemotherapy retroperitoneal lymph node dissection (PC-RPLND), and to analyze the relevant prognostic factors of lymph node pathological. Methods: A total of 43 consecutive testicular nonseminomatous germ cell cancer patients underwent PC-RPLND between March 2001 and December 2014 in Department of Urology at Sun Yat-sen University Cancer Center were retrospectively reviewed. The average age of the patients was (29.0±11.5) years (ranging from 12 to 58 years). Before PC-RPLND, 22 patients were classified as phase Ⅱ, while 21 were phase Ⅲ. Primary tumor histology revealed seminomatous elements in 19 cases, embryonal cell carcinoma in 22 cases, yolk sac tumor in 13 cases, chorionic carcinoma in 3 cases, mature teratomatous elements in 11 and immature teratomatous elements in 2 cases. Patients were treated with cisplatin-based chemotherapy after orchectomy and then underwent surgical resection of retroperitoneal lymph nodes.After PC-RPLND, all patients underwent a periodic review including the blood routine, biochemistry routine and computed tomography or ultrasonograph of the chest, the abdomen and the pelvis. The association of pathological data with patient's clinic features and the correlations between molecular features detected with each other were assessed by the t test, χ(2) and Fisher's exact test. Multivariate logistic regression were used to assess prognostic factors. Results: The median operative time was 278 minutes (ranging from 50 to 715 minutes). Median blood loss was 425 ml (ranging from 50 to 5 000 ml). Eight patients received blood transfusion intra-operatively, 2 patients underwent adjunctive surgical procedures, 4 patients developed ileus and 4 had an ascites chylosus following PC-RPLND, 1 patient had a postoperative hyperthermia and retrograde ejaculation was present in 10 patients. The transverse diameter of the residual tumor in patients ranged from 0.8 to 18.2 cm. Necrosis, teratoma and viable germ cell tumors were found in 15, 17 and 11 of all patients. The median follow-up time was 46 months (ranging from 6 to 169 months). There were 39 patients had no tumor recurrence, 7 patients were found recurrence after PC-RPLND, 5 died of malignant germ cell tumor. The normal serum lactate dehydrogenase (LDH) level before chemotherapy (HR=25.811, 95%CI: 0.678 to 982.624, P=0.017) and relative changes more than 50% in retroperitoneal lymph node size (HR=0.016, 95%CI: 0 to 0.698, P=0.032) were statistically significant prognostic factors of the presence of necrosis. Conclusions: Since most residual masses are not sensitive to chemotherapy, PC-RPLND is still an essential part of the treatment of metastatic testicular nonseminomatous germ cell cancer. Patients with the normal serum LDH level before chemotherapy and a shrinkage of 50% or more in retroperitoneal mass have a considerably chance of having necrosis in the retroperitoneum resection. This may help to refine the selection of candidates for PC-RPLND.

Abstract OT3-03-01: Open-label, single-arm study evaluating the antitumor activity and safety of niraparib as neoadjuvant treatment in patients with localized, HER2-negative, BRCA-mutant breast cancer

Background: Neoadjuvant chemotherapy is administered to patients with operable breast cancer to downstage the tumor to allow for less extensive surgery and to provide prognostic information about drug efficacy and risk of disease recurrence. Patients who achieve a pathological complete response (pCR) following neoadjuvant treatment have a more favorable outcome than patients with residual invasive disease. Single-agent poly(ADP-ribose) polymerase (PARP) inhibitors have clinical efficacy in BRCA-mutated breast cancer. Niraparib, a potent and selective PARP1/2 inhibitor, is approved for maintenance treatment of patients with recurrent ovarian cancer and has demonstrated strong antitumor activity in in vivo studies with BRCA1-mutant breast cancer. The objective of this study is to evaluate the antitumor activity of single-agent niraparib in the neoadjuvant treatment of patients with localized, human epidermal growth factor receptor 2 (HER2)-negative, BRCAmut breast cancer.

Trial Design: This is an open-label, single-arm pilot study with a target enrollment of 20 evaluable patients. Eligible patients are those ≥18 years old with histologically-confirmed HER2-negative localized breast cancer and either a BRCA1 or BRCA2 mutation (germline or somatic) and no prior anti-cancer therapies for the current malignancy. Patients will receive 200 mg of oral niraparib once daily for 2 months, after which they may either proceed directly to surgery or receive chemotherapy at the discretion of the physician. The primary endpoint is tumor response rate based on the change in tumor volume as measured by breast MRI after 2 months of treatment with niraparib; a response is defined as ≥30% reduction of tumor volume from baseline. Secondary endpoints include pCR rate, tumor response rate based on the change in tumor volume as measured by breast ultrasound, and safety and tolerability. Data will be summarized in a descriptive nature by frequency distributions (number and percentage of patients) for categorical variables and by the mean, median, and standard deviation for continuous variables. Tumor response rate will be tabulated together with its 95% binomial exact confidence interval.

Funding: TESARO, Inc., Waltham, MA, USA sponsored the study.

Citation Format: Han H, Hamilton E, Irie H, Isakoff S, Jelovac D, Liem A, Liu MC, Milillo A, Nangia J, Page D, Reeves J, Santa-Maria C, Duncan M, Graham JR, Chen J, Dezube BJ, Spring L. Open-label, single-arm study evaluating the antitumor activity and safety of niraparib as neoadjuvant treatment in patients with localized, HER2-negative, BRCA-mutant breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT3-03-01.

Abstract P1-15-02: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Schwab R, Clark A, Yau C, Wolf D, Chien AJ, Majure M, Ewing C, Wallace A, Roesch E, Helsten T, Forero A, Stringer-Reasor E, Vaklavas C, Nanda R, Jaskowiak N, Boughey J, Haddad T, Han H, Lee C, Albain K, Isaacs C, Elias A, Ellis E, Shah P, Lang J, Lu J, Tripathy D, Kemmer K, Yee D, Haley B, Korde L, Edmiston K, Northfelt D, Viscusi R, Khan Q, I-SPY 2 Consortium, Symmans WF, Perlmutter J, Hylton N, Rugo H, Melisko M, Wilson A, Singhrao R, Asare S, van't Veer L, DeMichele A, Berry D, Esserman L. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-15-02.

Molecular structure and function of myelin protein P0 in membrane stacking

Compact myelin forms the basis of nerve insulation essential for higher vertebrates. Dozens of myelin membrane bilayers undergo tight stacking, and in the peripheral nervous system, this is partially enabled by myelin protein zero (P0). Consisting of an immunoglobulin (Ig)-like extracellular domain, a single transmembrane helix, and a cytoplasmic extension (P0ct), P0 harbours an important task in ensuring the integrity of compact myelin in the extracellular compartment, referred to as the intraperiod line. Several disease mutations resulting in peripheral neuropathies have been identified for P0, reflecting its physiological importance, but the arrangement of P0 within the myelin ultrastructure remains obscure. We performed a biophysical characterization of recombinant P0ct. P0ct contributes to the binding affinity between apposed cytoplasmic myelin membrane leaflets, which not only results in changes of the bilayer properties, but also potentially involves the arrangement of the Ig-like domains in a manner that stabilizes the intraperiod line. Transmission electron cryomicroscopy of native full-length P0 showed that P0 stacks lipid membranes by forming antiparallel dimers between the extracellular Ig-like domains. The zipper-like arrangement of the P0 extracellular domains between two membranes explains the double structure of the myelin intraperiod line. Our results contribute to the understanding of PNS myelin, the role of P0 therein, and the underlying molecular foundation of compact myelin stability in health and disease.

Evaluation of coagulation disorders by thromboelastography in children with systemic lupus erythematosus

Background

The coagulation status of patients with systemic lupus erythematosus (SLE) is quite complicated, and there are currently no simple efficient methods for its evaluation. We explored the feasibility of thromboelastography (TEG) for this purpose.

Methods

Paediatric SLE patients were divided into different groups based on Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) scores. TEG parameters were compared between patients and healthy controls (HCs) and in patients by level of disease activity. Six patients treated with pulse methylprednisolone were also analysed before and after treatment.

Results

Thirty-nine children with SLE were enrolled, one of whom had bleeding and three of whom had thrombosis. The four TEG tracings of these four children were different. The TEG parameters of the patients (except the four children mentioned above) showed hypercoagulability, shortened R and K times, increased α-angle and maximum amplitude (MA), decreased LY30 and increased clot index (CI) compared with the parameters of the HCs ( P < 0.05). With respect to disease activity, patients with higher SLEDAI scores showed more obvious hypercoagulability with shortened R and K times and increased α-angle and CI ( P < 0.05). Furthermore, there was a negative correlation between both the R time and K time and SLEDAI scores ( r = –0.435, P < 0.01 and r  =  –0.572, P  < 0.001, respectively) and a positive correlation between both α-angle and CI and SLEDAI scores ( r = 0.581, P  < 0.001 and r  =  0.544, P  < 0.01, respectively). No significant difference in coagulation status was found between pre- and post-pulse therapy.

Conclusions

Compared with the HCs, paediatric SLE patients showed hypercoagulability caused by increased coagulation and decreased fibrinolysis. These coagulation changes were associated with disease activity. TEG could be a potential tool for evaluating the coagulation status of children with SLE.