bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Comprehensive Algorithm for Evaluation of PICU Patients With New Fever or Instability*
Authors: Sick-Samuels Anna C. , Booth Lauren D. , Milstone Aaron M. , Schumacher Christina , Bergmann Jules , Stockwell David C.
Published: May 2023

OBJECTIVES:

There is variation in microbiology testing among PICU patients with fever offering opportunities to reduce avoidable testing and treatment. Our objective is to describe the development and assess the impact of a novel comprehensive testing algorithm to support judicious testing practices and expanded diagnostic differentials for PICU patients with new fever or instability.

DESIGN:

A mixed-methods quality improvement study.

SETTING:

Single-center academic PICU and pediatric cardiac ICU.

SUBJECTS:

Admitted PICU patients and physicians.

INTERVENTIONS:

A multidisciplinary team developed a clinical decision-support algorithm.

MEASUREMENTS AND MAIN RESULTS:

We evaluated blood, endotracheal, and urine cultures, urinalyses, and broad-spectrum antibiotic use per 1,000 ICU patient-days using statistical process control charts and incident rate ratios (IRRs) and assessed clinical outcomes 24 months pre- and 18 months postimplementation. We surveyed physicians weekly for 12 months postimplementation. Blood cultures declined by 17% (IRR, 0.83; 95% CI, 0.77–0.89), endotracheal cultures by 26% (IRR, 0.74; 95% CI, 0.63–0.86), and urine cultures by 36% (IRR, 0.64; 95% CI, 0.56–0.73). There was an anticipated rise in urinalysis testing by 23% (IRR, 1.23; 95% CI, 1.14–1.33). Despite higher acuity and fewer brief hospitalizations, mortality, hospital, and PICU readmissions were stable, and PICU length of stay declined. Of the 108 physician surveys, 46 replied (43%), and 39 (85%) recently used the algorithm; 0 reported patient safety concerns, two (4%) provided constructive feedback, and 28 (61%) reported the algorithm improved patient care.

CONCLUSIONS:

A comprehensive fever algorithm was associated with reductions in blood, endotracheal, and urine cultures and anticipated increase in urinalyses. We detected no patient harm, and physicians reported improved patient care.
Measuring Energy Requirements of Traumatic Brain Injury Patients in Pediatric Intensive Care With Indirect Calorimetry: A Comparison With Empiric Methods*
Authors: Beggs Megan R. , Ashkin Allison , Larsen Bodil M. K. , Garros Daniel
Published: May 2023

OBJECTIVES:

Energy requirements following moderate or severe pediatric traumatic brain injury (TBI) have not been fully elucidated. Indirect calorimetry (IC) is the gold standard for measuring resting energy expenditure (MREE) in PICU. However, technical complexity limits its use. We aimed to determine whether MREE differs from standard of care energy estimation and delivery in a cohort of pediatric patients following moderate to severe TBI during PICU admission.

DESIGN:

Retrospective case series study.

SETTING:

Single-center, 16-bed general PICU in Canada between May 2011 and January 2019.

PATIENTS:

Children (0–18 yr) admitted to a PICU for moderate (Glasgow Coma Scale [GCS] 9–12) to severe TBI (GCS < 9) and had an IC study performed while mechanically ventilated.

INTERVENTIONS:

None.

MEASUREMENTS AND MAIN RESULTS:

During the study period, 245 patients were admitted with the diagnosis of trauma with TBI. The study includes a convenience sample of 26 patients with severe (n = 23) and moderate (n = 3) TBI who underwent a total of 34 IC measurements. MREE varied considerably from 29% to 144% of predicted energy expenditure. Using Bland-Altman comparative analysis, neither Schofield nor World Health Organization predictive equations were in agreement with MREE. Only one measurement revealed that the patient was appropriately fed (energy provided in nutrition support was within 10% of MREE); 10 (38%) measurements revealed overfeeding and 15 (58%) underfeeding at the time of testing.

CONCLUSIONS:

The present study adds to the small body of literature highlighting the limitations of predictive equations to evaluate energy requirements following moderate to severe pediatric TBI. IC, when feasible, should be used as the preferred method to orient PICU teams to feed such vulnerable patients.
Predictors of Risk for Cerebral Palsy: A Review
Authors: Mohanty Tanochni , Joseph Sibi Daniel , Gunasekaran Pradeep Kumar , Doreswamy Srinivasa Murthy , Saini Lokesh
Published: May 2023

Purpose:

To identify the earliest predictors of risk for diagnosis of cerebral palsy (CP).

Methods:

A comprehensive literature search was conducted using various databases. The publications were reviewed to identify risk factors for CP from conception to early infancy. Studies were critically appraised with Joanna Briggs Institute guidelines for quality appraisal and evaluated for risk of bias using the Agency for Health Care Research and Quality guidelines.

Results:

The initial search yielded 129 studies and 20 studies were included. Forty-seven risk factors for CP were extracted of which several were duplicate terms. The significant risk factors found to be indicative of CP were low birth weight (<1500 g), birth at less than 28 weeks of gestational age, periventricular leukomalacia, grade 3 or 4 intraventricular hemorrhage, preeclampsia, prematurity, an Apgar score of less than 4 at the first minute, birth asphyxia, preterm premature rupture of membrane, and absent fidgety movements.

Conclusion:

Twenty-three factors were consistently reported as predictors of CP.
Early Identification of Atypical Motor Performance of Infants With Prenatal Opioid Exposure
Authors: Boynewicz Kara , Campbell Suzann K. , Chroust Alyson
Published: May 2023

Purpose:

To investigate the association between prenatal opioid exposure (POE) and newborn infants' motor performance to aid in the early identification of developmental delays.

Methods:

Nineteen infants with POE requiring pharmacological treatment, 27 infants with POE without pharmacological treatment, and 25 infants without POE were assessed via the Test of Infant Motor Performance (TIMP).

Results:

Infants in both groups with POE had lower TIMP scores than infants without POE. There was no difference between the TIMP scores of infants with POE who required pharmacological treatment and infants with POE who did not require pharmacological treatment.

Conclusions:

The TIMP can detect differences in motor performance of infants with POE. Regardless of whether infants required pharmacological treatment, POE was associated with lower motor performance. Those working in hospital or early intervention settings can use the TIMP to identify early delays in infants with POE and refer for intervention.
Ventral Column Spinal Cord Stimulation for Post Lumbar Laminectomy Syndrome: A Case Report
Authors: Van Acker Gustaf , Kim Chong H.
Published: May 2023

Spinal cord stimulation is an increasingly utilized treatment for a number of chronic pain states. Dorsal column stimulation is historically and currently the anatomical target of choice for most chronic pain conditions, including post-laminectomy syndrome and radicular pain. However early studies suggested that stimulation of an alternative target, the ventral columns that carry pain fibers in the anterior and lateral spinothalamic tracts, may offer comparable or superior pain relief. A patient undergoing standard-of-care spinal cord stimulation trial had an additional lead placed on the right ventrolateral aspect of the spinal cord. Following the usual 7-day trial of dorsal column stimulation, the dorsal leads were removed and ventrolateral column stimulation was applied through the retained ventral lead for a period of 3 days. The Brief Pain Index Short Form and Numeric Rating Scale were recorded for both dorsal and ventral stimulation. Ventrolateral spinal cord stimulation provided comparable outcomes compared with dorsal column stimulation using non-paresthesia-based stimulation. The results suggest further investigation into spinal cord stimulation anatomical placement and mechanism of action is warranted.
Artificial Intelligence to Reduce or Eliminate the Need for Gadolinium-Based Contrast Agents in Brain and Cardiac MRI
Authors: Mallio Carlo A. , Radbruch Alexander , Deike-Hofmann Katerina , van der Molen Aart J. , Dekkers Ilona A. , Zaharchuk Greg , Parizel Paul M. , Beomonte Zobel Bruno , Quattrocchi Carlo C.
Published: May 2023

Brain and cardiac MRIs are fundamental noninvasive imaging tools, which can provide important clinical information and can be performed without or with gadolinium-based contrast agents (GBCAs), depending on the clinical indication. It is currently a topic of debate whether it would be feasible to extract information such as standard gadolinium-enhanced MRI while injecting either less or no GBCAs. Artificial intelligence (AI) is a great source of innovation in medical imaging and has been explored as a method to synthesize virtual contrast MR images, potentially yielding similar diagnostic performance without the need to administer GBCAs. If possible, there would be significant benefits, including reduction of costs, acquisition time, and environmental impact with respect to conventional contrast-enhanced MRI examinations. Given its promise, we believe additional research is needed to increase the evidence to make these AI solutions feasible, reliable, and robust enough to be integrated into the clinical framework. Here, we review recent AI studies aimed at reducing or replacing gadolinium in brain and cardiac imaging while maintaining diagnostic image quality.
A Novel Method to Reconstruct the Upper and Lower Jaws Using 3D-Custom-Made Titanium Implants
Authors: Al-Sukhun Jehad
Published: May 2023

Background:

This paper presents a novel method of upper and lower jaw reconstruction using 3D-custom-made titanium implants with abutment-like projections. The implants were designed to rehabilitate the oral and facial shape, esthetic, function, and occlusion.

Patient and Method:

A 20-year-old boy was diagnosed as having Gorlin syndrome. The patient suffered from having large bony defects, after ablative multiple keratocysts resection, of the maxilla and mandible. The resulting defects were reconstructed with 3D-custom-made titanium implants. The implants with abutment-like projections were simulated, printed, and fabricated with a selective milling method based on computed tomography scan data.

Result:

There were no postoperative infections or foreign body reactions during the 1-year follow-up period.

Conclusion:

To the best of our knowledge, this is the first report on the use of 3D-custom-made titanium implants with abutment-like projections, attempting to rehabilitate the occlusion and overcome the limitations of custom-made implants in treating large bony defects of the maxilla and mandible.
The reports of my death are greatly exaggerated: An evaluation of futility cut points in massive transfusion
Authors: Clements Thomas W. , Van Gent Jan-Michael , Lubkin David E. , Wandling Michael W. , Meyer David E. , Moore Laura J. , Cotton Bryan A.
Published: May 2023

BACKGROUND

Following COVID and the subsequent blood shortage, several investigators evaluated futility cut points in massive transfusion. We hypothesized that early aggressive use of damage-control resuscitation, including whole blood (WB), would demonstrate that these cut points of futility were significantly underestimating potential survival among patients receiving >50 U of blood in the first 4 hours.

METHODS

Adult trauma patients admitted from November 2017 to October 2021 who received emergency-release blood products in prehospital or emergency department setting were included. Deaths within 30 minutes of arrival were excluded. Total blood products were defined as total red blood cell, plasma, and WB in the field and in the first 4 hours after arrival. Patients were first divided into those receiving ≤50 or >50 U of blood in the first 4 hours. We then evaluated patients by whether they received any WB or received only component therapy. Thirty-day survival was evaluated for all included patients.

RESULTS

A total of 2,299 patients met the inclusion criteria (2,043 in ≤50 U, 256 in >50 U groups). While there were no differences in age or sex, the >50 U group was more likely to sustain penetrating injury (47% vs. 30%, p < 0.05). Patients receiving >50 U of blood had lower field and arrival blood pressure and larger prehospital and emergency department resuscitation volumes (p < 0.05). Patients in the >50 U group had lower survival than those in the ≤50 cohort (31% vs. 79%; p < 0.05). Patients who received WB (n = 1,291) had 43% increased odds of survival compared with those who received only component therapy (n = 1,008) (1.09–1.87, p = 0.009) and higher 30-day survival at transfusion volumes >50 U.

CONCLUSION

Patient survival rates in patients receiving >50 U of blood in the first 4 hours of care are as high as 50% to 60%, with survival still at 15% to 25% after 100 U. While responsible blood stewardship is critical, futility should not be declared based on high transfusion volumes alone.

LEVEL OF EVIDENCE

Therapeutic/Care Management; Level III.
Exploring the characteristics of successful prehospital trauma care teams: Insights from military trauma care simulations
Authors: Mitchnik Ilan Y. , Talmy Tomer , Feldman Barak , Almog Ofer , Fogel Itay
Published: May 2023

BACKGROUND

Trauma care teams play a crucial role in determining the outcomes of trauma victims. The composition and training of these teams can vary. Our study seeks to examine the characteristics of successful military Advanced Life Support (ALS) teams and the factors that affect them.

METHODS

A retrospective study was conducted at the Israel Defense Force (IDF) Military Medical Academy throughout 2021, where prehospital medical teams were observed in trauma care simulations. Teams were led by ALS providers (military physicians or paramedics) trained in IDF Military Trauma Life Support. Demographic and training data were collected. Teams were categorized into high or subpar performance groups based on simulation scores. Specific skills were assessed by trauma instructors using a points system. Scores were compared between the groups and analyzed for correlations with demographic and training data.

RESULTS

Overall, 63 team simulations were analyzed, with teams led by a military paramedic in 78% of simulations. The mean overall simulation performance was 81% ±6.2, and there were no differences in scores of single or multicasualty simulations. A total 3% of the teams achieved successful results and were more likely to have a paramedic as the ALS provider (p = 0.028). A sensitivity analysis excluding physicians was conducted and showed that high-performance teams had significantly higher skill assessments for primary survey (p = 0.004), injury recognition (p = 0.002), exposure (p = 0.006), adherence to clinical practice guidelines (p = 0.032), and medical device use (p = 0.002).

CONCLUSION

Our study found that ALS provider is associated with overall simulation performance in prehospital ALS teams, with military paramedics more likely to be successful. These findings have implications for the training and staffing of prehospital ALS teams, suggesting that teams should be composed accordingly and that training should focus on skills affected by the ALS provider type.

LEVEL OF EVIDENCE

Prognostic and Epidemiological; Level IV.
Cardiomyocyte electrophysiology and its modulation: current views and future prospects
Authors: Huang Christopher L.-H. , Lei Ming
Published: May 2023

Normal and abnormal cardiac rhythms are of key physiological and clinical interest. This introductory article begins from Sylvio Weidmann's key historic 1950s microelectrode measurements of cardiac electrophysiological activity and Singh & Vaughan Williams's classification of cardiotropic targets. It then proceeds to introduce the insights into cardiomyocyte function and its regulation that subsequently emerged and their therapeutic implications. We recapitulate the resulting view that surface membrane electrophysiological events underlying cardiac excitation and its initiation, conduction and recovery constitute the final common path for the cellular mechanisms that impinge upon this normal or abnormal cardiac electrophysiological activity. We then consider progress in the more recently characterized successive regulatory hierarchies involving Ca2+homeostasis, excitation–contraction coupling and autonomic G-protein signalling and their often reciprocal interactions with the surface membrane events, and their circadian rhythms. Then follow accounts of longer-term upstream modulation processes involving altered channel expression, cardiomyocyte energetics and hypertrophic and fibrotic cardiac remodelling. Consideration of these developments introduces each of the articles in thisPhil. Trans. Btheme issue. The findings contained in these articles translate naturally into recent classifications of cardiac electrophysiological targets and drug actions, thereby encouraging future iterations of experimental cardiac electrophysiological discovery, and testing directed towards clinical management.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
Late sodium current in synergism with Ca
2+
/calmodulin-dependent protein kinase II contributes to β-adrenergic activation-induced atrial fibrillation
Authors: Liu Xiaoyan , Ren Lu , Yu Shandong , Li Gang , He Pengkang , Yang Qiaomei , Wei Xiaohong , Thai Phung N. , Wu Lin , Huo Yong
Published: May 2023

Atrial fibrillation (AF) is frequently associated with β-adrenergic stimulation, especially in patients with structural heart diseases. The objective of this study was to determine the synergism of late sodium current (late
I
Na
) and Ca
2+
/calmodulin-dependent protein kinase (CaMKII)-mediated arrhythmogenic activities in β-adrenergic overactivation-associated AF. Monophasic action potential, conduction properties, protein phosphorylation, ion currents and cellular trigger activities were measured from rabbit-isolated hearts, atrial tissue and atrial myocytes, respectively. Isoproterenol (ISO, 1–15 nM) increased atrial conduction inhomogeneity index, phospho-Na
v
1.5 and phospho-CaMKII protein levels and late
I
Na
by 108%, 65%, 135% and 87%, respectively, and induced triggered activities and episodes of AF in all hearts studied (
p
< 0.05). Sea anemone toxin II (ATX-II, 2 nM) was insufficient to induce any atrial arrhythmias, whereas the propensities of AF were greater in hearts treated with a combination of ATX-II and ISO. Ranolazine, eleclazine and KN-93 abolished ISO-induced AF, attenuated the phosphorylation of Na
v
1.5 and CaMKII, and reversed the increase of late
I
Na
(
p
< 0.05) in a synergistic mode. Overall, late
I
Na
in association with the activation of CaMKII potentiates β-adrenergic stimulation-induced AF and the inhibition of both late
I
Na
and CaMKII exerted synergistic anti-arrhythmic effects to suppress atrial arrhythmic activities associated with catecholaminergic activation.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
SCN5A
channelopathy: arrhythmia, cardiomyopathy, epilepsy and beyond
Authors: Remme Carol Ann
Published: May 2023

Influx of sodium ions through voltage-gated sodium channels in cardiomyocytes is essential for proper electrical conduction within the heart. Both acquired conditions associated with sodium channel dysfunction (myocardial ischaemia, heart failure) as well as inherited disorders secondary to mutations in the gene
SCN5A
encoding for the cardiac sodium channel Nav1.5 are associated with life-threatening arrhythmias. Research in the last decade has uncovered the complex nature of Nav1.5 distribution, function, in particular within distinct subcellular subdomains of cardiomyocytes. Nav1.5-based channels furthermore display previously unrecognized non-electrogenic actions and may impact on cardiac structural integrity, leading to cardiomyopathy. Moreover,
SCN5A
and Nav1.5 are expressed in cell types other than cardiomyocytes as well as various extracardiac tissues, where their functional role in, e.g. epilepsy, gastrointestinal motility, cancer and the innate immune response is increasingly investigated and recognized. This review provides an overview of these novel insights and how they deepen our mechanistic knowledge on
SCN5A
channelopathies and Nav1.5 (dys)function.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
Pro-arrhythmic effects of gain-of-function potassium channel mutations in the short QT syndrome
Authors: Hancox J. C. , Du C. Y. , Butler A. , Zhang Y. , Dempsey C. E. , Harmer S. C. , Zhang H.
Published: May 2023

The congenital short QT syndrome (SQTS) is a rare condition characterized by abbreviated rate-corrected QT (QTc) intervals on the electrocardiogram and by increased susceptibility to both atrial and ventricular arrhythmias and sudden death. Although mutations to multiple genes have been implicated in the SQTS, evidence of causality is particularly strong for the first three (SQT1−3) variants: these result from gain-of-function mutations in genes that encode K
+
channel subunits responsible, respectively, for the I
Kr
, I
Ks
and I
K1
cardiac potassium currents. This article reviews evidence for the impact of SQT1-3 missense potassium channel gene mutations on the electrophysiological properties of I
Kr
, I
Ks
and I
K1
and of the links between these changes and arrhythmia susceptibility. Data from experimental and simulation studies and future directions for research in this field are considered.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
Human atrial fibrillation and genetic defects in transient outward currents: mechanistic insights from multi-scale computational models
Authors: Alrabghi Ghadah , Liu Yizhou , Hu Wei , Hancox Jules C. , Zhang Henggui
Published: May 2023

Previous studies have linked dysfunctional
I
to
arising from mutations to
KCND3
-encoded Kv4.3 and
KCND2
-encoded Kv4.2 to atrial fibrillation. Using computational models, this study aimed to investigate the mechanisms underlying pro-arrhythmic effects of the gain-of-function Kv4.3 (T361S, A545P) and Kv4.2 (S447R) mutations. Wild-type and mutant
I
to
formulations were developed from and validated against experimental data and incorporated into the Colman
et al
. model of human atrial cells. Single-cell models were incorporated into one- (1D) and two-dimensional (2D) models of atrial tissue, and a three-dimensional (3D) realistic model of the human atria. The three gain-of-function mutations had similar, albeit quantitatively different, effects: shortening of the action potential duration; lowering the plateau membrane potential, abbreviating the effective refractory period (ERP) and the wavelength (WL) of atrial excitation at the tissue level. Restitution curves for the WL, the ERP and the conduction velocity were leftward shifted, facilitating the conduction of atrial excitation waves at high excitation rates. The mutations also increased lifespan and stationarity of re-entry in both 2D and 3D simulations, which further highlighted a mutation-induced increase in spatial dispersion of repolarization. Collectively, these changes account for pro-arrhythmic effects of these Kv4.3 and Kv4.2 mutations in facilitating AF.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
Cardiac deficiency of P21-activated kinase 1 promotes atrial arrhythmogenesis in mice following adrenergic challenge
Authors: Jung Eunjeong , Capel Rebecca , Jiang Congshan , Venturi Elisa , Neagu Georgiana , Pearcey Sarah , Zhou Yafei , Zhang Yanmin , Lei Ming
Published: May 2023

P21-activated kinase 1 (Pak1) signalling plays a vital and overall protective role in the heart. However, the phenotypes of
Pak1
deficiency in the cardiac atria have not been well explored. In this study,
Pak1
cardiac-conditional knock-out (cKO) mice were studied under baseline and adrenergic challenge conditions.
Pak1
cKO mice show atrial arrhythmias including atrial fibrillation (AF)
in vivo
, detected during anaesthetized electrocardiography without evidence of interstitial fibrosis upon Masson's trichrome staining. Optical mapping of left atrial preparations from
Pak1
cKO mice revealed a higher incidence of Ca
2+
and action potential alternans under isoprenaline challenge and differences in baseline action potential and calcium transient characteristics. Type-2 ryanodine receptor (RyR2) channels from
Pak1
cKO hearts had a higher open probability than those from wild-type. Reverse transcription-quantitative polymerase chain reaction and Western blotting indicated that pCamkII
δ
and RyR2 are highly phosphorylated at baseline in the atria of
Pak1
cKO mice, while the expression of
Slc8a2
and
Slc8a3
as a Na
+
–Ca
2+
exchanger, controlling the influx of Ca
2+
from outside of the cell and efflux of Na
+
from the cytoplasm, are augmented. Chromatin immunoprecipitation study showed that pCreb1 interacts with
Slc8a2
and
Slc8a3
. Our study thus demonstrates that deficiency of
Pak1
promotes atrial arrhythmogenesis under adrenergic stress, probably through post-translational and transcriptional modifications of key molecules that are critical to Ca
2+
homeostasis.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
Small-conductance calcium-activated potassium channels in the heart: expression, regulation and pathological implications
Authors: Liu Ting , Li Tao , Xu Dandi , Wang Yan , Zhou Yafei , Wan Juyi , Huang Christopher L.-H. , Tan Xiaoqiu
Published: May 2023

Ca
2+
-activated K
+
channels are critical to cellular Ca
2+
homeostasis and excitability; they couple intracellular Ca
2+
and membrane voltage change. Of these, the small, 4–14 pS, conductance SK channels include three,
KCNN1-3
encoded, SK1/KCa2.1, SK2/KCa2.2 and SK3/KCa2.3, channel subtypes with characteristic, EC
50
∼ 10 nM, 40 pM, 1 nM, apamin sensitivities. All SK channels, particularly SK2 channels, are expressed in atrial, ventricular and conducting system cardiomyocytes. Pharmacological and genetic modification results have suggested that SK channel block or knockout prolonged action potential durations (APDs) and effective refractory periods (ERPs) particularly in atrial, but also in ventricular, and sinoatrial, atrioventricular node and Purkinje myocytes, correspondingly affect arrhythmic tendency. Additionally, mitochondrial SK channels may decrease mitochondrial Ca
2+
overload and reactive oxygen species generation. SK channels show low voltage but marked Ca
2+
dependences (EC
50
∼ 300–500 nM) reflecting their α-subunit calmodulin (CaM) binding domains, through which they may be activated by voltage-gated or ryanodine-receptor Ca
2+
channel activity. SK function also depends upon complex trafficking and expression processes and associations with other ion channels or subunits from different SK subtypes. Atrial and ventricular clinical arrhythmogenesis may follow both increased or decreased SK expression through decreased or increased APD correspondingly accelerating and stabilizing re-entrant rotors or increasing incidences of triggered activity.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
Compartmentalized cAMP signalling and control of cardiac rhythm
Authors: Tomek Jakub , Zaccolo Manuela
Published: May 2023

In the last 30 years, the field of cyclic adenosine 3′,5′-monophosphate (cAMP) signalling has witnessed a transformative development with the realization that cAMP is compartmentalized and that spatial regulation of cAMP is critical for faithful signal propagation and hormonal specificity. This recognition has changed our understanding of cAMP signalling from the canonical model, where a linear pathway connects a plasma membrane receptor to intracellular effectors and their targets, to a model where signal transduction occurs within a complex network of alternative branches and where an individual receptor leads to activation of a limited fraction of the network, enabled by local regulation of independent signalling units, resulting in a specific functional outcome. The cardiac myocyte has served as the cell model for many of the original findings leading to this paradigm. In this review, we cover some of the evidence supporting this new perspective and discuss how this model is providing novel mechanistic insight into cardiac myocyte physiology. With a focus on the regulation of cardiac rhythm, we consider how this model can provide an original framework for the identification of disease mechanisms.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
Human induced pluripotent stem cell-derived cardiac myocytes and sympathetic neurons in disease modelling
Authors: Li Ni , Edel Michael , Liu Kun , Denning Chris , Betts Jacob , Neely Oliver C. , Li Dan , Paterson David J.
Published: May 2023

Human induced pluripotent stem cells (hiPSC) offer an unprecedented opportunity to generate model systems that facilitate a mechanistic understanding of human disease. Current differentiation protocols are capable of generating cardiac myocytes (hiPSC-CM) and sympathetic neurons (hiPSC-SN). However, the ability of hiPSC-derived neurocardiac co-culture systems to replicate the human phenotype in disease modelling is still in its infancy. Here, we adapted current methods for efficient and replicable induction of hiPSC-CM and hiPSC-SN. Expression of cell-type-specific proteins were confirmed by flow cytometry and immunofluorescence staining. The utility of healthy hiPSC-CM was tested with pressor agents to develop a model of cardiac hypertrophy. Treatment with angiotensin II (AngII) resulted in: (i) cell and nuclear enlargement, (ii) enhanced fetal gene expression, and (iii) FRET-activated cAMP responses to adrenergic stimulation. AngII or KCl increased intracellular calcium transients in hiPSC-SN. Immunostaining in neurocardiac co-cultures demonstrated anatomical innervation to myocytes, where myocyte cytosolic cAMP responses were enhanced by forskolin compared with monocultures. In conclusion, human iPSC-derived cardiac myocytes and sympathetic neurons replicated many features of the anatomy and (patho)physiology of these cells, where co-culture preparations behaved in a manner that mimicked key physiological responses seen in other mammalian systems.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
A perspective on Notch signalling in progression and arrhythmogenesis in familial hypertrophic and dilated cardiomyopathies
Authors: Langa Paulina , Shafaattalab Sanam , Goldspink Paul H. , Wolska Beata M. , Fernandes Aurelia A. , Tibbits Glen F. , Solaro R. John
Published: May 2023

In this perspective, we discussed emerging data indicating a role for Notch signalling in inherited disorders of the heart failure with focus on hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) linked to variants of genes encoding mutant proteins of the sarcomere. We recently reported an upregulation of elements in the Notch signalling cascade in cardiomyocytes derived from human inducible pluripotent stem cells expressing a TNNT2 variant encoding cardiac troponin T (cTnT-I79N
+/−
), which induces hypertrophy, remodelling, abnormalities in excitation–contraction coupling and electrical instabilities (Shafaattalab S
et al.
2021
Front
.
Cell Dev. Biol
.
9
, 787581. (
doi:10.3389/fcell.2021.787581
)). Our search of the literature revealed the novelty of this finding and stimulated us to discuss potential connections between the Notch signalling pathway and familial cardiomyopathies. Our considerations focused on the potential role of these interactions in arrhythmias, microvascular ischaemia, and fibrosis. This finding underscored a need to consider the role of Notch signalling in familial cardiomyopathies which are trigged by sarcomere mutations engaging mechano-signalling pathways for which there is evidence of a role for Notch signalling with crosstalk with Hippo signalling. Our discussion included a role for both cardiac myocytes and non-cardiac myocytes in progression of HCM and DCM.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
Remodelling and dysfunction of the sinus node in pulmonary arterial hypertension
Authors: Logantha Sunil Jit R. J. , Yamanushi Tomoko T. , Absi Mais , Temple Ian P. , Kabuto Hideaki , Hirakawa Eiichiro , Quigley Gillian , Zhang X. , Gurney Alison M. , Hart George , Zhang Henggui , Dobrzynski Halina , Boyett Mark R. , Yanni Joseph
Published: May 2023

Patients with pulmonary arterial hypertension (PAH) have a high burden of arrhythmias, including arrhythmias arising from sinus node dysfunction, and the aim of this study was to investigate the effects of PAH on the sinus node. In the rat, PAH was induced by an injection of monocrotaline. Three weeks after injection, there was a decrease of the intrinsic heart rate (heart rate in the absence of autonomic tone) as well as the normal heart rate, evidence of sinus node dysfunction. In the sinus node of PAH rats, there was a significant downregulation of many ion channels and Ca
2+
-handling genes that could explain the dysfunction: HCN1 and HCN4 (responsible for pacemaker current,
I
f
), Cav1.2, Cav1.3 and Cav3.1 (responsible for L- and T-type Ca
2+
currents,
I
Ca,L
and
I
Ca,T
), NCX1 (responsible for Na
+
–Ca
2+
exchanger) and SERCA2 and RYR2 (Ca
2+
-handling molecules). In the sinus node of PAH rats, there was also a significant upregulation of many fibrosis genes that could also help explain the dysfunction: vimentin, collagen type 1, elastin, fibronectin and transforming growth factor β1. In summary, in PAH, there is a remodelling of ion channel, Ca
2+
-handling and fibrosis genes in the sinus node that is likely to be responsible for the sinus node dysfunction.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
Non-canonical role of the sympathetic nervous system in the day–night rhythm in heart rate
Authors: Anderson Cali , Forte Gabriella , Hu Wei , Zhang Henggui , Boyett Mark R. , D'Souza Alicia
Published: May 2023

Although, for many decades, the day–night rhythm in resting heart rate has been attributed to the parasympathetic branch of the autonomic nervous system (high vagal tone during sleep), recently we have shown that there is a circadian clock in the cardiac pacemaker, the sinus node, and the day–night rhythm in heart rate involves an intrinsic rhythmic transcriptional remodelling of pacemaker ion channels, particularly
Hcn4
. We have now investigated the role of the sympathetic branch of the autonomic nervous system in this and shown it to have a non-canonical role. In mice, sustained long-term block of cardiac β-adrenergic receptors by propranolol administered in the drinking water abolished the day–night rhythm in pacemaking in the isolated sinus node. Concomitant with this, there was a loss of the normal day–night rhythm in many pacemaker ion channel transcripts. However, there was little or no change in the local circadian clock, indicating that the well-known day–night rhythm in sympathetic nerve activity is directly involved in pacemaker ion channel transcription. The day–night rhythm in pacemaking helps explain the occurrence of clinically significant bradyarrhythmias during sleep, and this study improves our understanding of this pathology.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
Targeting p21-activated kinase 1 for development of a novel anti-arrhythmic drug class
Authors: He Yu , Grassam-Rowe Alexander , Lei Ming , Bae James S. H.
Published: May 2023

Evidence accumulated over the past decade suggests that p21-activated kinase 1 (PAK1) is a critical cardiac-protective signalling molecule. The present article provides an updated review of recent findings regarding the role of PAK1 in maintaining normal cardiac electrophysiological function through its regulation of membrane and Ca
2+
clocks. We first overviewed the PAK1 activation mechanism. We then discussed recent updated results showing the action mechanisms of PAK1 signalling on Cav1.2/Cav1.3 (I
CaL
)-mediated Ca
2+
entry, ryanodine receptor type 2-mediated sarcoplasmic reticulum (SR) Ca
2+
release, transcriptional regulation of SR Ca
2+
-ATPase 2a, Na
+
/Ca
2+
exchangers, and Ca
2+
/calmodulin-dependent protein kinase II. Finally, we proposed a new and exciting route for developing a PAK1-based therapeutic strategy for cardiac arrhythmias.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
Functional identification of hot-spot mutations in cardiac calcium channel genes associated with the J wave syndromes
Authors: Zeng Bin , Zhang Xiang , Schimpf Rainer , Powers Andrew , Glikson Michael , Antzelevitch Charles , Hu Dan , Barajas-Martinez Hector
Published: May 2023

J wave syndrome (JWS) is an inherited cardiac channelopathy associated with malignant ventricular arrhythmias and sudden cardiac death (SCD), which comprises early repolarization syndrome and Brugada syndrome. Here, we explore the association between variants in the
L
-type calcium channel gene subunits, α
1C
(
CACNA1C
) and β2b (
CACNB2b
), and the JWS phenotype. Using next-generation genetic sequencing of 402 JWS probands and their family members, we identified a
CACNA1C
-G37R (p.Gly37Arg) mutation in five individuals in four families, two of which had a family history of SCD as well as a
CACNB2b
-S143F (p.Ser143Phe) mutation in seven individuals in three families, two of which had a family history of SCD. The variants were located in exon 2 in
CACNA1C
and exon 5 in
CACNB2b
; both were in highly conserved amino acid residues. Whole-cell patch-clamp results showed that compared with the wild-type group, calcium current density of
CACNB2b-
S143F and
CACNA1C
-G37R were significantly lower displaying a dominant-negative effect. Our findings provide further support for the hypothesis that variants in
CACNA1C
and
CACNB2b
are associated with JWS. The results suggest that mutations in these two genes lead to loss-of-function of the cardiac calcium channel current warranting their inclusion in genetic screening protocols.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
Generation of cardiomyocytes from human-induced pluripotent stem cells resembling atrial cells with ability to respond to adrenoceptor agonists
Authors: Ahmad Faizzan S. , Jin Yongcheng , Grassam-Rowe Alexander , Zhou Yafei , Yuan Meng , Fan Xuehui , Zhou Rui , Mu-u-min Razik , O'Shea Christopher , Ibrahim Ayman M. , Hyder Wajiha , Aguib Yasmine , Yacoub Magdi , Pavlovic Davor , Zhang Yanmin , Tan Xiaoqiu , Lei Ming , Terrar Derek A.
Published: May 2023

Atrial fibrillation (AF) is the most common chronic arrhythmia presenting a heavy disease burden. We report a new approach for generating cardiomyocytes (CMs) resembling atrial cells from human-induced pluripotent stem cells (hiPSCs) using a combination of Gremlin 2 and retinoic acid treatment. More than 40% of myocytes showed rod-shaped morphology, expression of CM proteins (including ryanodine receptor 2,
α
-actinin-2 and F-actin) and striated appearance, all of which were broadly similar to the characteristics of adult atrial myocytes (AMs). Isolated myocytes were electrically quiescent until stimulated to fire action potentials with an AM profile and an amplitude of approximately 100 mV, arising from a resting potential of approximately −70 mV. Single-cell RNA sequence analysis showed a high level of expression of several atrial-specific transcripts including
NPPA
,
MYL7
,
HOXA3
,
SLN
,
KCNJ4
,
KCNJ5
and
KCNA5
. Amplitudes of calcium transients recorded from spontaneously beating cultures were increased by the stimulation of
α
-adrenoceptors (activated by phenylephrine and blocked by prazosin) or
β
-adrenoceptors (activated by isoproterenol and blocked by CGP20712A). Our new approach provides human AMs with mature characteristics from hiPSCs which will facilitate drug discovery by enabling the study of human atrial cell signalling pathways and AF.

This article is part of the theme issue ‘The heartbeat: its molecular basis and physiological mechanisms’.
Learning to Adapt - Deep Reinforcement Learning in Treatment-Resistant Prostate Cancer
Authors: Gallagher Kit , Strobl Maximillian , Gatenby Robert , Maini Philip , Anderson Alexander
Published: May 2023

Standard-of-care treatment regimes have long been designed to for maximal cell kill, yet these strategies often fail when applied to treatment–resistant tumors, resulting in patient relapse. Adaptive treatment strategies have been developed as an alternative approach, harnessing intra-tumoral competition to suppress the growth of treatment resistant populations, to delay or even prevent tumor progression. Following recent clinical implementations of adaptive therapy, it is of significant interest to optimise adaptive treatment protocols. We propose the application of deep reinforcement learning models to provide generalised solutions within adaptive drug scheduling, and demonstrate this framework can outperform the current adaptive protocols, extending time to progression by up to a quarter. This strategy is robust to varying model parameterisations, and the underlying tumor model. We demonstrate the deep learning framework can produce interpretable, adaptive strategies based on a single tumor burden threshold, replicating and informing a novel, analytically–derived optimal treatment strategy with no knowledge of the underlying mathematical tumor model. This approach is highly relevant beyond the simple, analytically–tractable tumor model considered here, demonstrating the capability of deep learning frameworks to help inform and develop treatment strategies in complex settings. Finally, we propose a pathway to integrate mechanistic modelling with DRL to tailor generalist treatment strategies to individual patients in the clinic, generating personalised treatment schedules that consistently outperform clinical standard-of-care protocols.
Food web complexity modulates environmental impacts on food chain length
Authors: Shibasaki Shota , Terui Akira
Published: May 2023

Food chain length (FCL), a crucial aspect of biodiversity, has long been debated for its determinants. Previous studies proposed resource availability, disturbance, and ecosystem size as environmental drivers. However, studies using stable isotope approaches have shown inconsistent results, indicating missing links between environmental drivers and FCL. Here, we hypothesized that species richness and motifs (i.e., 3-species subgraphs) modulated environmental effects on FCL. Combining empirical food webs with ourN-species food web model, we found that FCL disproportionately changed at low species richness with saturation at high species richness. This functional response was essential to the interdependent effects of disturbance and ecosystem size in our model. Disturbance more strongly regulated FCL in smaller ecosystems, where species richness was low. Similarly, increasing ecosystem size enhanced FCL under strong, but not weak, disturbance regimes. Our study suggests that internal food web structure should deepen our understanding of how FCL changes over environments.
Ant impacts on global patterns of bird elevational diversity
Authors: Srinivasan Umesh , Shanker Kartik , Price Trevor D.
Published: May 2023

Across the world’s mountains, elevation-species richness relationships are highly variable. Here, using data on bird species elevational distributions from all 46 of the world’s major mountain ranges, bird species dietary traits, and the distribution of the low-elevation ant genusOecophylla, we show that global patterns in bird elevational diversity are likely to be affected by competition with ants.Oecophyllais an exceptionally abundant and aggressive predator of invertebrates, which preys on the same species that sympatric invertivorous bird species feed on. In mountain ranges withOecophyllapresent in the foothills, maximum species richness of invertivorous birds occurs, on average, at 960m, ∼450m higher than in mountain ranges withoutOecophylla. Further, in mountain ranges withOecophylla, species richness of invertivorous birds increases initially with with elevation to produce a mid-elevation peak in invertivore bird species richness. WhereOecophyllais absent, invertivore bird species richness generally shows monotonic declines with increasing elevation. We attribute the pattern to the following mechanism: first,Oecophyllareduces prey density for invertivorous birds; second, low invertebrate prey abundance reduces invertivorous bird density and third, lower bird density is correlated with lower bird species richness. Because invertivores dominate montane bird communities, global elevational bird diversity patterns are also driven byOecophylla. The findings emphasize how competitive interactions between distantly related taxa set geographical range limits.
scGPT: Towards Building a Foundation Model for Single-Cell Multi-omics Using Generative AI
Authors: Cui Haotian , Wang Chloe , Maan Hassaan , Pang Kuan , Luo Fengning , Wang Bo
Published: May 2023

Generative pre-trained models have achieved remarkable success in various domains such as natural language processing and computer vision. Specifically, the combination of large-scale diverse datasets and pre-trained transformers has emerged as a promising approach for developing foundation models. Drawing parallels between linguistic constructs and cellular biology — where texts comprise words, similarly, cells are defined by genes — our study probes the applicability of foundation models to advance cellular biology and genetics research. Utilizing the burgeoning single-cell sequencing data, we have pioneered the construction of a foundation model for single-cell biology, scGPT, which is based on generative pre-trained transformer across a repository of over 33 million cells. Our findings illustrate that scGPT, a generative pre-trained transformer, effectively distills critical biological insights concerning genes and cells. Through the further adaptation of transfer learning, scGPT can be optimized to achieve superior performance across diverse downstream applications. This includes tasks such as cell-type annotation, multi-batch integration, multi-omic integration, genetic perturbation prediction, and gene network inference. The scGPT codebase is publicly available athttps://github.com/bowang-lab/scGPT.
Collective cell migration due to guidance-by-followers is robust to multiple stimuli
Authors: Müller Robert , Boutillon Arthur , Jahn Diego , Starruß Jörn , David Nicolas B. , Brusch Lutz
Published: May 2023

Collective cell migration is an important process during biological development and tissue repair, but may turn malignant during tumor invasion. Mathematical and computational models are essential to unravel the mechanisms of self-organization that underlie the emergence of collective migration from the interactions among individual cells. Recently, guidance-by-followers was identified as one such underlying mechanism of collective cell migration in the zebrafish embryo. This poses the question how guidance stimuli are integrated when multiple cells interact simultaneously. Here, we extend a recent individual-based model by an integration step of the vectorial guidance stimuli and compare model predictions obtained for various variants of the mechanism (arithmetic mean of stimuli, dominance of stimulus with largest transmission interface, dominance of most head-on stimulus). Simulations are carried out and quantified within the modeling and simulation framework Morpheus. Collective cell migration is sfound to be robust and qualitatively identical for all considered variants of stimulus integration. Moreover, this study highlights the role of individual-based modeling approaches for understanding collective phenomena at the population scale that emerge from cell-cell interactions.