Mechanisms of sinoatrial pacemaker synchronization: a new hypothesis

A model of electrically coupled sinus node cells was used to investigate pacemaker coordination and conduction. Individual cells were simulated using differential equations describing transmembrane ionic currents. Intrinsic cycle lengths (periods) were adjusted by applying constant depolarizing or hyperpolarizing bias current, and cells were coupled through ohmic resistances to form two-dimensional arrays. Activation maps of 81-225 coupled cells showed an apparent wavefront conducting from a leading pacemaker region to the rest of the matrix even though the pattern actually resulted from mutual entrainment of all spontaneously beating cells. Apparent conduction time increased with increasing intercellular resistance. Appropriate selection of pacemaker cycle lengths and intercellular resistances permitted the accurate simulation of the activation sequence seen experimentally for the rabbit sinus node. Furthermore, a simulated acetylcholine pulse applied to a randomly selected 20% of the cells in this model produced a pacemaker shift that lasted several beats. These results support the hypothesis that sinus node synchronization occurs through a "democratic" process resulting from the phase-dependent interactions of thousands of pacemakers.     

Does experience predict observational kinematic assessment accuracy?

Observation of patients' movements forms an integral part of the development of therapeutic treatment plans for neurological patients. In this study we investigated the influence of clinical experience on the accuracy of observational kinematic assessment (OKA) of upper limb movements. Twenty-one physiotherapists and 15 students participated. The less experienced (LE) group ( n = 11) had a mean of 2.8 years ( &#45 1.8 years) of clinical experience and the highly experienced (HE) group ( n = 10) had a mean of 10.5 years ( &#45 2.2 years) of experience. The novice group (N) consisted of students in the third year of their Physiotherapy degree. Highly experienced, LE, and N participants observed the videotaped movements of healthy and neurologically impaired performers and made visual judgments about the speed, jerkiness, and path indirectness of performances, recording their judgments on visual analogue scales. We compared observers' judgments with kinematic indices derived from three-dimensional computer-assisted motion analysis to determine OKA accuracy. All groups of observers made moderate to highly accurate judgments with no significant differences between groups. Furthermore, inter-rater reliability was not experience-dependent. We discuss why experiential differences might be absent and provide suggestions for future development of OKA.     

Reuse of silver-palladium ceramic metal

The effect of various percentages of reused silver-palladium alloy on the bond strength of porcelain was considered. All-new metal and once-cast alloy with the addition of 50% new metal produced the highest bond values. Once-cast alloy with less than 50% new metal produced bond strength values that were significantly lower. When using this silver-palladium alloy, 50% new alloy should be added to each casting button, and buttons with questionable casting history should not be used.     

Autoantibodies to vascular smooth muscle are pathogenic for vasculitis

We have previously shown that microvascular smooth muscle activates CD4+ T lymphocytes in sterile co-culture, presents antigen, and produces inflammatory cytokines. Adoptive transfer of lymphocytes co-cultured with syngeneic smooth muscle cells to healthy recipient mice results in vasculitic lesions predominantly in postcapillary venules. The present study assessed the pathogenic role of immunoglobulin and B cells in a murine model of vasculitis. Here, we show that transferred B cells, including plasmablast cells, accumulated, persisted, and proliferated in lung and secondary lymphoid organs of recipient mice. The induction of vasculitis was accompanied by production of IgM and IgG2a autoantibodies specific for vascular smooth muscle intracellular antigens. Circulating immunoglobulin had a pathogenic role in this vasculitis model, because the disease could be induced by transfer of serum from vasculitic mice to untreated animals but not by transfer of serum depleted of anti-smooth muscle autoantibodies. Additionally, the pathogenic mechanisms triggered by the transfer of vasculitogenic serum were dependent on T lymphocytes because both wild-type and B cell-deficient mice developed the disease after serum transfer, whereas RAG2-deficient mice did not. Thus, immunoglobulin and cell-mediated pathways work in concert to produce vasculitis in this model.     

Needle-free skin patch vaccination method for anthrax

Three immunizations of mice with recombinant protective antigen (rPA) by transcutaneous immunization (TCI) induced long-term neutralizing antibody titers that were superior to those obtained with aluminum-adsorbed rPA. In addition, rPA alone exhibited adjuvant activity for TCI. Forty-six weeks after completion of TCI, 100% protection was observed against lethal anthrax challenge.     

Requirements for CD4(+) T cell levels in acute Mycobacterium bovis strain bacille Calmette Guerin (BCG)-induced granulomas differ for optimal mycobacterial control versus granuloma formation

Bacille Calmette Guérin (BCG)-induced granulomas contain T cells that express a broad TCR repertoire even at the level of the individual lesion. We have developed a BCG infection model in mice having only one T cell specific for a recombinant BCG epitope expressed in a lipoprotein fusion protein. Here we report that the single T cell model induces well-formed granulomas, but has weaker protection than that conferred by wild-type granulomas. This finding correlates with lower CD4(+) T cell recruitment into acute granulomas (3 weeks post infection). Chronic granulomas (6 weeks post infection) contain similar proportions of CD4(+) T cells in both models, but in the single T cell model the proportion of leukocyte function-associated antigen-1 low, non-IFNgamma-producing CD4(+) T cells is lower. In fact, even though it is likely that there are very few, if any, IFNgamma(+) CD4(+) T cells present in the single T cell model, granuloma integrity is not influenced, indicating that high levels of IFNgamma are not required for granuloma maintenance. These data underline the importance of early CD4(+) T cell recruitment into the granuloma to anti-mycobacterial protection and show that CD4(+) T cell levels required for granuloma formation and optimal protection are different. These data also show that T cell repertoire complexity contributes to protection against mycobacteria.     

Clinical sequencing: From raw data to diagnosis with lifetime value

High‐throughput sequencing (HTS) has revolutionized genetics by enabling the detection of sequence variants at hitherto unprecedented large scale. Despite these advances, however, there are still remaining challenges in the complete coverage of targeted regions (genes, exome or genome) as well as in HTS data analysis and interpretation. Moreover, it is easy to get overwhelmed by the plethora of available methods and tools for HTS. Here, we review the step‐by‐step process from the generation of sequence data to molecular diagnosis of Mendelian diseases. Highlighting advantages and limitations, this review addresses the current state of (1) HTS technologies, considering targeted, whole‐exome, and whole‐genome sequencing on short‐ and long‐read platforms; (2) read alignment, variant calling and interpretation; as well as (3) regulatory issues related to genetic counseling, reimbursement, and data storage.     

Infection with Mycobacterium bovis BCG diverts traffic of myelin oligodendroglial glycoprotein autoantigen-specific T cells away from the central nervous system and ameliorates experimental autoimmune encephalomyelitis

Infectious agents have been proposed to influence susceptibility to autoimmune diseases such as multiple sclerosis. We induced a Th1-mediated central nervous system (CNS) autoimmune disease, experimental autoimmune encephalomyelitis (EAE) in mice with an ongoing infection with Mycobacterium bovis strain bacillus Calmette-Guérin (BCG) to study this possibility. C57BL/6 mice infected with live BCG for 6 weeks were immunized with myelin oligodendroglial glycoprotein peptide (MOG(35-55)) to induce EAE. The clinical severity of EAE was reduced in BCG-infected mice in a BCG dose-dependent manner. Inflammatory-cell infiltration and demyelination of the spinal cord were significantly lessened in BCG-infected animals compared with uninfected EAE controls. ELISPOT and gamma interferon intracellular cytokine analysis of the frequency of antigen-specific CD4(+) T cells in the CNS and in BCG-induced granulomas and adoptive transfer of MOG(35-55)-specific green fluorescent protein-expressing cells into BCG-infected animals indicated that nervous tissue-specific (MOG(35-55)) CD4(+) T cells accumulate in the BCG-induced granuloma sites. These data suggest a novel mechanism for infection-mediated modulation of autoimmunity. We demonstrate that redirected trafficking of activated CNS antigen-specific CD4(+) T cells to local inflammatory sites induced by BCG infection modulates the initiation and progression of a Th1-mediated CNS autoimmune disease.     

DNA sequence variants in the metabotropic glutamate receptor 3 and risk to schizophrenia: an association study

OBJECTIVES: Recent studies investigating the association of DNA variants in the metabotropic glutamate receptor gene (GRM3) with schizophrenia susceptibility revealed conflicting results. In this study, we focused on DNA sequence variants, for which association was reported and attempted to replicate association with schizophrenia or with cognitive deficits known to be present in patients with schizophrenia. METHODS: A sample of 242 families with affected offspring and five single nucleotide markers located in the genomic region of GRM3 has been used to replicate association with schizophrenia. In addition, results of neuropsychological tests, trail making test B and the Stroop color-naming task were available for a subgroup of these families (N=88) and an independent sample of 148 patients with schizophrenia. Correlation of these measurements with genotypic data was performed using analysis of variance. RESULTS: No statistical evidence for association with schizophrenia or correlation with cognitive deficits as measured by the trail making test B or the Stroop color-naming task and the five DNA sequence variants could be detected. A trend towards association with schizophrenia was revealed for a single marker (rs2237562, P=0.056) and for 2-marker and 3-marker haplotypes containing this variant. CONCLUSIONS: Our study of DNA sequence variants in the GRM3 gene did not provide further support for genetic association with schizophrenia or for correlation with cognitive deficits.