Effects of Apparent Temperature on the Incidence of Ventricular Tachyarrhythmias in Patients With an Implantable Cardioverter-Defibrillator: Differential Association Between Patients With and Without Electrical Storm

Background: Electrical storm (ES) has profound psychological effects and is associated with a higher mortality in patients with implantable cardioverter–defibrillator (ICD). Assessing the incidence and features of ES, is vital. Previous studies have shown winter peaks for ventricular tachyarrhythmia (VTA) in ICD patients. However, the effects of heat with a high relative humidity remain unclear. Thus, this study aimed to assess the nonlinear and lagged effects of apparent temperature [or heat index (HI)] on VTA among patients with and without ES after ICD implantation.

Methods: Of 626 consecutive patients who had ICDs implanted from January 2004 to June 2017 at our hospital, 172 who experienced sustained VTAs in ICD recording were analyzed, and their clinical records were abstracted to assess the association between VTA incidence and HI by time-stratified case-crossover analysis. Cubic splines were used for the nonlinear effect of HI, with adjustment for air pollutant concentrations.

Results: A significant seasonal effect for ES patients was noted. Apparent temperature, but not ambient temperature, was associated with VTA occurrences. The low and high HI thresholds for VTA incidence were <15° and >30°C, respectively, with a percentage change in odds ratios of 1.06 and 0.37, respectively, per 1°C. Lagged effects could only be demonstrated in ES patients, which lasted longer for low HI (in the next 4 days) than high HI (in the next 1 day).

Conclusion: VTA occurrence in ICD patients was strongly associated with low HI and moderately associated with high HI. Lagged effects of HI on VTA were noted in patients with ES. Furthermore, patients with ES were more vulnerable to heat stress than those without ES. Patients with ICD implantation, particularly in those with ES, should avoid exposure to low and high HI to reduce the risk of VTAs, improve quality of life and possibly reduce mortality.

Expression of capsid [correction of caspid] protein VP1 for use as antigen for the diagnosis of enterovirus 71 infection

To produce enterovirus 71 antigen for diagnostic purposes, the gene encoding the entire capsid protein VP1 was amplified by reverse transcription-polymerase chain reaction (RT-PCR), cloned and expressed in Escherichia coli as a poly-histidine fusion protein. Western blotting experiments with sera from patients with enterovirus 71 infection indicated that immunoglobulin G (IgG) and IgM antibodies bound to a single polypeptide VP1. According to these results, IgM anti-VP1 appeared in sera of patients with a symptomatic enterovirus 71 acute infection, whereas IgG anti-VP1 was present in sera of past infection. This finding suggests that detecting IgG and IgM immune responses against linear epitopes of recombinant VP1 is an effective means of determining the different phases of enterovirus 71 infection. In addition, sera containing coxsackie virus 16 (CA16) antibodies did not cross-react with the recombinant VP1 of enterovirus 71, despite the homology between VP1 proteins of both viruses. Comparison with reference PCR and neutralization assays showed these antibody tests to be appropriate for the serodiagnosis of enterovirus 71 infection.

Brain-derived neurotrophic factor enhances association of protein tyrosine phosphatase PTP1D with the NMDA receptor subunit NR2B in the cortical postsynaptic density

Our recent studies revealed that brain-derived neurotrophic factor (BDNF) rapidly enhances tyrosine phosphorylation and dephosphorylation of the NMDA receptor subunit, NR2B, in the postsynaptic density (PSD), potentially regulating synaptic plasticity. To explore the molecular mechanisms underlying synaptic NR2B signaling, we examined the protein tyrosine phosphatase, PTP1D; BDNF reportedly increases association of PTP1D with tyrosine phosphorylated proteins in cortical neurons and PC 12 cells. We now report that PTP1D is an intrinsic component of the rat cerebrocortical PSD, based on Western blot analysis using specific anti-PTP1D antibodies. In addition, NR2B was co-immunoprecipitated with PTP1D using anti-NR2B antibodies or anti-PTP1D antibodies, indicating physical association of the subunit with PTP1D. Moreover, treatment of the purified PSD with BDNF for 5 min elicited a two-fold increase in the association of NR2B with PTP1D. The BDNF action appeared to be specific, since nerve growth factor, another member of the neurotrophin gene family, did not alter the association. Finally, an overlay assay revealed that BDNF caused a two-fold increase in binding of blotted PSD NR2B proteins to PTP1D-SH2 domains, revealing molecular mechanisms mediating the PTP1D-NR2B binding. Taken together, our results raise the possibility that PTP1D participates in BDNF-mediated NR2B signaling cascades at the postsynaptic site, thereby regulating synaptic plasticity.

Florid osseous dysplasia: case report

Florid osseous dysplasia (FOD) is a benign, non-neoplastic lesion characterized by multiple sclerosing masses only within the jawbones. It is most prevalent in middle-aged black women but uncommon in Orientals. Most cases are asymptomatic and should be left untreated. However, the jawbone involved in FOD is very susceptible to infection, including osteomyelitis developed from periodontitis, pulpopathosis, bone biopsy, wearing removable partial dentures, root canal therapy, tooth extraction, inappropriate dental treatment, etc. If secondary osteomyelitis develops, antibiotic and conservative dental therapy treatment is recommended for removing the sources of the odontogenic infection. Surgical removal of inflamed masses is indicated if the inflammatory signs and symptoms are persistent after antibiotic and conservative dental therapy. Here we report a rare FOD case in which an osteomyelitis resulting from generalized periodontitis and bone biopsy was triggered. The patient was accepted for surgery and follow-up in our department. The current literature of this disease is reviewed as well, focusing especially on the clinical manifestations, radiographic features, differential diagnosis, and treatment.

A novel spliced transcript of influenza A/WSN/33 virus

It has been shown that influenza A virus M1 mRNA has two alternative 5" splice sites: a distal 5" splice site producing M3 mRNA that has the coding potential for 9 amino acids and a proximal 5" splice site producing M2 mRNA that encodes the essential M2 ion-channel protein. In this study, we demonstrated that the laboratory widely used strain A/WSN/33, but not A/Udorn/72 possessed another novel 5" splice site producing a transcript with the coding potential for 54 amino acids. We nominated this novel transcript as M4 mRNA. M4 mRNA was detected in A/WSN/33-infected cells derived from different species. Sequence comparison of M1 mRNA in both A/WSN/33 and Udorn/72 at position 143 to 151 reveals that this novel 5" splice site generated in WSN was due to one nucleotide difference at position 147. Several strains of influenza A viruses other than WSN also possess the potential M4 5" splice site by sequence analysis from the files of GenBank.

NMDA receptor subunits in the postsynaptic density of rat brain: expression and phosphorylation by endogenous protein kinases

N-methyl-D-aspartate (NMDA) receptors (NRs) play critical roles in diverse synaptic processes in the brain. However, subcellular distribution, spatiotemporal expression and regulation of NR subunits in brain synapses are unknown. We report that NR1 and NR2A-2C subunits are all enriched in the postsynaptic density (PSD), which plays critical roles in trophin-mediated synaptic plasticity. Significant expression of NRs was observed the first two weeks after birth, during synaptogenesis, and in adulthood. Functional diversity of NRs, resulting from heterogeneous composition, was supported by the finding that different NR2 subunits were associated in a region-specific manner with NR1. Phosphorylation of NR1, a key subunit of the NMDA receptor-channel complex, was significantly enhanced by activators of calmodulin (CaM) kinases (CKs) or protein kinase C (PKC), but not by those of PKA. Co-immunoprecipitation studies revealed that NR1 was physically associated with functionally active PKCgamma and the major PSD protein (mPSDp) through noncovalent interactions. Our results suggest that NMDA receptors play roles in postsynaptic mechanisms in a subunit-, composition-, brain region- and developmental-specific manner. Our findings also indicate that the PSD is a coherent functional unit containing protein kinases that potentially regulate NMDA receptor function via phosphorylation.

BDNF acutely increases tyrosine phosphorylation of the NMDA receptor subunit 2B in cortical and hippocampal postsynaptic densities

While neurotrophins are critical for neuronal survival and differentiation, recent work suggests that they acutely regulate synaptic transmission as well. Brain-derived neurotrophic factor (BDNF) enhances excitatory postsynaptic currents in cultured dissociated hippocampal neurons within 2-3 min through postsynaptic, phosphorylation-dependent mechanisms. Moreover, BDNF modulates hippocampal long-term potentiation, in which postsynaptic NMDA (N-methyl-D-aspartate) receptors (NRs) play a key role. We now report that BDNF acutely increases tyrosine phosphorylation of the specific NMDA receptor subunit NR2B, which has recently been shown to play a role in long-term potentiation. Incubation of BDNF with cortical or hippocampal postsynaptic densities for 5 min increased tyrosine phosphorylation of the NR2B subunits in a dose-dependent manner. A maximal increase to 165% of control phosphorylation occurred at a BDNF concentration of 2 ng/ml. The BDNF action appeared to be specific, since nerve growth factor, another member of the neurotrophin gene family, had no effect on NR2B phosphorylation. Further, BDNF action was selective, since it did not alter tyrosine phosphorylation of NR2A subunits. Our results suggest that tyrosine phosphorylation of NR2B subunits of the NMDA receptor may contribute to neurotrophin modulation of postsynaptic responsiveness and long-term potentiation.

Brain-derived neurotrophic factor rapidly enhances phosphorylation of the postsynaptic N-methyl-D-aspartate receptor subunit 1

Although neurotrophins have traditionally been regarded as neuronal survival factors, recent work has suggested a role for these factors in synaptic plasticity. In particular, brain-derived neurotrophic factor (BDNF) rapidly enhances synaptic transmission in hippocampal neurons through trkB receptor stimulation and postsynaptic phosphorylation mechanisms. Activation of trkB also modulates hippocampal long-term potentiation, in which postsynaptic N-methyl-D-aspartate glutamate receptors play a key role. However, the final common pathway through which BDNF increases postsynaptic responsiveness is unknown. We now report that BDNF, within 5 min of exposure, elicits a dose-dependent increase in phosphorylation of the N-methyl-D-aspartate receptor subunit 1. This acute effect occurred in hippocampal synaptoneurosomes, which contain pre- and postsynaptic elements, and in isolated hippocampal postsynaptic densities. Nerve growth factor, in contrast, caused no enhancement of phosphorylation. These results suggest a potential mechanism for trophin-induced potentiation of synaptic transmission.

Functional trkB neurotrophin receptors are intrinsic components of the adult brain postsynaptic density

Neurotrophins have long been thought to act as target-derived factors that regulate the survival and differentiation of afferent neurons. Recently, brain-derived neurotrophic factor (BDNF) was shown to elicit rapid increases in synaptic activity of cultured hippocampal neurons by enhancing responsiveness to excitatory input. These findings suggest a postsynaptic localization of neurotrophin receptors. In this study, we examined the expression of trkB, a high-affinity receptor for BDNF, in the postsynaptic density (PSD), a proteinaceous specialization of the postsynaptic membrane. Western blot analyses with antibodies to trkB revealed localization to the PSD in adult rat cerebral cortex and hippocampus. Only the full-length, active form of trkB was detected in PSD samples. BDNF treatment of the adult cortical PSD resulted in a 5-fold increase in trkB autophosphorylation, supporting the contention that the PSD contains functional trkB. Truncated trkB, which does not contain the tyrosine kinase signaling domain, though present in membrane fractions, was undetectable in the PSD. The presence of trkB in the PSD is consistent with a role for neurotrophins in the regulation of synaptic activity via direct postsynaptic mechanisms.

Nitric oxide increases calcium/calmodulin-dependent phosphorylation of proteins in the postsynaptic density of adult rat cerebral cortex

Nitric oxide (NO) plays important roles in diverse processes, including neurotransmission in the peripheral and central nervous systems. Nitric oxide synthase (NOS), the enzyme that catalyzes formation of NO from L-arginine, is an intrinsic component of the postsynaptic density (PSD), a specialization of the postsynaptic membrane. This raises the possibility that NO may play a role in postsynaptic function. To begin defining postsynaptic actions of NO, we examined effects of NO on Ca2+/calmodulin-dependent phosphorylation (C/C-DP) of proteins in the cortical PSD of adult rat brain. Treatment of the PSD with sodium nitroprusside, a NO donor, caused a 4-fold increase in C/C-DP of the major PSD protein (mPSDp), relative to C/C treatment alone. Another NO donor, S,S'-dinitrosodithiol, elicited a 2-fold increase in C/C-DP of the mPSDp. Treatment of PSD fractions with L-arginine, a substrate for endogenous NOS, caused a 3-fold increase in C/C-DP activity. The competitive NOS inhibitor, N-L-arginine-methyl ester, decreased basal C/C-DP of cortical mPSDp by 50% and blocked the increase elicited by L-arginine. The inhibitor had no effect on cAMP-dependent phosphorylation, suggesting specificity of NO action on C/C-DP. Our observations indicate that NO enhances C/C-DP of PSD proteins. As C/C-DP inactivates NOS, our findings raise the possibility that NO effects on C/C-DP constitute a feedback mechanism for regulation of NOS activity.