The ducky^{2J} Mutation in Cacna2d2 Results in Reduced Spontaneous Purkinje Cell Activity and Altered Gene Expression

The mouse mutant ducky and its allele ducky^{2J} represent a model for absence epilepsy characterized by spike-wave seizures and cerebellar ataxia. These mice have mutations in Cacna2d2, which encodes the α₂δ-2 calcium channel subunit. Of relevance to the ataxic phenotype, α₂δ-2 mRNA is strongly expressed in cerebellar Purkinje cells (PCs). The Cacna2d2du2J mutation results in a 2 bp deletion in the coding region and a complete loss of α₂δ-2 protein. Here we show that du^{2J}/du^{2J} mice have a 30% reduction in somatic calcium current and a marked fall in the spontaneous PC firing rate at 22°C, accompanied by a decrease in firing regularity, which is not affected by blocking synaptic input to PCs. At 34°C, du^{2J}/du^{2J} PCs show no spontaneous intrinsic activity. DU^{2J}/du^{2J} mice also have alterations in the cerebellar expression of several genes related to PC function. At postnatal day 21, there is an elevation of tyrosine hydroxylase mRNA and a reduction in tenascin-C gene expression. Although du^{2J}/+ mice have a marked reduction in α₂δ-2 protein, they show no fall in PC somatic calcium currents or increase in cerebellar tryrosine hydroxylase gene expression. However, du^{2J}/+ PCs do exhibit a significant reduction in firing rate, correlating with the reduction in α₂δ-2. A hypothesis for future study is that effects on gene expression occur as a result of a reduction in somatic calcium currents, whereas effects on PC firing occur as a long-term result of loss of α₂δ-2 and/or a reduction in calcium currents and calcium-dependent processes in regions other than the soma

Morgagni hernia repair in children over two decades: Institutional experience, systematic review, and meta-analysis of 296 patients

BACKGROUND/PURPOSE: Morgagni diaphragmatic hernia (MH) is rare. We report our experience based on routine patch use in MH repair to curb recurrence. A systematic review and meta-analysis were performed to study the recurrence and complications associated with minimally invasive surgery and the use of patch. METHODS: We retrospectively reviewed all cases of MH who underwent first-time repair in 2012-2017 in our institution to determine recurrence and complication rate. A MEDLINE search related to minimally invasive surgery (MIS) and patch repair of MH was conducted for systematic review. Eligible articles published from 1997-2017 with follow-up data available were included. Primary outcomes measured were recurrence and complication. Meta-analysis to compare open versus MIS and primary versus patch repair in the MIS group were performed in comparative cohorts. Continuous data were presented as median (range), and statistical significance was P<0.05. RESULTS: In our institution, 12 consecutive patients aged 17-month-old (22 days-7 years), underwent laparoscopic patch repair of MH, with one conversion to laparotomy. No recurrence or significant complication occurred over a follow-up period of 8 months (1-48 months). Thirty-six articles were included from literature review and were combined with the current series. All were retrospective case reports or series, of which 6 were comparative cohorts with both MIS and open repairs. A total of 296 patients from 37 series were ultimately used for analysis: 80 had open repair (4 patch) and 216 had MIS repair (32 patch), with a patch rate of 12%. There were 13 recurrences (4%): no difference between open and MIS repairs (4/80 vs 9/216, p=0.75); recurrence rate following primary repair was 13/260 (5%), but no recurrence occurred with 36 patch repairs. Meta-analysis showed no difference in recurrence between open and MIS repair (p=0.83), whereas patch repair was associated with 14% less recurrence compared with primary repair, although it did not reach statistical significance (p=0.12). There were 13 complications (5%): no difference between open and MIS repairs (5/80 vs 8/216, p=0.35). One small bowel obstruction occurred in a patient who had laparoscopic patch repair. CONCLUSION: In MH, recurrence and complication rates are comparable between MIS and open repairs. Use of patch appeared to confer additional benefit in reducing recurrence. TYPE OF STUDY: Systematic review LEVEL OF EVIDENCE: 3A

Cytosine-to-Uracil Deamination by SssI DNA Methyltransferase

The prokaryotic DNA(cytosine-5)methyltransferase M.SssI shares the specificity of eukaryotic DNA methyltransferases (CG) and is an important model and experimental tool in the study of eukaryotic DNA methylation. Previously, M.SssI was shown to be able to catalyze deamination of the target cytosine to uracil if the methyl donor S-adenosyl-methionine (SAM) was missing from the reaction. To test whether this side-activity of the enzyme can be used to distinguish between unmethylated and C5-methylated cytosines in CG dinucleotides, we re-investigated, using a sensitive genetic reversion assay, the cytosine deaminase activity of M.SssI. Confirming previous results we showed that M.SssI can deaminate cytosine to uracil in a slow reaction in the absence of SAM and that the rate of this reaction can be increased by the SAM analogue 5’-amino-5’-deoxyadenosine. We could not detect M.SssI-catalyzed deamination of C5-methylcytosine (m5C). We found conditions where the rate of M.SssI mediated C-to-U deamination was at least 100-fold higher than the rate of m5C-to-T conversion. Although this difference in reactivities suggests that the enzyme could be used to identify C5-methylated cytosines in the epigenetically important CG dinucleotides, the rate of M.SssI mediated cytosine deamination is too low to become an enzymatic alternative to the bisulfite reaction. Amino acid replacements in the presumed SAM binding pocket of M.SssI (F17S and G19D) resulted in greatly reduced methyltransferase activity. The G19D variant showed cytosine deaminase activity in E. coli, at physiological SAM concentrations. Interestingly, the C-to-U deaminase activity was also detectable in an E. coli ung+ host proficient in uracil excision repair

The RR Lyrae Distance Scale

We review seven methods of measuring the absolute magnitude M_V of RR Lyrae stars in light of the Hipparcos mission and other recent developments. We focus on identifying possible systematic errors and rank the methods by relative immunity to such errors. For the three most robust methods, statistical parallax, trigonometric parallax, and cluster kinematics, we find M_V (at [Fe/H] = -1.6) of 0.77 +/- 0.13, 0.71 +/- 0.15, 0.67 +/- 0.10. These methods cluster consistently around 0.71 +/- 0.07. We find that Baade-Wesselink and theoretical models both yield a broad range of possible values (0.45-0.70 and 0.45-0.65) due to systematic uncertainties in the temperature scale and input physics. Main-sequence fitting gives a much brighter M_V = 0.45 +/- 0.04 but this may be due to a difference in the metallicity scales of the cluster giants and the calibrating subdwarfs. White-dwarf cooling-sequence fitting gives 0.67 +/- 0.13 and is potentially very robust, but at present is too new to be fully tested for systematics. If the three most robust methods are combined with Walker's mean measurement for 6 LMC clusters, V_{0,LMC} = 18.98 +/- 0.03 at [Fe/H] = -1.9, then mu_{LMC} = 18.33 +/- 0.08.Comment: Invited review article to appear in: `Post-Hipparcos Cosmic Candles', A. Heck & F. Caputo (Eds), Kluwer Academic Publ., Dordrecht, in press. 21 pages including 1 table; uses Kluwer's crckapb.sty LaTeX style file, enclose

Globular Cluster Distance Determinations

The present status of the distance scale to Galactic globular clusters is reviewed. Six distance determination techniques which are deemed to be most reliable are discussed in depth. These different techniques are used to calibrate the absolute magnitude of the RR Lyrae stars. The various calibrations fall into three groups. Main sequence fitting using Hipparcos parallaxes, theoretical HB models and the RR Lyrae in the LMC all favor a bright calibration, implying a `long' globular cluster distance scale. White dwarf fitting and the astrometric distances yield a somewhat fainter RR Lyrae calibration, while the statistical parallax solution yields faint RR Lyrae stars implying a `short' distance scale to globular clusters. Various secondary distance indicators discussed all favor the long distance scale. The `long' and `short' distance scales differ by (0.31+/-0.16) mag. Averaging together all of the different distance determinations yields Mv(RR) = (0.23+/-0.04)([Fe/H] + 1.6) + (0.56+/-0.12) mag.Comment: Invited review article to appear in: `Post-Hipparcos Cosmic Candles', A. Heck & F. Caputo (Eds), Kluwer Academic Publ., Dordrecht, in pres

Evaluation of the limitations and methods to improve rapid phage-based detection of viable Mycobacterium avium subsp. paratuberculosis in the blood of experimentally infected cattle

Background Disseminated infection and bacteraemia is an underreported and under-researched aspect of Johne’s disease. This is mainly due to the time it takes for Mycobacterium avium subsp. paratuberculosis (MAP) to grow and lack of sensitivity of culture. Viable MAP cells can be detected in the blood of cattle suffering from Johne’s disease within 48 h using peptide-mediated magnetic separation (PMMS) followed by bacteriophage amplification. The aim of this study was to demonstrate the first detection of MAP in the blood of experimentally exposed cattle using the PMMS-bacteriophage assay and to compare these results with the immune response of the animal based on serum ELISA and shedding of MAP by faecal culture. Results Using the PMMS-phage assay, seven out of the 19 (37 %) MAP-exposed animals that were tested were positive for viable MAP cells although very low numbers of MAP were detected. Two of these animals were positive by faecal culture and one was positive by serum ELISA. There was no correlation between PMMS-phage assay results and the faecal and serum ELISA results. None of the control animals (10) were positive for MAP using any of the four detection methods. Investigations carried out into the efficiency of the assay; found that the PMMS step was the limiting factor reducing the sensitivity of the phage assay. A modified method using the phage assay directly on isolated peripheral blood mononuclear cells (without PMMS) was found to be superior to the PMMS isolation step. Conclusions This proof of concept study has shown that viable MAP cells are present in the blood of MAP-exposed cattle prior to the onset of clinical signs. Although only one time point was tested, the ability to detect viable MAP in the blood of subclinically infected animals by the rapid phage-based method has the potential to increase the understanding of the pathogenesis of Johne’s disease progression by warranting further research on the presence of MAP in blood