Hit Event Research Articles

Performance of the MALTA telescope

MALTA is part of the Depleted Monolithic Active Pixel sensors designed in Tower 180 nm CMOS imaging technology. A custom telescope with six MALTA planes has been developed for test beam campaigns at SPS, CERN, with the ability to host several devices under test. The telescope system has a dedicated custom readout, online monitoring integrated into DAQ with realtime hit map, time distribution and event hit multiplicity. It hosts a dedicated fully configurable trigger system enabling to trigger on coincidence between telescope planes and timing reference from a scintillator. The excellent time resolution performance allows for fast track reconstruction, due to the possibility to retain a low hit multiplicity per event which reduces the combinatorics. This paper reviews the architecture of the system and its performance during the 2021 and 2022 test beam campaign at the SPS North Area.

Analysis of Acoustic Emission Signals Processed with Wavelet Transform for Structural Damage Detection in Concrete Beams

Concrete beams are elements used in many civil structures; unfortunately, they can contain cracks that lead to the collapse of the structures if those defects are not detected early enough. In this article, a new method to determine the structural condition of concrete beams subjected to bending is proposed. In general, it is based on the processing of the acoustic emissions (AE) signals, which are generated during the application of a load, by using the mathematical tool called wavelet transform (WT). The sound of the internal energy/crack is recorded as a hit or AE signal event; then, those signals acquired as waveforms are post-processed with the continuous WT (CWT); then, the wavelet energy (WE) is calculated for each hit by using an adequate scale range and the most convenient mother wavelet. Thus, with this method, it is possible to determine the structural condition (healthy or damaged) of concrete beams subjected to bending just by calculating the WE of any hit at any time and, even more, it is possible to define more precisely the stage of the structural condition as a healthy condition, micro-cracks appearance, the manifestation of a principal crack (hit with the highest WE), propagation of the principal crack, and final rupture. This method is experimentally validated in the laboratory, and additionally, ultrasonic pulse velocity tests (UPVT) are performed for some specimens to confirm the change between healthy and damaged conditions. The results are promising in order to apply this effective method in concrete beams of real-life structures.

Low-energy X-ray performance of SOI pixel sensors for astronomy, “XRPIX”

We have been developing a new type of X-ray pixel sensors, “XRPIX”, allowing us to perform imaging spectroscopy in the wide energy band of 1–20keV for the future Japanese X-ray satellite “FORCE”. The XRPIX devices are fabricated with complementary metal-oxide-semiconductor silicon-on-insulator technology, and have the “Event-Driven readout mode”, in which only a hit event is read out by using hit information from a trigger output function equipped with each pixel. This paper reports on the low-energy X-ray performance of the “XRPIX6E” device with a Pinned Depleted Diode (PDD) structure. The PDD structure especially reduces the readout noise, and hence is expected to largely improve the quantum efficiencies for low-energy X-rays. While F-K X-rays at 0.68keV and Al-K X-rays at 1.5keV are successfully detected in the “Frame readout mode”, in which all pixels are read out serially without using the trigger output function, the device is able to detect Al-K X-rays, but not F-K X-rays in the Event-Driven readout mode. Non-uniformity is observed in the counts maps of Al-K X-rays in the Event-Driven readout mode, which is due to region-to-region variation of the pedestal voltages at the input to the comparator circuit. The lowest available threshold energy is 1.1keV for a small region in the device where the non-uniformity is minimized. The noise of the charge sensitive amplifier at the sense node and the noise related to the trigger output function are ∼18e− (rms) and ∼13e− (rms), respectively.

Magnitude Agreement, Occurrence Consistency, and Elevation Dependency of Satellite-Based Precipitation Products over the Tibetan Plateau

Satellite remote sensing is a practical technique to estimate global precipitation with adequate spatiotemporal resolution in ungauged regions. However, the performance of satellite-based precipitation products is variable and uncertain for the Tibetan Plateau (TP) because of its complex terrain and climate conditions. In this study, we evaluated the abilities of nine widely used satellite-based precipitation products over the Eastern Tibetan Plateau (ETP) and quantified precipitation dynamics over the entire TP. The evaluation was carried out from three aspects, i.e., magnitude agreement, occurrence consistency, and elevation dependency, from grid-cell to regional scales. The results show that the nine satellite-based products exhibited different agreement with gauge-based reference data with median correlation coefficients ranging from 0.15 to 0.95. Three products (climate hazards group infrared precipitation with stations (CHIRPS), multi-source weighted-ensemble precipitation (MSWEP), and tropical rainfall measuring mission multi-satellite precipitation analysis (TMPA)) generally presented the best performance with the reference data, even in complex terrain regions, given their root mean square errors (RMSE) of less than 25 mm/mon. The climate prediction center merged analysis of precipitation (CMAP) product has relatively coarse spatial resolution, but it also exhibited good performance with a bias of less than 20% in watershed scale. Two other products (precipitation estimation from remotely sensed information using artificial neural networks-cloud classification system (PER-CCS) and climate prediction center morphing technique-raw (CMORPH-RAW)) overestimated precipitation with median RMSEs of 87 mm/mon and 45 mm/mon, respectively. All the precipitation products generally exhibited better agreement with the reference data for rainy season and lower-elevation regions. All of the products captured precipitation occurrence well, with hit event over 60%, and similar percentages of missed and false event. According to the evaluation, the four products (CHIRPS, MSWEP, TMPA, and CMAP) revealed that the annual precipitation over the TP fluctuated between 333 mm/yr and 488 mm/yr during the period 2003 to 2015. The study indicates the importance of integration of multiple data sources and post-processing (e.g., gauge data fusion and elevation correction) for satellite-based products and have implications for selection of suitable precipitation products for hydrological modeling and water resources assessment for the TP.

Tumor/normal genomic profiling in patients with metastatic solid tumors identifies pathogenic germline variants of therapeutic importance.

1501 Background: Tumor molecular profiling via next-generation sequencing (NGS) is routinely utilized to direct patients toward clinical trials of targeted therapeutics. NGS testing of paired tumor/normal samples identifies incidental pathogenic germline variants (PGVs), having potential implications for patients and their families. Methods: From 2011-2018, 1,015 patients with metastatic, refractory solid tumors underwent targeted (1700 genes) exome and transcriptome sequencing of matched tumor/normal samples through the Michigan Oncology Sequencing program. Identified PGVs that conferred increased cancer risk or were associated with certain autosomal recessive conditions were reported to the treating oncologist. Chart reviews were conducted every 3 months to assess whether PGV identification impacted treatment decision making. Results: 169 PGVs were identified in 160 unique patients (15.8% of cohort). 69 PGVs (41%) harbored a clear somatic second hit event in the tumor. PGVs associated with defects in double-strand DNA repair ( BRCA1, BRCA2, ATM, PALB2, BRIP1) or DNA mismatch repair ( MLH1, MSH2 and PMS2) were identified in 49 patients (5% of cohort, 31% of patients with PGVs), 37 of which had not previously been identified. 14 PGVs in DNA double-strand repair and 7 PGVs in DNA mismatch repair were identified in cancer types not commonly associated with hereditary breast ovarian cancer or Lynch syndromes, including cancers of unknown primary origin and sarcomas. 7 patients received a PARP inhibitor (PARPi), 3 patients received an immune checkpoint inhibitor (ICI) and 1 patient received both PARPi and ICI therapy on the basis of a PGV in DNA repair. 6 patients achieved clinical benefit, defined as time on treatment ≥ 6 months. A patient with cancer of unknown primary origin and PGV in MSH2 achieved exceptional response to ICI therapy, with complete response ongoing and lasting 23 months. Conclusions: Targeted NGS of matched tumor/normal samples identified PGVs in about 1 in every 6 patients with metastatic solid tumors. Approximately 40% of PGVs are associated with a somatic second hit in the tumor, supporting their role in tumor pathogenesis. Unexpected PGVs with therapeutic implications are identified in patients with diverse cancer types, providing opportunities to use targeted therapies with potential for significant clinical benefit. Given this finding, testing for PGVs in DNA repair genes should be considered in all patients with metastatic solid tumor malignancies.

Radiation Oncology Learning Environment and Near Miss Events

Near misses, defined by harm averted due to chance or intervention, are low-cost learning opportunities in radiation oncology. We examine effects of near miss type and learning environment characteristics, such as psychological safety (PS) and time for reflection (TF), on incident reporting and recognition as success versus failure. We posit that perceiving the incident as success is correlated with perceptions of departmental willingness to report (WTR), and that these ratings would differ by near miss type. We also assess the relationship of psychological safety (PS) and time for reflection (TR) with departmental WTR. We administered a survey to members of a radiation oncology department with an incident learning system (ILS). The survey presented six incidents (4 near misses, 1 control, 1 hit) for a patient receiving intravenous contrast: process-based catch with harm averted by systematic creatinine check; good catch with harm averted by staff incidentally checking creatinine; could-have happened harm averted by chance normal creatinine; almost-happened harm with patient’s creatinine elevated and no sequelae; hit event with kidney injury; and control event with normal, checked creatinine and no sequelae. Subjects rated each event for success and departmental WTR on a 1-7 Likert scale, and answered validated PS and TF instruments. ANOVA and ordered logistic regression were used to assess WTR and success rating differences among near miss types, correlations with PS and TR, and real incidents coded as near miss in the department’s ILS database between 2014-2018. The survey yielded 97 of 127 responses (76.4%). Within each near miss type, success rating and WTR were negatively correlated (p<0.0001). There was no difference in WTR nor success ratings among near miss types (p=0.87). Male subjects exhibited a greater trend towards WTR hit events compared to female subjects (p=0.058). TR showed a positive trend with almost-happened events (p=0.085) and was significantly correlated with departmental WTR hits (p=0.007). However, TR showed a negative trend in real ILS reporting of near miss incidents (p=0.077). PS for attending physicians was significantly greater than that for therapists (5.68 vs. 3.56, p = 0.001). TF for therapists (4.31, p=0.034), physicists/dosimetrists (4.18, p=0.007), and nurses/medical assistants (4.33, p=0.048) were significantly less compared to that of physicians (5.81). In free text responses, subjects described the ILS as a platform to report “problems.” Near misses perceived as failures (vs. successes) are more likely to be reported, which corroborates the perception of the ILS as a platform to share problems. Greater time for reflection is correlated with the perception of others’ willingness to report harmful events, though less reflection time may be associated with personal ILS submissions, perhaps due to hierarchical role differences.

Modulation of Beta Oscillations for Implicit Motor Timing in Primate Sensorimotor Cortex during Movement Preparation.

Motor timing is an important part of sensorimotor control. Previous studies have shown that beta oscillations embody the process of temporal perception in explicit timing tasks. In contrast, studies focusing on beta oscillations in implicit timing tasks are lacking. In this study, we set up an implicit motor timing task and found a modulation pattern of beta oscillations with temporal perception during movement preparation. We trained two macaques in a repetitive visually-guided reach-to-grasp task with different holding intervals. Spikes and local field potentials were recorded from microelectrode arrays in the primary motor cortex, primary somatosensory cortex, and posterior parietal cortex. We analyzed the association between beta oscillations and temporal interval in fixed-duration experiments (500ms as the Short Group and 1500ms as the Long Group) and random-duration experiments (500ms to 1500ms). The results showed that the peak beta frequencies in both experiments ranged from 15Hz to 25Hz. The beta power was higher during the hold period than the movement (reach and grasp) period. Further, in the fixed-duration experiments, the mean power as well as the maximum rate of change of beta power in the first 300ms were higher in the Short Group than in the Long Group when aligned with the Center Hit event. In contrast, in the random-duration experiments, the corresponding values showed no statistical differences among groups. The peak latency of beta power was shorter in the Short Group than in the Long Group in the fixed-duration experiments, while no consistent modulation pattern was found in the random-duration experiments. These results indicate that beta oscillations can modulate with temporal interval in their power mode. The synchronization period of beta power could reflect the cognitive set maintaining working memory of the temporal structure and attention.

SUN-047 Germline and Somatic Mutations in DICER1 Gene Associated with Different Hereditary Tumours in Paediatric Patients

Carriers of germline DICER1 mutations are predisposed to a rare cancer syndrome, the DICER1 syndrome, associated with tumours such as pleuropulmonary blastoma (PPB), ovarian Sertoli-Leydig cell tumours (SLCT), multinodular goiter (MNG), cystic nephroma (CN), embryonal rhabdomyosarcoma (ERMS) and others. Germline mutations in DICER1 cause an alteration in miRNAs processing, deregulating target oncogenes and leading to elevated risk of tumorigenesis. In most reported cases, there is a heterozygous germline mutation and a somatic second hit mutation. Aim: Analyze the presence of germline and somatic alterations in the DICER1 gene in 6 patients with paediatric tumours associated with DICER1 spectrum. Methods: Automated sequencing of DICER1 gene from gDNA extracted from blood and formalin-fixed, paraffin-embedded tumour tissues of affected subjects and relatives. Cases: 5 girls (P1-P5) and 1 boy (P6), (P1: bilateral SLCT, P2 and P3: SLCT and MNG, P4: MNG and uterine myosarcoma, P5: vaginal rhabdomyosarcoma, and P6: CN). Chronological age at diagnostic was 5, 12, 15, 16, 13 y 2, respectively. Results: We detected 5 novel heterozygous mutations: p.Trp1098* in P1, p.Phe351fs*1 in P2, p.Arg1596Glyfs*24 in P4, c.3269+1G>A in P5, p.Asp244Glyfs*27 in P6, and one previously described heterozygous deletion p.Asp1437Metfs*16 in P3.These mutations (P1-P4 and P6) predict the presence of a truncated protein losing its essential domains for the enzymatic activity and, in one P5 an alteration in the splicing process. The tissue analysis revealed p.Asp1709Glu in MNG and p.Glu1705Lys in SLCT in P2, and p.Glu1705Lys in MNG in P3,previously described as hotspot somatic mutations. Conclusions: We report five novel germinal mutations in DICER1 gene and two somatic hotspot mutations in MNG and SLCT tissue samples. These findings confirm that a second hit event is involved in the mechanism of MNG and SLCT development. Molecular analysis of DICER1 gene allows to perform genetic counselling about familial recurrence risk.

Probabilistic Caching Based on Maximum Distance Separable Code in a User-Centric Clustered Cache-Aided Wireless Network

We investigate how the maximum-distance separable (MDS) coding can be incorporated into probabilistic caching to utilize the limited storage space efficiently. In a user-centric clustered wireless network, each caching helper node probabilistically caches a segment of MDS coded sequence of each file. The segment size is optimized to maximize the cache hit probability or successful file retrieval probability. We reveal that the best way of storing files is determined by the condition whether the average amount of MDS coded information stored for the requested file within a user’s cluster exceeds the amount required for file retrieval or not. In terms of the cache hit probability maximization, if the condition is not fulfilled, it is proved that storing the complete file with a low probability is optimal. Otherwise, storing either a segment as small as possible with a high probability or a complete file with a low probability, according to a given environment, is shown to be desirable. We also analyze the successful retrieval probability, which accounts for both a cache hit event and successful transmissions from multiple caching helper nodes. Since the successful retrieval probability is in an intractable form, to find the desirable segment size, the theoretically driven algorithms with low search complexity are developed.

Rare RELN variants affect Reelin-DAB1 signal transduction in autism spectrum disorder.

The Reelin-DAB1 signaling pathway plays a crucial role in regulating neuronal migration and synapse function. Although many rare heterozygous variants in the Reelin gene (RELN) have been identified in patients with autism spectrum disorder (ASD), most variants are still of unknown clinical significance. Also, genetic data suggest that heterozygous variants in RELN alone appear to be insufficient to cause ASD. Here, we describe the identification and functional characterization of rare compound heterozygous missense variants in RELN in a patient with ASD in whom we have previously reported hyperfunctional mTORC1 signaling of yet unknown etiology. Using iPSC-derived neural progenitor cells (NPCs) from this patient, we provide experimental evidence that the identified variants are deleterious and lead to diminished Reelin secretion and impaired Reelin-DAB1 signal transduction. Also, our results suggest that mTORC1 pathway overactivation may function as a second hit event contributing to downregulation of the Reelin-DAB1 cascade in patient-derived NPCs, and that inhibition of mTORC1 by rapamycin attenuates Reelin-DAB1 signaling impairment. Taken together, our findings point to an abnormal interplay between Reelin-DAB1 and mTORC1 networks in nonsyndromic ASD.

Biogenesis and regulatory hierarchy of phased small interfering RNAs in plants.

SummarySeveral varieties of small RNAs including microRNAs (miRNAs) and small interfering RNAs (siRNAs) are generated in plants to regulate development, genome stability and response to adverse environments. Phased siRNA (phasiRNA) is a type of secondary siRNA that is processed from a miRNA‐mediated cleavage of RNA transcripts, increasing silencing efficiency or simultaneously suppressing multiple target genes. Trans‐acting siRNAs (ta‐siRNAs) are a particular class of phasiRNA produced from noncoding transcripts that silence targets in trans. It was originally thought that ‘one‐hit’ and ‘two‐hit’ models were essential for processing distinct TAS precursors; however, a single hit event was recently shown to be sufficient at triggering all types of ta‐siRNAs. This review discusses the findings about biogenesis, targeting modes and regulatory networks of plant ta‐siRNAs. We also summarize recent advances in the generation of other phasiRNAs and their possible biological benefits to plants.

Verification of real-time WSA−ENLIL+Cone simulations of CME arrival-time at the CCMC from 2010 to 2016

The Wang-Sheeley-Arge (WSA)−ENLIL+Cone model is used extensively in space weather operations world-wide to model coronal mass ejection (CME) propagation. As such, it is important to assess its performance. We present validation results of the WSA−ENLIL+Cone model installed at the Community Coordinated Modeling Center (CCMC) and executed in real-time by the CCMC space weather team. CCMC uses the WSA−ENLIL+Cone model to predict CME arrivals at NASA missions throughout the inner heliosphere. In this work we compare model predicted CME arrival-times to in situ interplanetary coronal mass ejection leading edge measurements at Solar TErrestrial RElations Observatory-Ahead (STEREO-A), Solar TErrestrial RElations Observatory-Behind (STEREO-B), and Earth (Wind and ACE) for simulations completed between March 2010 and December 2016 (over 1,800 CMEs). We report hit, miss, false alarm, and correct rejection statistics for all three locations. For all predicted CME arrivals, the hit rate is 0.5, and the false alarm rate is 0.1. For the 273 events where the CME was predicted to arrive at Earth, STEREO-A, or STEREO-B, and was actually observed (hit event), the mean absolute arrival-time prediction error was 10.4 ± 0.9 h, with a tendency to early prediction error of −4.0 h. We show the dependence of the arrival-time error on CME input parameters. We also explore the impact of the multi-spacecraft observations used to initialize the model CME inputs by comparing model verification results before and after the STEREO-B communication loss (since September 2014) and STEREO-A sidelobe operations (August 2014–December 2015). There is an increase of 1.7 h in the CME arrival time error during single, or limited two-viewpoint periods, compared to the three-spacecraft viewpoint period. This trend would apply to a future space weather mission at L5 or L4 as another coronagraph viewpoint to reduce CME arrival time errors compared to a single L1 viewpoint.

Performance of Equity Linked Notes Versus Equity Portfolio

Barrier Reverse Convertible structured products have been in huge demand across the globe and are seen as a major part of the overall structured product market. The reverse convertible feature causes the product to deliver worst performing equity in case of a barrier hit event. Otherwise the product delivers regular coupon and complete principal amount at maturity. In this paper we present a simplified framework for investors to view the flipside of the investment and possible losses in the event of delivery of underlyings. We perform the return calculations in specified period window and compare against an equity portfolio investment during the same tenure. We also derive the factors and probabilities of various events which attribute to the performance of the product. We apply the same framework to 200 currently traded products and estimate the profit and losses to investors.

An Evaluation of Tropical Cyclone Genesis Forecasts from Global Numerical Models

Abstract Tropical cyclone (TC) forecasts rely heavily on output from global numerical models. While considerable research has investigated the skill of various models with respect to track and intensity, few studies have considered how well global models forecast TC genesis in the North Atlantic basin. This paper analyzes TC genesis forecasts from five global models [Environment Canada's Global Environment Multiscale Model (CMC), the European Centre for Medium-Range Weather Forecasts (ECMWF) global model, the Global Forecast System (GFS), the Navy Operational Global Atmospheric Prediction System (NOGAPS), and the Met Office global model (UKMET)] over several seasons in the North Atlantic basin. Identifying TCs in the model is based on a combination of methods used previously in the literature and newly defined objective criteria. All model-indicated TCs are classified as a hit, false alarm, early genesis, or late genesis event. Missed events also are considered. Results show that the models' ability to predict TC genesis varies in time and space. Conditional probabilities when a model predicts genesis and more traditional performance metrics (e.g., critical success index) are calculated. The models are ranked among each other, and results show that the best-performing model varies from year to year. A spatial analysis of each model identifies preferred regions for genesis, and a temporal analysis indicates that model performance expectedly decreases as forecast hour (lead time) increases. Consensus forecasts show that the probability of genesis noticeably increases when multiple models predict the same genesis event. Overall, this study provides a climatology of objectively identified TC genesis forecasts in global models. The resulting verification statistics can be used operationally to help refine deterministic and probabilistic TC genesis forecasts and potentially improve the models examined.

Neurofibromatosis: Etiology, Commonly Encountered Spinal Deformities, Common Complications and Pitfalls of Surgical Treatment

Neurofibromatosis 1 (NF-1) is a multisystemic, autosomal dominant genetic disorder. Skeletal complications usually present early in life and can be attributed to abnormalities of bone growth, remodeling, and repair, or can be secondary to nearby soft-tissue abnormalities complicating NF-1. Skeletal complications can be categorized as generalized or focal manifestations. The incidence of spinal deformities in association with NF-1 varies from 2% to 36%, with scoliosis being the most common. Both heritable and nonheritable factors contribute to the pathogenesis of spinal deformities in NF-1 patients. Traditionally, the spinal deformities are classified into dystrophic or nondystrophic. The pathophysiology of dystrophic curves is still uncertain, but may require a nonhereditary event, such as an adjacent tumor or a second hit event in local bone cells, leading to the underlying dysplasia. Dystrophic curves may result in scoliosis, kyphosis, or frequently, kyphoscoliosis. The goal of surgical management is to arrest the progression of deformity instead of achieving complete correction. The current state-of-the-art treatment for significant deformity is combined anterior and posterior spinal arthrodesis. Postoperative orthotic immobilization is almost always recommended in an effort to prevent pseudoarthrosis. The orthosis should be maintained until a fusion mass is obtained. Assessment of the fusion mass by computed tomography (CT) or magnetic resonance imaging (MRI) should be performed. Major complications, such as paraplegia, pseudoarthrosis, intraoperative hemorrhage, and postoperative progression of the deformity may occur. In an attempt to eliminate complications and achieve the best results, a multidisciplinary treatment strategy is needed. The intent of this article is to present the spinal deformities that are most commonly associated with NF-1, to identify the underlying biology of spinal deformities based on the most recent literature, and to address the common complications and pitfalls of their surgical management.

치아/복합레진 수복부의 중합 수축시 검출된 음향방출의 통계적 검증

치아의 와동에 수복된 치과용 복합레진을 광(LED) 조사를 통해 정화 수축시키면서 음향방출(acoustic emission, AE) 신호를 검출하였다. 비모수 통계법인 Mann-Whitney법과 Kruskal-Wallis법을 이용하여 시편의 재질과 계면의 접착조건에 따른 AE hit event 수와 최대진폭을 비교 평가하였다. PMMA와 치아시편으로부터 검출된 선호의 최대진폭은 정착조건에 따른 차이가 없었지만 스테인리스 시편으로부터 검출된 신호는 접착조건에 따라 최대 진폭의 차이가 있었다(p<0.05). AE hit event 수는 양호한 접착조건에서 시편의 재질에 따라 차이가 있었고(p<0.05), 세가지 재질의 시편 모두 접착조건이 양호한 실험에서 AE 신호가 적게 검출되었다. SEM을 이용하여 계면에 생성된 캡을 측정한 결과 AE가 많이 검출되고 검출된 신호의 최대 진폭이 큰 시편에서 갱의 폭이 넓고 형성 비율이 높았다. Acoustic emission (AE) signals are detected during the polymerization shrinkage of composite resin restoration in artificial dental ring according to various interfacial treatment conditions. AE amplitudes and the number of AE hit events were compared through the non-parametric statistics of Mann-Whitney method and Kruskal-Wallis method. The AE amplitudes detected from the PMMA and human tooth ring specimens were not significantly different according to adhesive conditions. The stainless steel ring specimen, meanwhile, had a difference in AE amplitude (p<0.05). The quantity of hit events for the human molar dentin specimens of the good bonding state was much less than that for the steel ring specimen but more than that for the PMMA ring specimen. For the same substrate, the better the bonding state, the less the AE hit events (p<0.05). The degree of marginal disintegration measured by SEM was proportional to the amount of AE hit events detected.

Tumor-specific exon 1 mutations could be the ‘hit event’ predisposing Rb2/p130 gene to epigenetic silencing in lung cancer

Genetic alterations in Rb2/p130 gene have been reported in several tumors, but till now there are insufficient and conflicting data linking the loss of pRb2/p130 expression with the mutational status of this gene in lung cancer. We recently reported that loss or lowering of pRb2/p130 expression is mainly due to aberrant Rb2/p130 promoter methylation, in retinoblastoma tumors, and indicated that epigenetic silencing of Rb2/p130 can impair its function to negatively regulate cell cycle progression as well as apoptotic response. In order to clarify Rb2/p130 gene inactivation in lung cancer, we investigated whether epigenetic events could impair the expression of this gene in NSLC. Here, we show that specific Rb2-exon 1 homozygous mutations, occurring in an Rb2/p130, region, rich in CpG dinucleotides, could be the 'hit event' that predispose this gene to epigenetic changes, leading to Rb2/p130 gene silencing in lung cancer. Moreover, these homozygous mutations, found in different tumor histotypes, could represent tumor-specific markers.

Monoclonal antibodies against leucoagglutinin-reactive human T-lymphocyte surface components. II. Studies on the mechanism of K46M-induced activation and determination of the frequency of responding cells.

A monoclonal antibody, K46M (IgM kappa), obtained after immunization with leucoagglutinin (La)-reactive T-cell surface components, stimulated human lymphocytes to proliferate. It induced maximal proliferation at greater than 20 micrograms IgM/ml after 3-4 days of culture. Cells stimulated by K46M produced interleukin 2 (IL-2) and gamma interferon (IFN-gamma) and expressed receptors for IL-2 and transferrin. The majority of the activated cells were phenotypically T cells as defined by monoclonal antibodies against CD3 and CD2, and an increase in the K46M-positive cells was also observed during the activation period. K46M-activated cells display major histocompatibility complex (MHC)-unrestricted cytotoxicity against several cultured target cells. The frequencies of the cytotoxic and of the proliferative precursor cells were determined using a limiting dilution assay. K46M seems to activate a larger fraction of cytotoxic precursor cells against Molt 4 than against K562, but the statistical significance of these observations requires further exploration. Both K46M or La activated 40% of PBL to proliferate, whereas 70% of PBL were induced by OKT3. However, the frequency of K46M-activated cells was 40% only when the lymphocytes were plated at low cell densities, i.e. less than 0.5 cells per well. At higher densities an inhibition of proliferation was seen that resulted in a biphasic response curve, indicating that the activation of PBL by K46M was not a single hit event. This was not found with either La or OKT3. Whether K46M, in contrast to OKT3 and La, activates a subpopulation with suppressor activity remains to be established.

Mechanism of cell-mediated cytotoxicity at the single-cell level: VII. Trigger of the lethal hit event is distinct for NK/K and LDCC effector cells as measured in the two-target conjugate assay

Normal human peripheral blood lymphocytes (PBL) express several in vitro cytotoxic functions, among which are natural killer (NK), antibody-dependent cellular cytotoxicity (ADCC), and lectin-dependent cellular cytotoxicity (LDCC). The relationship of these various cytotoxic functions and the identity of cells involved has been a subject of controversy. Recently it was reported that NK and K for ADCC can be mediated by the same cell, suggesting that they constitute in large part a single subpopulation with multiple cytotoxic functions. The ability of this NK/K effector cell to mediate LDCC was examined here using the two target conjugate assay. The effector cells were Ficoll-Hypaque PBL or LGL-enriched fractions. The targets used were K562 or MOLT for NK, RAJI coated with antibody for ADCC, and RAJI coated with PHA or Con A or modified by NaIO 4 for LDCC. In the two-target conjugate assay, one of the targets is fluorescein labeled for identification. The results show that (a) LDCC copurifies with NK/K and is enriched in the LGL fraction, as measured in both the 51Cr-release assay and the single-cell assay for cytotoxicity; (b) single effector cells simultaneously bind to NK or ADCC and LDCC targets, revealing that single cells bear binding receptors for all targets; and (c) single lymphocytes were not able to kill both bound NK/K and LDCC targets. However, significant two-target killing was obtained when both targets were NK targets, ADCC targets, LDCC targets, or one NK and one ADCC target. These results demonstrate that the NK and LDCC effector cells are distinct subpopulations copurified in the LGL fraction. In addition, the results show that lectin is unable to trigger globally an NK effector cell to mediate cytotoxicity against a bound NK insensitive target. Thus, although both NK and LDCC effector cells are present in the LGL fraction and can bind to both types of targets, the trigger of the lethal hit event is the function of specialized effector cells.

Towards a comprehensive user interface management system

A UIMS developed at the University of Toronto is presented. The system has two main components. The first is a set of tools to support the design and implementation of interactive graphics programs. The second is a run-time support package which handles interactions between the system and the user (things such as hit detection, event detection, screen updates, and procedure invocation), and provides facilities for logging user interactions for later protocol analysis. The design/implementation tool is a preprocessor, called MENULAY, which permits the applications programmer to use interactive graphics techniques to design graphics menus and their functionality. The output of this preprocessor is high-level code which can be compiled with application-specific routines. User interactions with the resulting executable module are then handled by the run-time support package. The presentation works through an example from design to execution in a step-by-step manner.