RETRACTED ARTICLE: Two dimensional speckle tracking echocardiography detects cardiac allograft stage III vasculopathy in recipients of heart transplants with preserved systolic function

We, the Editors and Publisher of Acta Cardiologica, have retracted the following article:Michael George Zaki Ghali, Rebecca Stewart, George Zaki Ghali & Wolf Blitzer (2020) Two dimensional speckle tracking echocardiography detects cardiac allograft stage III vasculopathy in recipients of heart transplants with preserved systolic function, Acta Cardiologica, DOI: 10.1080/00015385.2020.1800963Since publication, we have received confirmation from the Karolinska Institutet that the corresponding author is not and has not been affiliated with their institution. The Karolinska Institutet is listed in the above article as having provided funding and ethical approval for the reported study. We have also reached out to the listed co-authors but have not been able to verify their authorship of the article. We have contacted the corresponding author for an explanation, but we have not received a response. As accurately representing authorship, affiliated institution, ethics approval and the source of funding is core to the integrity of published work, we are therefore retracting the article. The corresponding author listed in this publication has been informed.We have been informed in our decision-making by our policy on publishing ethics and integrity and the COPE guidelines on retractions.The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as 'Retracted'.

Retraction: Ghali MGZ, et al. Mechanisms underlying the generation of autonomorespiratory coupling amongst the respiratory central pattern generator, sympathetic oscillators, and cardiovagal premotoneurons. Journal of Integrative Neuroscience. 2020; 19: 521-560

No abstract present.

Mechanisms underlying the generation of autonomorespiratory coupling amongst the respiratory central pattern generator, sympathetic oscillators, and cardiovagal premotoneurons

The respiratory rhythm and pattern and sympathetic and parasympathetic outflows are generated by distinct, though overlapping, propriobulbar arrays of neuronal microcircuit oscillators constituting networks utilizing mutual excitatory and inhibitory neuronal interactions, residing principally within the metencephalon and myelencephalon, and modulated by synaptic influences from the cerebrum, thalamus, hypothalamus, cerebellum, and mesencephalon and ascending influences deriving from peripheral stimuli relayed by cranial nerve afferent axons. Though the respiratory and cardiovascular regulatory effector mechanisms utilize distinct generators, there exists significant overlap and interconnectivity amongst and between these oscillators and pathways, evidenced reciprocally by breathing modulation of sympathetic oscillations and sympathetic modulation of neural breathing. These coupling mechanisms are well-demonstrated coordinately in sympathetic- and respiratory-related central neuronal and efferent neurogram recordings and quantified by the findings of cross-correlation, spectra, and coherence analyses, combined with empirical interventions including lesioning and pharmacological agonist and antagonist microinjection studies, baroloading, barounloading, and hypoxic and/or hypercapnic peripheral and/or central chemoreceptor stimulation. Sympathetic and parasympathetic central neuronal and efferent neural discharge recordings evidence classic fast rhythms produced by propriobulbar neuronal networks located within the medullary division of the lateral tegmental field, coherent with cardiac sympathetic nerve discharge. These neural efferent nerve discharges coordinately evidence slow synchronous oscillations, constituted by Traube Hering (i.e., high frequency), Mayer wave (i.e., medium or low frequency), and vasogenic autorhythmicity (i.e., very low frequency) wave spectral bands. These oscillations contribute to coupling neural breathing, sympathetic oscillations, and parasympathetic cardiovagal premotoneuronal activity. The mechanisms underlying the origins of and coupling amongst, these waves remains to be unresolved.

Structure and function of the perivascular fluid compartment and vertebral venous plexus: Illumining a novel theory on mechanisms underlying the pathogenesis of Alzheimer's, cerebral small vessel, and neurodegenerative diseases

Blood dynamically and richly supplies the cerebral tissue via microvessels invested in pia matter perforating the cerebral substance. Arteries penetrating the cerebral substance derive an investment from one or two successive layers of pia mater, luminally apposed to the pial-glial basal lamina of the microvasculature and abluminally apposed to a series of aquaporin IV-studded astrocytic end feet constituting the soi-disant glia limitans. The full investment of successive layers forms the variably continuous walls of the periarteriolar, pericapillary, and perivenular divisions of the perivascular fluid compartment. The pia matter disappears at the distal periarteriolar division of the perivascular fluid compartment. Plasma from arteriolar blood sequentially transudates into the periarteriolar division of the perivascular fluid compartment and subarachnoid cisterns in precession to trickling into the neural interstitium. Fluid from the neural interstitium successively propagates into the venules through the subarachnoid cisterns and perivenular division of the perivascular fluid compartment. Fluid fluent within the perivascular fluid compartment flows gegen the net direction of arteriovenular flow. Microvessel oscillations at the central tendency of the cerebral vasomotion generate corresponding oscillations of within the surrounding perivascular fluid compartment, interposed betwixt the abluminal surface of the vessels and internal surface of the pia mater. The precise microanatomy of this most fascinating among designable spaces has eluded the efforts of various investigators to interrogate its structure, though most authors non-consensusly concur the investing layers effectively and functionally segregate the perivascular and subarachnoid fluid compartments. Enlargement of the perivascular fluid compartment in a variety of neurological disorders, including senile dementia of the Alzheimer's type and cerebral small vessel disease, may alternately or coordinately constitute a correlative marker of disease severity and a possible cause implicated in the mechanistic pathogenesis of these conditions. Venular pressures modulating oscillatory dynamic flow within the perivascular fluid compartment may similarly contribute to the development of a variety among neurological disorders. An intimate understanding of subtle features typifying microanatomy and microphysiology of the investing structures and spaces of the cerebral microvasculature may powerfully inform mechanistic pathophysiology mediating a variety of neurovascular ischemic, neuroinfectious, neuroautoimmune, and neurodegenerative diseases.

Effects of isoflurane on arterial blood pressure, heart rate, and phrenic nerve discharge in the decerebrate rat

BACKGROUND

The potent inhalational anesthetic isoflurane has widespread use in experimental investigations. Intratracheal administration of the agent attenuates breathing, blood pressure, heart rate, and baroreflex control of heart rate. Concurrent effects of potent inhalational anesthetics on hemodynamic waves and neural respiratory output have yet to be systematically interrogated.

OBJECTIVES

We sought to determine the effects of administering isoflurane to unanesthetized decerebrate animals upon breathing, dynamic arterial pressure magnitude, and ventricular depolarization frequency.

METHODS AND RESULTS

Experiments were conducted on ten unanesthetized decerebrate Sprague-Dawley adult male rats. Saturation of a hyperoxic gas mixture with 2.0% isoflurane in supracollicularly decerebrate rats having undergone successful weaning from isoflurane anesthesia quantally reduced phrenic nerve bursting frequency and coupling with the ventilator cycle from 1:1 to 1:2 and prolonged phrenic expiratory duration, though failed to modify phrenic inspiratory burst amplitude or duration. Isoflurane also reduced dynamic arterial pressure magnitude and heart rate, increased heart rate variability, and reduced blood pressure variability.

CONCLUSIONS

Use of unanesthetized decerebrate preparations eschewing the confounding effects of anesthesia upon neural networks may prudently supplant the use of anesthetized animals when seeking to mechanistically interrogate propriobulbar interneuronal microcircuit oscillators constituting the respiratory rhythm and pattern generator, sympathetic oscillators, and cardiovagal premotoneurons.

β adrenergic receptor modulated signaling in glioma models: promoting β adrenergic receptor-β arrestin scaffold-mediated activation of extracellular-regulated kinase 1/2 may prove to be a panacea in the treatment of intracranial and spinal malignancy and extra-neuraxial carcinoma

Neoplastically transformed astrocytes express functionally active cell surface β adrenergic receptors (βARs). Treatment of glioma models in vitro and in vivo with β adrenergic agonists variably amplifies or attenuates cellular proliferation. In the majority of in vivo models, β adrenergic agonists generally reduce cellular proliferation. However, treatment with β adrenergic agonists consistently reduces tumor cell invasive potential, angiogenesis, and metastasis. β adrenergic agonists induced decreases of invasive potential are chiefly mediated through reductions in the expression of matrix metalloproteinases types 2 and 9. Treatment with β adrenergic agonists also clearly reduce tumoral neoangiogenesis, which may represent a putatively useful mechanism to adjuvantly amplify the effects of bevacizumab. Bevacizumab is a monoclonal antibody targeting the vascular endothelial growth factor receptor. We may accordingly designate βagonists to represent an enhancer of bevacizumab. The antiangiogenic effects of β adrenergic agonists may thus effectively render an otherwise borderline effective therapy to generate significant enhancement in clinical outcomes. β adrenergic agonists upregulate expression of the major histocompatibility class II DR alpha gene, effectively potentiating the immunogenicity of tumor cells to tumor surveillance mechanisms. Authors have also demonstrated crossmodal modulation of signaling events downstream from the β adrenergic cell surface receptor and microtubular polymerization and depolymerization. Complex effects and desensitization mechanisms of the β adrenergic signaling may putatively represent promising therapeutic targets. Constant stimulation of the β adrenergic receptor induces its phosphorylation by β adrenergic receptor kinase (βARK), rendering it a suitable substrate for alternate binding by β arrestins 1 or 2. The binding of a β arrestin to βARK phosphorylated βAR promotes receptor mediated internalization and downregulation of cell surface receptor and contemporaneously generates a cell surface scaffold at the βAR. The scaffold mediated activation of extracellular regulated kinase 1/2, compared with protein kinase A mediated activation, preferentially favors cytosolic retention of ERK1/2 and blunting of nuclear translocation and ensuant pro-transcriptional activity. Thus, βAR desensitization and consequent scaffold assembly effectively retains the cytosolic homeostatic functions of ERK1/2 while inhibiting its pro-proliferative effects. We suggest these mechanisms specifically will prove quite promising in developing primary and adjuvant therapies mitigating glioma growth, angiogenesis, invasive potential, and angiogenesis. We suggest generating compounds and targeted mutations of the β adrenergic receptor favoring β arrestin binding and scaffold facilitated activation of ERK1/2 may hold potential promise and therapeutic benefit in adjuvantly treating most or all cancers. We hope our discussion will generate fruitful research endeavors seeking to exploit these mechanisms.

Microneurosurgical techniques and perioperative strategies utilized to optimize experimental supracollicular decerebration in rats

Decerebration permits neurophysiological experimentation absent the confounding effects of anesthesia. Use of the unanesthetized decerebrate preparation in vivo offers several advantages compared with recordings performed in reduced slice preparations, providing the capacity to perform extracellular and intracellular neuronal recordings in the presence of an intact brainstem network. The decerebration procedure typically generates variable degrees of blood loss, which often compromises the hemodynamic stability of the preparation. We describe our microsurgical techniques and discuss microsurgical pearls utilized in order to consistently generate normotensive supracollicularly decerebrate preparations of the rat, exhibiting an augmenting pattern of phrenic nerve discharge. In brief, we perform bilateral ligation of the internal carotid arteries, biparietal craniectomies, securing of the superior sagittal sinus to the overlying strip of bone, removal of the median strip of bone overlying the superior sagittal sinus, supracollicular decerebrative encephalotomy, removal of the cerebral hemispheres, and packing of the anterior and middle cranial fossae with thrombin soaked gelfoam sponges. Hypothermia and potent inhalational anesthesia ensure neuroprotection during postdecerebrative neurogenic shock. Advantages of our approach include a bloodless and fast operation with a nil percent rate of operative mortality. We allow animal arterial pressure to recover gradually in parallel with gentle weaning of anesthesia following decerebration, performed contemporaneously with the provision of the neuromuscular antagonist vecuronium. Anesthetic weaning and institution of vecuronium should be contemporaneous, coordinate, gentle, gradual, and guided by the spontaneous recovery of the arterial blood pressure. We describe our microsurgical techniques and perioperative management strategy designed to achieve decerebration and accordingly survey the literature on techniques used across several studies in achieving these goals.

Clinical utility and versatility of the petrous segment of the internal carotid artery in revascularization

Direct approaches to high cervical lesions, including tumors and aneurysms, carry significant risks. This renders alternative approaches desirable, with vascular disease amenable to exclusion and revascularization to the intracranial circulation, including the petrous or supraclinoid segments of the internal carotid artery (ICA). The cervicopetrous ICA bypass via saphenous venous grafting has proven an effective strategy for treating and excluding these lesions. In current practice, this is performed via an extradural subtemporal approach to access the petrous segment of the ICA and a cervical incision for access to the cervical ICA. The venous graft is alternately tunneled subcutaneously or in situ through the cervical ICA, with the latter eschewing external compression, kinking, and torsion, which increases risk of graft thrombosis with the former. Maxillary or middle meningeal arteries may also serve as donors to the petrous ICA. Moreover, the petrous ICA may be used as a donor in revascularization procedures, to the supraclinoid segment of the ICA and the middle cerebral artery, with petrous supraclinoid and petrous-MCA bypasses described. Clinical utility and operative approaches bypassing to or from the petrous ICA in revascularization procedures are reviewed and discussed.

Nafamostat mesylate attenuates the pathophysiologic sequelae of neurovascular ischemia

Nafamostat mesylate, an apparent soi-disant panacea of sorts, is widely used to anticoagulate patients undergoing hemodialysis or cardiopulmonary bypass, mitigate the inflammatory response in patients diagnosed with acute pancreatitis, and reverse the coagulopathy of patients experiencing the commonly preterminal disseminated intravascular coagulation in the Far East. The serine protease inhibitor nafamostat mesylate exhibits significant neuroprotective effects in the setting of neurovascular ischemia. Nafamostat mesylate generates neuroprotective effects by attenuating the enzymatic activity of serine proteases, neuroinflammatory signaling cascades, and the endoplasmic reticulum stress responses, downregulating excitotoxic transient receptor membrane channel subfamily 7 cationic currents, modulating the activity of intracellular signal transduction pathways, and supporting neuronal survival (brain-derived neurotrophic factor/TrkB/ERK1/2/CREB, nuclear factor kappa B. The effects collectively reduce neuronal necrosis and apoptosis and prevent ischemia mediated disruption of blood-brain barrier microarchitecture. Investigational clinical applications of these compounds may mitigate ischemic reperfusion injury in patients undergoing cardiac, hepatic, renal, or intestinal transplant, preventing allograft rejection, and treating solid organ malignancies. Neuroprotective effects mediated by nafamostat mesylate support the wise conduct of randomized prospective controlled trials in Western countries to evaluate the clinical utility of this compound.

Spinal genesis of Mayer waves

Variability in cardiovascular spectra was first described by Stephan Hales in 1733. Traube and Hering initially noted respirophasic variation of the arterial pressure waveform in 1865 and Sigmund Mayer noted a lower frequency oscillation of the same in anesthetized rabbits in 1876. Very low frequency oscillations were noted by Barcroft and Nisimaru in 1932, likely representing vasogenic autorhythmicity. While the origins of Traube Hering and very low frequency oscillatory variability in cardiovascular spectra are well described, genesis mechanisms and functional significance of Mayer waves remain in controversy. Various theories have posited baroreflex and central supraspinal mechanisms for genesis of Mayer waves. Several studies have demonstrated the persistence of Mayer waves following high cervical transection, indicating a spinal capacity for genesis of these oscillations. We suggest a general tendency for central sympathetic neurons to oscillate at the Mayer wave frequency, the presence of multiple Mayer wave oscillators throughout the brainstem and spinal cord, and possible contemporaneous genesis by baroreflex and vasomotor mechanisms.

WITHDRAWN: Hybrid surgical endovascular theatres in the treatment of arteriovenous malformations

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

WITHDRAWN: Multimodal treatment and microsurgical resection of basal ganglionic and thalamic arteriovenous malformations

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Transvenous embolization of arteriovenous malformations

Embolization of arteriovenous malformations is characteristically used as part of a multimodal treatment approach, pre-operatively to facilitate microsurgical resection or as a preradiosurgical adjunct. The concept of AVM cure via embolization alone has gained popularity in recent years. Embolization of AVMs has been most commonly performed transarterially, with the transvenous route traditionally eschewed given concern over precipitating premature venous occlusion and consequent hemorrhage. However, the transvenous approach in treating AVMs offers several distinct advantages compared to the transarterial route and can be used in instances when the latter is not feasible, with several series having proven its efficacy and safety. Conceptually, AVM embolization performed via the transvenous route achieves complete obliteration by directly and facilely targeting the nidus. Nidal embolisate penetration is facilitated by control of arterial inflow via systemic or local hypotension. Innovation in endovascular strategies has led to significantly improved obliteration rates. The experience with transvenous AVM embolization is reviewed and discussed.

Intracranial Venous Hypertension in Craniosynostosis: Mechanistic Underpinnings and Therapeutic Implications

Patients with complex, multisutural, and syndromic craniosynostosis (CSO) frequently exhibit intracranial hypertension. The intracranial hypertension cannot be entirely attributed to the craniocephalic disproportion with calvarial restriction because cranial vault expansion has not consistently alleviated elevated intracranial pressure. Evidence has most strongly supported a multifactorial interaction, including venous hypertension along with other pathogenic processes. Patients with CSO exhibit marked venous anomalies, including stenosis of the jugular-sigmoid complex, transverse sinuses, and extensive transosseous venous collaterals. These abnormal intracranial-extracranial occipital venous collaterals might represent anomalous development, with persistence and subsequent enlargement of channels normally present in the fetus, either as a primary defect or as nonregression in response to failure of the development of the jugular-sigmoid complexes. It has been suggested by some investigators that venous hypertension in patients with CSO could be treated directly via jugular foraminoplasty, venous stenting, or jugular venous bypass, although these options are not in common clinical practice. Obstructive sleep apnea, occurring as a consequence of midface hypoplasia, can also contribute to intracranial hypertension in patients with syndromic CSO. Thus, correction of facial deformities, as well as posterior fossa decompression, could also play important roles in the treatment of intracranial hypertension. Determining the precise mechanistic underpinnings underlying intracranial hypertension in any given patient with CSO requires individualized evaluation and management.