Taking time to feel our body: Steady increases in heartbeat perception accuracy and decreases in alexithymia over 9 months of contemplative mental training

The ability to accurately perceive signals from the body has been shown to be important for physical and psychological health as well as understanding one's emotions. Despite the importance of this skill, often indexed by heartbeat perception accuracy (HBPa), little is known about its malleability. Here, we investigated whether contemplative mental practice can increase HBPa. In the context of a 9‐month mental training study, the ReSource Project, two matched cohorts (n = 77 and n = 79) underwent three training modules of 3 months' duration that targeted attentional and interoceptive abilities (Presence module), socio‐affective (Affect module), and socio‐cognitive (Perspective module) abilities. A third cohort (n = 78) underwent 3 months of practice (Affect module) and a retest control group (n = 84) did not undergo any training. HBPa was measured with a heartbeat tracking task before and after each training module. Emotional awareness was measured by the Toronto Alexithymia Scale (TAS). Participants with TAS scores > 60 at screening were excluded. HBPa was found to increase steadily over the training, with significant and small‐ to medium‐sized effects emerging after 6 months (Cohen's d = .173) and 9 months (d = .273) of mental training. Changes in HBPa were concomitant with and predictive of changes in emotional awareness. Our results suggest that HBPa can indeed be trained through intensive contemplative practice. The effect takes longer than the 8 weeks of typical mindfulness courses to reach meaningful magnitude. These increments in interoceptive accuracy and the related improvements in emotional awareness point to opportunities for improving physical and psychological health through contemplative mental training.     

Rationale and design of a prospective study of the clinical significance of atrial arrhythmias detected by implanted device diagnostics: The TRENDS study

Background: Sustained atrial fibrillation (AF) is a common risk factor for stroke. While intermittent AF also appears to pose a substantial stroke risk, the quantitative relationship between the percentage of time spent in AF and stroke risk is poorly specified and “intermittent” AF is not the same as paroxysmal AF. Improved assessment of the impact of AF burden on stroke risk will allow more targeted and safer use of antithrombotic therapy. Methods and Results: The primary objective of this study is to determine if AT/AF (all device detected atrial tachyarrhythmias, including atrial flutter, atrial fibrillation, and atrial tachycardia) burden over a 30 day period is an independent predictor of the occurrence of ischemic stroke, transient ischemic attack (TIA) and/or systemic embolism in subjects not receiving anticoagulation therapy. TRENDS is a prospective, post-market, non-randomized, multicenter study designed to enroll 3100 subjects who have an independent Class I/II indication for cardiac rhythm device implantation and who have demographic features suggestive of an increased risk for thromboembolic complications related to AT/AF. All implanted devices will have the ability to collect long-term AT/AF burden trending data and will be equivalently programmed to ensure consistent data collection. All subjects will be followed with device interrogations every 3 months and clinic visits every 6 months for 1 year. Subjects with a documented history of AT/AF prior to enrollment and those who develop AT/AF during the 12-month follow-up will be followed until the last subject enrolled in the study has completed their 24-month follow-up. Conclusions: The results of the TRENDS study should help clarify the implications of data retrieved from an implantable device with regard to the risk for thromboembolic complications from atrial arrhythmias, even in the absence of symptoms.     

Saccharomyces cerevisiae Gcs1 is an ADP-ribosylation factor GTPase-activating protein.

Movement of material between intracellular compartments takes place through the production of transport vesicles derived from donor membranes. Vesicle budding that results from the interaction of cytoplasmic coat proteins (coatomer and clathrin) with intracellular organelles requires a type of GTP-binding protein termed ADP-ribosylation factor (ARF). The GTPase cycle of ARF proteins that allows the uncoating and fusion of a transport vesicle with a target membrane is mediated by ARF-dependent GTPase-activating proteins (GAPs). A previously identified yeast protein, Gcs1, exhibits structural similarity to a mammalian protein with ARF-GAP activity in vitro. We show herein that the Gcs1 protein also has ARF-GAP activity in vitro using two yeast Arf proteins as substrates. Furthermore, Gcs1 function is needed for the efficient secretion of invertase, as expected for a component of vesicle transport. The in vivo role of Gcs1 as an ARF GAP is substantiated by genetic interactions between mutations in the ARF1/ARF2 redundant pair of yeast ARF genes and a gcs1-null mutation; cells lacking both Gcs1 and Arf1 proteins are markedly impaired for growth compared with cells missing either protein. Moreover, cells with decreased levels of Arf1 or Arf2 protein, and thus with decreased levels of GTP-Arf, are markedly inhibited for growth by increased GCS1 gene dosage, presumably because increased levels of Gcs1 GAP activity further decrease GTP-Arf levels. Thus by both in vitro and in vivo criteria, Gcs1 is a yeast ARF GAP.     

Measurement of parathyroid hormone

Interpretation of serum immunoreactive PTH measurements requires an understanding of the secretion, metabolism, and heterogeneity of circulating immunoreactive PTH. Both intact hormone and biologically inactive carboxyl fragments containing the middle and C-terminal regions are secreted by the parathyroid glands. Inactive fragments also are produced peripherally by metabolism of intact hormone by liver and kidney. Inactive fragments represent 75 to 95% of the total immunoreactivity in serum, a consequence of their long half-life in vivo as compared with intact hormone. Immunoassays for PTH can be divided into those measuring intact hormone (N-terminal, intact) and those measuring both inactive fragments and intact hormone (mid-region, C-terminal, polyvalent). The latter principally measures inactive fragments because of their greater concentration as compared with intact hormone in peripheral serum. The clinical utility of PTH assays varies considerably because of differences in their specificity and sensitivity. Serum PTH levels have been more often observed to be elevated in individuals with primary hyperparathyroidism with the use of research quality radioimmunoassays that recognize both inactive fragments and intact hormone than with conventional N-terminal or intact assays. Homologous mid-region assays have provided exceptional clinical sensitivity in confirming primary hyperparathyroidism. Comparison of a sensitive mid-region radioimmunoassay with a recently developed two-site, noncompetitive chemiluminescent immunoassay for intact PTH indicated that both methods were highly useful in the differential diagnosis of hypercalcemia. The mid-region assay provided the best diagnostic sensitivity in primary hyperparathyroidism with more elevated levels of PTH. The sensitivity of the intact assay was good, a significant improvement over conventional N-terminal and intact assays. The specificity of the intact assay was clearly superior, with measured PTH levels found to be suppressed to below normal in most subjects with hypercalcemia associated with malignancy. In contrast, measured levels were primarily normal with the mid-region assay. The higher levels of immunoreactive PTH observed in nonparathyroid hypercalcemia with the mid-region assay are in agreement with the measurement of biologically inactive carboxyl fragments, which continue to be secreted in hypercalcemia.     

Key bioactive reaction products of the NO/H2S interaction are S/N-hybrid species,polysulfides, and nitroxyl

Experimental evidence suggests that nitric oxide (NO) and hydrogen sulfide (H₂S) signaling pathways are intimately intertwined, with mutual attenuation or potentiation of biological responses in the cardiovascular system and elsewhere. The chemical basis of this interaction is elusive. Moreover, polysulfides recently emerged as potential mediators of H₂S/sulfide signaling, but their biosynthesis and relationship to NO remain enigmatic. We sought to characterize the nature, chemical biology, and bioactivity of key reaction products formed in the NO/sulfide system. At physiological pH, we find that NO and sulfide form a network of cascading chemical reactions that generate radical intermediates as well as anionic and uncharged solutes, with accumulation of three major products: nitrosopersulfide (SSNO⁻), polysulfides, and dinitrososulfite [N-nitrosohydroxylamine-N-sulfonate (SULFI/NO)], each with a distinct chemical biology and in vitro and in vivo bioactivity. SSNO⁻ is resistant to thiols and cyanolysis, efficiently donates both sulfane sulfur and NO, and potently lowers blood pressure. Polysulfides are both intermediates and products of SSNO⁻ synthesis/decomposition, and they also decrease blood pressure and enhance arterial compliance. SULFI/NO is a weak combined NO/nitroxyl donor that releases mainly N₂O on decomposition; although it affects blood pressure only mildly, it markedly increases cardiac contractility, and formation of its precursor sulfite likely contributes to NO scavenging. Our results unveil an unexpectedly rich network of coupled chemical reactions between NO and H₂S/sulfide, suggesting that the bioactivity of either transmitter is governed by concomitant formation of polysulfides and anionic S/N-hybrid species. This conceptual framework would seem to offer ample opportunities for the modulation of fundamental biological processes governed by redox switching and sulfur trafficking.Nitrogen and sulfur are essential for all known forms of life on Earth. Our planet’s earliest atmosphere is likely to have contained only traces of O₂ but rather large amounts of hydrogen sulfide (H₂S) (1). Indeed, sulfide may have supported life long before the emergence of O₂ and NO (2, 3).^* This notion is consistent with a number of observations: H₂S is essential for efficient abiotic amino acid generation as evidenced by the recent reanalysis of samples of Stanley Miller’s original spark discharge experiments (4), sulfide is an efficient reductant in protometabolic reactions forming RNA, protein, and lipid precursors (5), and sulfide is both a bacterial and mitochondrial substrate (6), enabling even multicellular lifeforms to exist and reproduce under conditions of permanent anoxia (7). Thus, although eukaryotic cells may have originated from the symbiosis of sulfur-reducing and -oxidizing lifeforms within a self-contained sulfur redox metabolome (8), sulfide may have been essential even earlier by providing the basic building blocks of life.The chemical reactions of sulfur-centered nucleophiles with a range of nitrogen-containing species have been studied for different reasons and as independent processes for more than a century, and early reports indicated complex reaction mechanisms (9–13). The recent surge of interest in this chemistry in the biological community (13–15) was triggered by a growing appreciation that NO and sulfide exert similar and often interdependent biological actions within the cardiovascular system and elsewhere (NO/H₂S “cross-talk”) (16, 17), resulting in mutual attenuation or potentiation of their responses. This cross-talk is possibly mediated by chemical interactions (18–20), but much of the older chemical work seems to have been forgotten. Recently, low concentrations of sulfide were shown to quench NO-mediated vascular responses through formation of an uncharacterized “nitrosothiol” (RSNO) (18–20), assumed to be thionitrous acid (HSNO) (13–15).A recent report of the detection by MS of the highly unstable HSNO at physiological pH (21) has attracted considerable attention from the biological community, because it could be an intermediate in the reaction of sulfide with RSNOs (22) and a precursor for NO, nitrosonium (NO⁺) equivalents, and nitroxyl (HNO). However, a key aspect of HSNO’s properties that seems to have been overlooked in these discussions is its mobile hydrogen, allowing facile 1,3 hydrogen shift and formation of four isomers with the same chemical equation (13)—a feature described in the seminal studies by Goehring in the 1950s (23) and by Müller and Nonella later on (24, 25) that distinguishes HSNO from all other RSNOs (26). The same feature also contributes to the short half-life of the molecule at ambient temperatures, making it more probable that other yet unknown entities are involved as biological mediators of the NO/H₂S cross-talk. Chemical studies by Seel and Wagner (9, 10) showed that NO readily reacts with HS⁻ in basic aqueous solution or organic solvents under anoxic conditions to form the yellow nitrosopersulfide (SSNO⁻). Accumulation of this product was also observed after reaction of RSNOs with sulfide at pH 7.4 (26, 27); moreover, SSNO⁻-containing mixtures were found to release NO, activate soluble guanylyl cyclase (sGC) (26), and relax vascular tissue (28), although a contribution of other reaction products to these effects cannot be excluded. Meanwhile, other sulfane sulfur molecules, including persulfides (RSSH) and polysulfides (RSS_n⁻ and HS_n⁻), have come to the fore as potential mediators of sulfide’s biological effects (29–31), but little is known about their pathways of formation, prevalence in biological systems, and relationship with NO.In view of this confusion, we sought to carry out an integrative chemical/pharmacological investigation to study the chemical biology of the reaction of NO with sulfide more thoroughly and systematically identify potentially bioactive reaction products. We here report that the NO/H₂S interaction leads to formation of at least three product classes with distinct in vivo bioactivity profiles: nitrosopersulfide (SSNO⁻), polysulfides (HS_n⁻), and dinitrososulfite [ONN(OH)SO₃⁻ or N-nitrosohydroxylamine-N-sulfonate (SULFI/NO)]; all anions at physiological pH. Their formation is accompanied by both scavenging and release of NO and H₂S and formation of nitrous oxide (N₂O), nitroxyl (HNO), nitrite (NO₂⁻), nitrate (NO₃⁻), and various sulfoxy species. These results not only offer an intriguing explanation for the quenching and potentiating effects of sulfide on NO bioavailability but also, provide a novel framework for modulation of fundamental biological processes governed by redox switching and sulfur trafficking. This chemistry is likely to prevail wherever NO and sulfide are cogenerated.