Pathology of the defunctioned rectum in ulcerative colitis.

Faecal stream diversion may induce inflammatory changes in the defunctioned segment of the large intestine. These changes are predominantly mucosal, although confusing histological features including granulomas may be present. The pathology of 15 defunctioned rectal stumps has been studied. All patients had previously undergone urgent total colectomy for ulcerative colitis and rectal stumps had been left in situ while they awaited pelvic ileal reservoir construction. All rectal stumps showed predominantly mucosal disease but there were additional features such as florid lymphoid follicular hyperplasia (12 cases), transmural inflammation (nine cases), granulomas (four cases), fissures (eight cases), and changes akin to ischaemia or to pseudomembraneous colitis (four cases). These changes may result from a combination of defunctioning and of active ulcerative proctitis. Some induce a histological appearance that may mimic Crohn's disease. Nevertheless review of all 15 colectomy specimens showed unequivocal ulcerative colitis and none of the patients has subsequently shown any clinical, radiological, or pathological evidence to support a diagnosis of Crohn's disease. Histology of the rectal stump in ulcerative colitis may lead to an erroneous diagnosis of Crohn's disease and the patient may subsequently be denied the advantage of a pelvic ileal reservoir.     

Detection of genomic deletions of PKP2 in arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited myocardial disease that predominantly affects the right ventricle and is associated with ventricular arrhythmias that may lead to sudden cardiac death. Mutations within at least seven separate genes have been identified to cause ARVC, however a genetic culprit remains elusive in approximately 50% of cases. Although negative genetic testing may be secondary to pathogenic mutations within undiscovered genes, an alternative explanation may be the presence of large deletions or duplications involving known genes. These large copy number variants may not be detected with standard clinical genetic testing which is presently limited to direct DNA sequencing. We describe two cases of ARVC possessing large deletions involving plakophilin‐2 (PKP2) identified with microarray analysis and/or multiplex ligation‐dependent probe amplification (MLPA) that would have been classified as genotype negative with standard clinical genetic testing. A deletion of the entire coding region of PKP2 excluding exon 1 was identified in patient 1 and his son. In patient 2, MLPA analysis of PKP2 revealed deletion of the entire gene with subsequent microarray analysis demonstrating a de novo 7.9 Mb deletion of chromosome 12p12.1p11.1. These findings support screening for large copy number variants in clinically suspected ARVC cases without clear disease causing mutations following initial sequencing analysis.     

Age-dependent neurological phenotypes in a mouse model of PRRT2-related diseases

Paroxysmal kinesigenic dyskinesia is an episodic movement disorder caused by dominant mutations in the proline-rich transmembrane protein PRRT2, with onset in childhood and typically with improvement or resolution by middle age. Mutations in the same gene may also cause benign infantile seizures, which begin in the first year of life and typically remit by the age of 2 years. Many details of PRRT2 function at the synapse, and the effects of mutations on neuronal excitability in the pathophysiology of epilepsy and dyskinesia, have emerged through the work of several groups over the last decade. However, the age dependence of the phenotypes has not been explored in detail in transgenic models. Here, we report our findings in heterozygous and homozygous Prrt2 knockout mice that recapitulate the age dependence of dyskinesia seen in the human disease. We show that Prrt2 deletion reduces the levels of synaptic proteins in a dose-dependent manner that is most pronounced at postnatal day 5 (P5), attenuates at P60, and disappears by P180. In a test for foot slippage while crossing a balance beam, transient loss of coordination was most pronounced at P60 and less prominent at age extremes. Slower traverse time was noted in homozygous knockout mice only, consistent with the ataxia seen in rare individuals with biallelic loss of function mutations in Prrt2. We thus identify three age-dependent phenotypic windows in the mouse model, which recapitulate the pattern seen in humans with PRRT2-related diseases.

     

Congruency and responsiveness of perceived exertion and time-to-end-point during an intermittent isometric fatigue task

The aims of this study were (1) to investigate the relationship between self-perception of effort and task duration in an intermittent isometric fatigue trial (IIF) and (2) to evaluate the capability of two assessment paradigms (perceived exertion; perceived task duration) to reflect changes in IIF intensity. Fifteen participants performed two IIF tasks of the knee extensors at intensities of 60 and 70 % of daily peak force, each separated by 48–72 h. Ordering of the tasks was counter-balanced and participants were blinded to the precise intensity of each IIF. A category-ratio scale (CR-10) and visual analogue scale were used during each IIF task to record measures of perceived exertion and perceived task duration, respectively. Measures were recorded at 10 % intervals across the relative duration of each IIF task. Pearson product-moment correlation coefficients revealed strong positive correlations (r > 0.99; p < 0.01) between completed task duration and both perceptual scales at the two IIF intensities. Separate two-way repeated measures ANOVAs of CR-10 and perceived task duration responses revealed significant main effects for time only (F _[2.2,30.1] = 126.8; p < 0.001; F _[2.6,36.8] = 117.2; p < 0.001, CR-10 and perceived task duration, respectively). The results suggest that perceived exertion and perceived task duration are equally effective predictors of IIF end-point. However, neither measure was sufficiently responsive to discriminate between 10 % changes in exercise intensity.     

Multicolor structured illumination microscopy and quantitative control of polychromatic light with a digital micromirror device

Linear structured illumination microscopy (SIM) is a super-resolution microscopy technique that does not impose photophysics requirements on fluorescent samples. Multicolor SIM implementations typically rely on liquid crystal on silicon (LCoS) spatial light modulators (SLM’s) for patterning the excitation light, but digital micromirror devices (DMD’s) are a promising alternative, owing to their lower cost and higher speed. However, existing coherent DMD SIM implementations use only a single wavelength of light, limited by the lack of efficient approaches for solving the blazed grating effect for polychromatic light. We develop the requisite quantitative tools, including a closed form solution of the blaze and diffraction conditions, forward models of DMD diffraction and pattern projection, and a model of DMD aberrations. Based on these advances, we constructed a three-color DMD microscope, quantified the effect of aberrations from the DMD, developed a high-resolution optical transfer function measurement technique, and demonstrated SIM on fixed and live cells. This opens the door to applying DMD’s in polychromatic applications previously restricted to LCoS SLM’s.