Low incidence of arrhythmic syncope and pacemaker implantation in older patients with bifascicular block and implantable cardiac monitor

BACKGROUND

In patients with unexplained syncope, bifascicular block (BFB) is considered associated with syncope due to either heart block or sinus arrest. Immediate or delayed pacemaker (PM) implantation after ECG documentation of syncopal recurrence by means of implantable cardiac monitors (ICM) is still debated. We aimed to assess the incidence of recurrent syncope and guideline-based PM implantation in patients with syncope and BFB implanted with ICM.

METHODS

Consecutive patients with syncope and BFB followed at two tertiary care syncope units and implanted with ICM from 2012 to 2020 were retrospectively reviewed. Only patients with ≥2 clinical visits and ≥ 18 years of age were included. Incidence of a Class I indication for PM implantation was the primary outcome.

RESULTS

Of 635 syncope patients implanted with an ICM, 55 (8.7%) had a BFB and were included. Median age at implantation was 75 [interquartile range, IQR:64-81] years, and 28(49.1%) were women. At 26 [IQR:12-41] months follow-up, 20 (36.3%,16.3%/year) patients experienced syncope: in 6(10.9%) patients syncope was classified 'arrhythmic' with a higher prevalence in older individuals (p = 0.048). PM implantation (N = 14,25.5%) was more frequent in patients ≥75 years (p = 0.024). At survival analysis, patients ≥75 years were at highest risk of arrhythmic syncope and guideline directed PM implantation (Hazard Ratio: 4.5, 95% Confidence Intervals 1.5-13.3).

CONCLUSIONS

Most older patients with syncope who received an ICM did not have events during follow-up. One-in-three experienced syncope, and an even smaller number had an arrhythmic syncope with indication for PM implantation. Older age was strongly associated with PM implantation.

Characterization, identification and expression profiling of genome-wide R-genes in melon and their putative roles in bacterial fruit blotch resistance

Background

Bacterial fruit blotch (BFB), a disease caused by Acidovorax citrulli, results in significant economic losses in melon. The causal QTLs and genes for resistance to this disease have yet to be identified. Resistance (R)-genes play vital roles in resistance to plant diseases. Since the complete genome sequence of melon is available and genome-wide identification of R-genes has been performed for this important crop, comprehensive expression profiling may lead to the identification of putative candidate genes that function in the response to BFB.

Results

We identified melon accessions that are resistant and susceptible to BFB through repeated bioassays and characterized all 70 R-genes in melon, including their gene structures, chromosomal locations, domain organizations, motif distributions, and syntenic relationships. Several disease resistance-related domains were identified, including NBS, TIR, LRR, CC, RLK, and DUF domains, and the genes were categorized based on the domains of their encoded proteins. In addition, we profiled the expression patterns of the genes in melon accessions with contrasting levels of BFB resistance at 12 h, 1 d, 3 d, and 6 d after inoculation with A. citrulli. Six R-genes exhibited consistent expression patterns (MELO3C023441, MELO3C016529, MELO3C022157, MELO3C022146, MELO3C025518, and MELO3C004303), with higher expression levels in the resistant vs. susceptible accession.

Conclusion

We identified six putative candidate R-genes against BFB in melon. Upon functional validation, these genes could be targeted for manipulation via breeding and biotechnological approaches to improve BFB resistance in melon in the future.

Development of Molecular Marker Linked with Bacterial Fruit Blotch Resistance in Melon (Cucumis melo L.)

Bacterial fruit blotch (BFB) causes losses in melon marketable yield. However, until now, there has been no information about the genetic loci responsible for resistance to the disease or their pattern of inheritance. We determined the inheritance pattern of BFB resistance from a segregating population of 491 F₂ individuals raised by crossing BFB-resistant (PI 353814) and susceptible (PI 614596) parental accessions. All F₁ plants were resistant to Acidovorax citrulli strain KACC18782, and F₂ plants segregated with a 3:1 ratio for resistant and susceptible phenotypes, respectively, in a seedling bioassay experiment, indicating that BFB resistance is controlled by a monogenic dominant gene. In an investigation of 57 putative disease-resistance related genes across the melon genome, only the MELO3C022157 gene (encoding TIR-NBS-LRR domain), showing polymorphism between resistant and susceptible parents, revealed as a good candidate for further investigation. Cloning, sequencing and quantitative RT-PCR expression of the polymorphic gene MELO3C022157 located on chromosome 9 revealed multiple insertion/deletions (InDels) and single nucleotide polymorphisms (SNPs), of which the SNP A²⁰³⁵T in the second exon of the gene caused loss of the LRR domain and truncated protein in the susceptible accession. The InDel marker MB157-2, based on the large (504 bp) insertion in the first intron of the susceptible accession, was able to distinguish resistant and susceptible accessions among 491 F₂ and 22 landraces/inbred accessions with 98.17% and 100% detection accuracy, respectively. This novel PCR-based, co-dominant InDel marker represents a practical tool for marker-assisted breeding aimed at developing BFB-resistant melon accessions.

First Isolation and Molecular Characterization of Bacteriophages Infecting Acidovorax citrulli, the Causal Agent of Bacterial Fruit Blotch

Bacteriophages of Acidovorax citrulli, the causal agent of bacterial fruit blotch, were isolated from 39 watermelon, pumpkin, and cucumber leaf samples collected from various regions of Korea and tested against 18 A. citrulli strains. Among the six phages isolated, ACP17 forms the largest plaque, and exhibits the morphology of phages in the Myoviridae family with a head diameter of 100 ± 5 nm and tail length of 150 ± 5 nm. ACP17 has eclipse and latent periods of 25 ± 5 min and 50 ± 5 min, respectively, and a burst size of 120. The genome of ACP17 is 156,281 base pairs with a G + C content of 58.7%, 263 open reading frames, and 4 transfer RNA genes. Blast search and phylogenetic analysis of the major capsid protein showed that ACP17 has limited homology to two Stentrophomonas phages, suggesting that ACP17 is a new type of Myoviridae isolated from A. citrulli.

Fluid bed gasification--plasma converter process generating energy from solid waste: experimental assessment of sulphur species

Often perceived as a Cinderella material, there is growing appreciation for solid waste as a renewable content thermal process feed. Nonetheless, research on solid waste gasification and sulphur mechanisms in particular is lacking. This paper presents results from two related experiments on a novel two stage gasification process, at demonstration scale, using a sulphur-enriched wood pellet feed. Notable SO2 and relatively low COS levels (before gas cleaning) were interesting features of the trials, and not normally expected under reducing gasification conditions. Analysis suggests that localised oxygen rich regions within the fluid bed played a role in SO2's generation. The response of COS to sulphur in the feed was quite prompt, whereas SO2 was more delayed. It is proposed that the bed material sequestered sulphur from the feed, later aiding SO2 generation. The more reducing gas phase regions above the bed would have facilitated COS--hence its faster response. These results provide a useful insight, with further analysis on a suite of performed experiments underway, along with thermodynamic modelling.

Systemic administration and local microinjection into the central nervous system of the 5-HT(7) receptor agonist LP-211 modify the sleep-wake cycle in the rat

The effects of LP-211, a selective serotonin 5-HT7 receptor agonist were studied in adult rats implanted for chronic sleep recordings. Intraperitoneal administration of LP-211 (2.5-10mg/kg) during the light phase of the light-dark cycle significantly increased wakefulness (W) and reduced rapid-eye-movement sleep (REMS) and the number of REM periods during the 6-h recording period. Direct infusion of LP-211 into the dorsal raphe nucleus (DRN) (2-6 mM), locus coeruleus nucleus (LC) (4 mM), basal forebrain (horizontal limb of the diagonal band of Broca) (HDB) (2 mM) or laterodorsal tegmental nucleus (LDT) (4 mM) induced also a decrease of REMS. Additionally, microinjection of the 5-HT7 receptor ligand into the HDB (2 mM) augmented W. Presently, there is no satisfactory explanation for the effect of 5-HT7 receptor activation on W and REMS occurrence. Additional studies are required to characterize the neurotransmitter systems responsible for the actions of LP-211 on the behavioral states.