Substrate degradation by the anaphase promoting complex occurs during mitotic slippage

Microtubule targeting drugs are successful in chemotherapy because they indefinitely activate the spindle assembly checkpoint. The spindle assembly checkpoint monitors proper attachment of all kinetochores to microtubules and tension between the kinetochores of sister chromatids to prevent premature anaphase entry. To this end, the activated spindle assembly checkpoint suppresses the E3 ubiquitin ligase activity of the anaphase-promoting complex (APC). In the continued presence of conditions that activate the spindle assembly checkpoint, cells eventually escape from mitosis by "slippage". It has not been directly tested whether APC activation accompanies slippage. Using cells blocked in mitosis with the microtubule assembly inhibitor nocodazole, we show that mitotic APC substrates are degraded upon mitotic slippage. To confirm that APC is normally activated upon mitotic slippage we have found that knockdown of Cdc20 and Cdh1, two mitotic activators of APC, prevents the degradation of APC substrates during mitotic slippage. We provide the first direct demonstration that despite conditions that activate the spindle checkpoint, APC is indeed activated upon mitotic slippage of cells to interphase cells. Activation of the spindle checkpoint by microtubule targeting drugs used in chemotherapy may not indefinitely prevent APC activation.

Anatomical background and generalized detectability in tomosynthesis and cone-beam CT

PURPOSE

Anatomical background presents a major impediment to detectability in 2D radiography as well as 3D tomosynthesis and cone-beam CT (CBCT). This article incorporates theoretical and experimental analysis of anatomical background "noise" in cascaded systems analysis of 2D and 3D imaging performance to yield "generalized" metrics of noise-equivalent quanta (NEQ) and detectability index as a function of the orbital extent of the (circular arc) source-detector orbit.

METHODS

A physical phantom was designed based on principles of fractal self-similarity to exhibit power-law spectral density (kappa/Fbeta) comparable to various anatomical sites (e.g., breast and lung). Background power spectra [S(B)(F)] were computed as a function of source-detector orbital extent, including tomosynthesis (approximately 10 degrees -180 degrees) and CBCT (180 degrees + fan to 360 degrees) under two acquisition schemes: (1) Constant angular separation between projections (variable dose) and (2) constant total number of projections (constant dose). The resulting S(B) was incorporated in the generalized NEQ, and detectability index was computed from 3D cascaded systems analysis for a variety of imaging tasks.

RESULTS

The phantom yielded power-law spectra within the expected spatial frequency range, quantifying the dependence of clutter magnitude (kappa) and correlation (beta) with increasing tomosynthesis angle. Incorporation of S(B) in the 3D NEQ provided a useful framework for analyzing the tradeoffs among anatomical, quantum, and electronic noise with dose and orbital extent. Distinct implications are posed for breast and chest tomosynthesis imaging system design-applications varying significantly in kappa and beta, and imaging task and, therefore, in optimal selection of orbital extent, number of projections, and dose. For example, low-frequency tasks (e.g., soft-tissue masses or nodules) tend to benefit from larger orbital extent and more fully 3D tomographic imaging, whereas high-frequency tasks (e.g., microcalcifications) require careful, application-specific selection of orbital extent and number of projections to minimize negative effects of quantum and electronic noise.

CONCLUSIONS

The complex tradeoffs among anatomical background, quantum noise, and electronic noise in projection imaging, tomosynthesis, and CBCT can be described by generalized cascaded systems analysis, providing a useful framework for system design and optimization.

Increased prevalence of white matter hyperintensities in patients with panic disorder

The aim of the current study is to compare the prevalence, severity and location of cerebral white matter hyperintensities (WMH) between patients with panic disorder (PD) and healthy control subjects. Patients with PD (n = 24) and matched healthy control subjects (n = 24) were scanned using a 3.0 Tesla whole-body magnetic resonance scanner. Axial T2-weighted and fluid-attenuated inversion recovery images were acquired and evaluated for the prevalence, severity and location of WMH using the modified composite scale of Fazekas and Coffey and coded separately for deep and periventricular WMH. Logistic regression analyses were used to assess the association between WMH and the diagnosis of PD. A greater severity of total WMH was associated with a diagnosis of PD in a dose-dependent pattern (odds ratio [OR] = 8.8, P = 0.005 for mild WMH; OR = 27.7, P = 0.007 for moderate to severe WMH). Deep WMH, where most group differences originated, were predominantly located in the frontal region of the brain (n = 16 in PD, n = 1 in control). The current report is the first study to report an increased prevalence of WMH in patients with PD.

Higher surgical training in ophthalmology: trends in cumulative surgical experience 1993-2008

INTRODUCTION

Recent years have seen significant changes in the provision surgical training for ophthalmology. The aim of this study is to establish the patterns in long-term trends of cumulative surgical experience of ophthalmology trainees in the United Kingdom.

MATERIALS AND METHODS

Data were obtained from the department of training and education at the Royal College of Ophthalmologists (RCOphth). The cumulative surgical experience of all ophthalmology higher surgical trainees attaining accreditation, CCST, or CCT between 1993-2001 and 2005-2008 was included for descriptive analysis.

RESULTS

Cumulative cataract surgical experience per trainee has been relatively stable at levels between 500 and 600 for most years. The cumulative experience vitreoretinal and corneal graft surgery have historically been low with a large outlier effect, although trends demonstrate a decrease in the median numbers of procedures. Squint surgery has seen a downward trend with a decrease in the median numbers from 121 in 1993 to 43 in 2008. Oculoplastics procedures demonstrate a decrease in overall numbers from 46 in 1993 to 15 in 2001. A jump from 2005 coincides with changes in the definition of what is counted as an oculoplastics procedure. The role of the RCOphth in legislating minimum levels of experience has had an impact on the data distribution manifest by the truncation of the inferior quartile of many of the dataspreads.

DISCUSSION

These data demonstrate that although the cumulative experience of cataract surgery for trainees has remained stable, there has been a reduction in the median numbers of subspecialty procedures performed over the past 15 years.

A public image database to support research in computer aided diagnosis

The Public Lung Database to address drug response (PLD) has been developed to support research in computer aided diagnosis (CAD). Originally established for applications involving the characterization of pulmonary nodules, the PLD has been augmented to provide initial datasets for CAD research of other diseases. In general, the best performance for a CAD system is achieved when it is trained with a large amount of well documented data. Such training databases are very expensive to create and their lack of general availability limits the targets that can be considered for CAD applications and hampers development of the CAD field. The approach taken with the PLD has been to make available small datasets together with both manual and automated documentation. Furthermore, datasets with special properties are provided either to span the range of task complexity or to provide small change repeat images for direct calibration and evaluation of CAD systems. This resource offers a starting point for other research groups wishing to pursue CAD research in new directions. It also provides an on-line reference for better defining the issues relating to specific CAD tasks.

The Generalized NEQ and Detectability Index for Tomosynthesis and Cone-Beam CT: From Cascaded Systems Analysis to Human Observers

PURPOSE

In the early development of new imaging modalities - such as tomosynthesis and cone-beam CT (CBCT) - an accurate predictive model for imaging performance is particularly valuable in identifying the physical factors that govern image quality and guiding system optimization. In this work, a task-based cascaded systems model for detectability index is proposed that describes not only the signal and noise propagation in the 2D (projection) and 3D (reconstruction) imaging chain but also the influence of background anatomical noise. The extent to which generalized detectability index provides a valid metric for imaging performance was assessed through direct comparison to human observer experiments.

METHODS

Detectability index (d') was generalized to include anatomical background noise in the same manner as the generalized noise-equivalent quanta (NEQ) proposed by Barrett et al. (Proc. SPIE Med. Imaging, Vol. 1090, 1989). Anatomical background noise was measured from a custom phantom designed to present power-law spectral density comparable to various anatomical sites (e.g., breast and lung). Theoretical calculations of d' as a function of the source-detector orbital extent (θtot) was obtained from a 3D cascaded systems analysis model for tomosynthesis and cone-beam CT (CBCT). Four model observers were considered in the calculation of d': prewhitening (PW), non-prewhitening (NPW), prewhitening with eye filter and internal noise (PWE), and non-prewhitening with eye filter and internal noise (NPWE). Human observer performance was measured from 9AFC tests for a variety of idealized imaging tasks presented within a clutter phantom. Theoretical results (d') were converted to area under the ROC curve (Az ) and compared directly to human observer performance as a function of imaging task and orbital extent.

RESULTS

Theoretical results demonstrated reasonable correspondence with human observer response for all tasks across the continuum in θtot ranging from low-angle tomosynthesis (θtot ~10°) to CBCT (θtot ~180°). Both theoretical and experimental Az were found to increase with acquisition angle, consistent with increased rejection of out-of-plane clutter for larger tomosynthesis angle. Of the four theoretical model observers considered, the prewhitening models tended to overestimate real observer performance, while the non-prewhitening models demonstrated reasonable agreement.

CONCLUSIONS

Generalized detectability index was shown to provide a meaningful metric for imaging performance, helping to bridge the gap between real observer performance and prevalent Fourier-based metrics based in first principles of spatial-frequency-dependent NEQ and imaging task.

SP600125 suppresses Cdk1 and induces endoreplication directly from G2 phase, independent of JNK inhibition

Cell cycle controls ensure that DNA replication (S phase) follows mitosis resulting in two precise copies of the genome. A failure of the control mechanisms can result in multiple rounds of DNA replication without cell division. In endoreplication, cells with replicated genomes bypass mitosis, then replicate their DNA again, resulting in polyploidy. Endoreplication from G2 phase lacks all hallmarks of mitosis. Using synchronized cells, we show that the c-Jun N-terminal kinase (JNK) inhibitor, SP600125, prevents the entry of cells into mitosis and leads to endoreplication of DNA from G2 phase. We show that cells proceed from G2 phase to replicate their DNA in the absence of mitosis. This effect of SP600125 is independent of its suppression of JNK activity. Instead, the inhibitory effect of SP600125 on mitotic entry predominantly occurs upstream of Aurora A kinase and Polo-like kinase 1, resulting in a failure to remove the inhibitory phosphorylation of Cdk1. Importantly, our results directly show that the inhibition of Cdk1 activity and the persistence of Cdk2 activity in G2 cells induces endoreplication without mitosis. Furthermore, endoreplication from G2 phase is independent of p53 control.

Measurement of the depth of maximum of extensive air showers above 10{18} eV

We describe the measurement of the depth of maximum, X{max}, of the longitudinal development of air showers induced by cosmic rays. Almost 4000 events above 10;{18} eV observed by the fluorescence detector of the Pierre Auger Observatory in coincidence with at least one surface detector station are selected for the analysis. The average shower maximum was found to evolve with energy at a rate of (106{-21}{+35}) g/cm{2}/decade below 10{18.24+/-0.05} eV, and (24+/-3) g/cm{2}/decade above this energy. The measured shower-to-shower fluctuations decrease from about 55 to 26 g/cm{2}. The interpretation of these results in terms of the cosmic ray mass composition is briefly discussed.

Effects of glucose level on early and long-term mortality after intracerebral haemorrhage: the Acute Brain Bleeding Analysis Study

AIMS/HYPOTHESIS

Admission hyperglycaemia is associated with a poor outcome in patients with ischaemic stroke. However, its prognostic effects after intracerebral haemorrhage (ICH) are still unclear.

METHODS

We prospectively enrolled patients with ICH at 33 centres in Korea between October 2002 and March 2004. A total of 1,387 patients who had ICH and underwent brain computed tomography within 48 h of symptom onset were included in the study (n = 1,387). Clinical information and radiological findings were collected at admission. Glucose levels were examined in relation to early (up to 30 days after ictus) and long-term (after 30 days) mortality rates using Cox regression analysis. To eliminate short-term effects, long-term mortality rate analysis was performed on surviving patients for more than 30 days.

RESULTS

The long-term mortality rate was 21.1% after a mean follow-up of 434.3 +/- 223.2 days and was found to increase significantly with glucose quartile (p < 0.001). Admission glucose level was an independent risk factor for early mortality (per mmol/l; adjusted HR 1.10 [95% CI 1.01-1.19]), but not for long-term mortality. Moreover, when analysis was restricted to patients without diabetes, glucose level was found to be an independent risk factor for post-ICH mortality (n = 1,119; adjusted HR 1.10 [95% CI 1.03-1.17]) and had marginal significance for early (p = 0.053) and long-term mortality (p = 0.09).

CONCLUSIONS/INTERPRETATION

We found that admission glucose levels were associated with early mortality after ICH. In patients without diabetes, admission glucose levels were associated with long-term mortality. We therefore suggest that intensive lowering of glucose level should be further investigated in ICH patients.