Brain charts for the human lifespan

Over the past few decades, neuroimaging has become a ubiquitous tool in basic research and clinical studies of the human brain. However, no reference standards currently exist to quantify individual differences in neuroimaging metrics over time, in contrast to growth charts for anthropometric traits such as height and weight1. Here we assemble an interactive open resource to benchmark brain morphology derived from any current or future sample of MRI data ( http://www.brainchart.io/ ). With the goal of basing these reference charts on the largest and most inclusive dataset available, acknowledging limitations due to known biases of MRI studies relative to the diversity of the global population, we aggregated 123,984 MRI scans, across more than 100 primary studies, from 101,457 human participants between 115 days post-conception to 100 years of age. MRI metrics were quantified by centile scores, relative to non-linear trajectories2 of brain structural changes, and rates of change, over the lifespan. Brain charts identified previously unreported neurodevelopmental milestones3, showed high stability of individuals across longitudinal assessments, and demonstrated robustness to technical and methodological differences between primary studies. Centile scores showed increased heritability compared with non-centiled MRI phenotypes, and provided a standardized measure of atypical brain structure that revealed patterns of neuroanatomical variation across neurological and psychiatric disorders. In summary, brain charts are an essential step towards robust quantification of individual variation benchmarked to normative trajectories in multiple, commonly used neuroimaging phenotypes.

A radio counterpart to a neutron star merger

Gravitational waves have been detected from a binary neutron star merger event, GW170817. The detection of electromagnetic radiation from the same source has shown that the merger occurred in the outskirts of the galaxy NGC 4993, at a distance of 40 megaparsecs from Earth. We report the detection of a counterpart radio source that appears 16 days after the event, allowing us to diagnose the energetics and environment of the merger. The observed radio emission can be explained by either a collimated ultrarelativistic jet, viewed off-axis, or a cocoon of mildly relativistic ejecta. Within 100 days of the merger, the radio light curves will enable observers to distinguish between these models, and the angular velocity and geometry of the debris will be directly measurable by very long baseline interferometry.

The local repressor AcrR plays a modulating role in the regulation of acrAB genes of Escherichia coli by global stress signals

Genes acrAB encode a multidrug efflux pump in Escherichia coli. We have previously reported that transcription of acrAB is increased under general stress conditions (i.e. 4% ethanol, 0.5 M NaCl, and the stationary phase in Luria-Bertani medium). In this study, lacZ transcriptional fusions and an in vitro gel mobility shift assay have been utilized to study the mechanisms governing the regulation of acrAB. We found that a closely linked gene, acrR, encoded a repressor of acrAB. Nevertheless, the general stress conditions increased transcription of acrAB in the absence of functional AcrR, and such conditions surprisingly increased the transcription of acrR even more strongly than that of acrAB. These results suggest that the general-stress-induced transcription of acrAB is primarily mediated by global regulatory pathway(s), and that one major role of AcrR is to function as a specific secondary modulator to fine tune the level of acrAB transcription and to prevent the unwanted overexpression of acrAB. To our knowledge, this represents a novel mechanism of regulating gene expression in E. coli. Evidence also suggests that the up-regulation of acrAB expression under general stress conditions is not likely to be mediated by the known global regulators, such as MarA or SoxS, although elevated levels of these proteins were shown to increase the transcription of acrAB.

Cellular electrophysiological effects of hyperthermia on isolated guinea pig papillary muscle. Implications for catheter ablation

BACKGROUND

The primary mechanism of tissue injury by radiofrequency catheter ablation is presumed to be thermally mediated. However, the myocardial cellular electrophysiological effects of hyperthermia are not well characterized. We used an in vitro model of isolated guinea pig right ventricular papillary muscle to investigate the acute cellular electrophysiological effects of hyperthermia.

METHODS AND RESULTS

Excised guinea pig right ventricular papillary muscles were pinned in a high-flow tissue bath and superfused with Tyrode's solution at 37.0 +/- 0.5 degrees C. The superfusate temperature was rapidly changed to 38.0 to 56.0 degrees C for 60 seconds and then returned to 37.0 degrees C. Conventional microelectrodes were used to measure membrane potential (Vm), maximum rate of rise of the action potential (dV/dtmax), and action potential (AP) amplitude and AP duration at 50% (APD50) and 90% (APD90) repolarization. Hyperthermia resulted in (1) a progressive depolarization of Vm at temperatures > or = 40.0 degrees C, which became more prominent at temperatures > or = 45.0 degrees C; (2) changes in the AP characterized by a temperature-dependent increase in dV/dtmax and a temperature-dependent decrease in AP amplitude, APD50, and APD90; (3) reversible loss of cellular excitability within a temperature range of 42.7 to 51.3 degrees C (median, 48.0 degrees C); (4) irreversible loss of cellular excitability and tissue injury at temperatures > or = 50.0 degrees C; and (5) the development of abnormal automaticity at temperatures > 45.0 degrees C.

CONCLUSIONS

Hyperthermia causes significant changes in myocardial cellular electrophysiological properties that include membrane depolarization, reversible and irreversible loss of excitability, and abnormal automaticity. There appear to be specific temperature ranges for reversible and irreversible electrophysiological changes. These observations may have important implications for tissue temperature monitoring during radiofrequency catheter ablation.

Clinical characteristics with inflammation profiling of long COVID and association with 1-year recovery following hospitalisation in the UK: a prospective observational study

BACKGROUND

No effective pharmacological or non-pharmacological interventions exist for patients with long COVID. We aimed to describe recovery 1 year after hospital discharge for COVID-19, identify factors associated with patient-perceived recovery, and identify potential therapeutic targets by describing the underlying inflammatory profiles of the previously described recovery clusters at 5 months after hospital discharge.

METHODS

The Post-hospitalisation COVID-19 study (PHOSP-COVID) is a prospective, longitudinal cohort study recruiting adults (aged ≥18 years) discharged from hospital with COVID-19 across the UK. Recovery was assessed using patient-reported outcome measures, physical performance, and organ function at 5 months and 1 year after hospital discharge, and stratified by both patient-perceived recovery and recovery cluster. Hierarchical logistic regression modelling was performed for patient-perceived recovery at 1 year. Cluster analysis was done using the clustering large applications k-medoids approach using clinical outcomes at 5 months. Inflammatory protein profiling was analysed from plasma at the 5-month visit. This study is registered on the ISRCTN Registry, ISRCTN10980107, and recruitment is ongoing.

FINDINGS

2320 participants discharged from hospital between March 7, 2020, and April 18, 2021, were assessed at 5 months after discharge and 807 (32·7%) participants completed both the 5-month and 1-year visits. 279 (35·6%) of these 807 patients were women and 505 (64·4%) were men, with a mean age of 58·7 (SD 12·5) years, and 224 (27·8%) had received invasive mechanical ventilation (WHO class 7-9). The proportion of patients reporting full recovery was unchanged between 5 months (501 [25·5%] of 1965) and 1 year (232 [28·9%] of 804). Factors associated with being less likely to report full recovery at 1 year were female sex (odds ratio 0·68 [95% CI 0·46-0·99]), obesity (0·50 [0·34-0·74]) and invasive mechanical ventilation (0·42 [0·23-0·76]). Cluster analysis (n=1636) corroborated the previously reported four clusters: very severe, severe, moderate with cognitive impairment, and mild, relating to the severity of physical health, mental health, and cognitive impairment at 5 months. We found increased inflammatory mediators of tissue damage and repair in both the very severe and the moderate with cognitive impairment clusters compared with the mild cluster, including IL-6 concentration, which was increased in both comparisons (n=626 participants). We found a substantial deficit in median EQ-5D-5L utility index from before COVID-19 (retrospective assessment; 0·88 [IQR 0·74-1·00]), at 5 months (0·74 [0·64-0·88]) to 1 year (0·75 [0·62-0·88]), with minimal improvements across all outcome measures at 1 year after discharge in the whole cohort and within each of the four clusters.

INTERPRETATION

The sequelae of a hospital admission with COVID-19 were substantial 1 year after discharge across a range of health domains, with the minority in our cohort feeling fully recovered. Patient-perceived health-related quality of life was reduced at 1 year compared with before hospital admission. Systematic inflammation and obesity are potential treatable traits that warrant further investigation in clinical trials.

FUNDING

UK Research and Innovation and National Institute for Health Research.

Calcitonin gene-related peptide: potent vasodilator and major product of calcitonin gene

In addition to calcitonin and katacalcin, the human calcitonin gene encodes a novel peptide--calcitonin gene-related peptide (CGRP)--a potent vasodilator. A sensitive and specific radioimmunoassay was developed to study plasma levels of CGRP in normal subjects. CGRP circulates at five times the concentration of calcitonin, suggesting that it may be an important physiological regulator of vascular tone and blood flow.

A protocol for the videofluorographic swallowing study

This paper presents a detailed protocol for performing the videofluorographic swallowing study (VFSS), and describes how it evolved from its antecedents. The objectives of the VFSS are both diagnostic and therapeutic. Preparing for the VFSS is described, including the equipment, food preparation, and a brief discussion of the clinical evaluation. The detailed description of the VFSS procedure covers the position of the patient, the foods presented, the views obtained, modifications of feeding and swallowing that are commonly employed, the standardized set of observations, and reporting the results. Criteria for deviating from the protocol or aborting the study are presented. The VFSS does not necessarily end when a patient aspirates. Indeed, the complete evaluation of aspiration, and the effects of maneuvers designed to reduce it, is a major purpose of the VFSS. Modifications of feeding and swallowing are tested empirically during the study. The modifications include therapeutic and compensatory techniques that may improve the safety and efficiency of swallowing. A rationale for deciding which modifications to test in a given patient is discussed. The protocol has been used successfully in more than 350 patients. It has improved the efficiency and quality of our videofluorographic examinations.

Risk of lymphoma subtypes after solid organ transplantation in the United States

BACKGROUND

Solid organ transplant recipients have high risk of lymphomas, including non-Hodgkin lymphoma (NHL) and Hodgkin lymphoma (HL). A gap in our understanding of post-transplant lymphomas involves the spectrum and associated risks of their many histologic subtypes.

METHODS

We linked nationwide data on solid organ transplants from the US Scientific Registry of Transplant Recipients (1987-2008) to 14 state and regional cancer registries, yielding 791 281 person-years of follow-up for 19 distinct NHL subtypes and HL. We calculated standardised incidence ratios (SIRs) and used Poisson regression to compare SIRs by recipient age, transplanted organ, and time since transplantation.

RESULTS

The risk varied widely across subtypes, with strong elevations (SIRs 10-100) for hepatosplenic T-cell lymphoma, Burkitt's lymphoma, NK/T-cell lymphoma, diffuse large B-cell lymphoma, and anaplastic large-cell lymphoma (both systemic and primary cutaneous forms). Moderate elevations (SIRs 2-4) were observed for HL and lymphoplasmacytic, peripheral T-cell, and marginal zone lymphomas, but SIRs for indolent lymphoma subtypes were not elevated. Generally, SIRs were highest for younger recipients (<20 years) and those receiving organs other than kidneys.

CONCLUSION

Transplant recipients experience markedly elevated risk of a distinct spectrum of lymphoma subtypes. These findings support the aetiologic relevance of immunosuppression for certain subtypes and underscore the importance of detailed haematopathologic workup for transplant recipients with suspected lymphoma.

Double dose-intensive chemotherapy with autologous marrow and peripheral-blood progenitor-cell support for metastatic breast cancer: a feasibility study

PURPOSE

Twenty-seven percent of responding metastatic breast cancer patients remain progression-free a median 29 months following one intensification course of cyclophosphamide (6,000 mg/m2), thiotepa (500 mg/m2), and carboplatin (800 mg/m2) (CTCb) with autologous bone marrow transplantation (ABMT). European investigators report high complete response (CR) rates with melphalan for breast cancer. This trial studied the feasibility of two tandem high-dose intensification therapies in an attempt to optimize disease response and duration.

PATIENTS AND METHODS

Women with at least partial responses (PRs) to induction therapy received melphalan (140 to 180 mg/m2), followed 24 hours later by chemotherapy and granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral-blood progenitor cells (PBPCs) and subsequent G-CSF until WBC recovery. The women were monitored as outpatients. After recovery, patients were hospitalized for CTCb with marrow, PBPC, and G-CSF support.

RESULTS

Twenty women were assessable. Fourteen (70%) required admission for fever (10% infection) or mucositis (35%) after melphalan (median stay, 5 days). Median days of absolute neutrophil count (ANC) less than 500/microL and platelet count less than 20,000/microL were 6 and 5.5, respectively. Patients received CTCb 25 days after starting melphalan and had a hospital stay of 25 days. After CTCb, median days of ANC less than 500/microL and platelet count less than 20,000/microL were 11.5 and 24, respectively. Grade 3 toxicities included venoocclusive disease (VOD) (10%), mucositis (45%), and infection (20%). Toxicities were reversible without mortality.

CONCLUSION

With mobilized PBPCs and growth factors, double dose-intensive chemotherapy is feasible with acceptable toxicity. When compared with trials using marrow alone, these supportive adjuncts decrease sepsis and organ toxicity. The concepts of dose and dose-intensity may now be more effectively and safely studied in chemosensitive tumors, including breast cancer.

Long-term outcome of surgery for dogs with cranial cruciate ligament deficiency

Fifty-eight dogs with cranial cruciate ligament deficiency were assessed and treated surgically. At an average of 50 months postoperatively, the functional outcome was assessed by means of an owner-based clinical assessment and a clinical examination. Client-based data were available for 26 dogs and 20 dogs were reassessed after 50 months. The results were compared with the initial values and with data from an assessment 13 months postoperatively. The level of disability at 50 months was judged to be significantly less than initially. However, there were no differences between the initial assessments and those made after 50 months for the perceived 'effect of cold weather' and the dogs' 'ability to jump', despite both measures having improved after 13 months. Age and meniscal injury were identified as poor prognostic indicators for the long-term outcome. The equivalent joint on the contralateral limb deteriorated significantly during the study.

Chronic Repetitive Mild Traumatic Brain Injury Results in Reduced Cerebral Blood Flow, Axonal Injury, Gliosis, and Increased T-Tau and Tau Oligomers

Exposure to repetitive mild traumatic brain injury (mTBI) is a risk factor for chronic traumatic encephalopathy, which is characterized by patchy deposition of hyperphosphorylated tau aggregates in neurons and astrocytes at the depths of cortical sulci. We developed an mTBI paradigm to explore effects of repetitive concussive-type injury over several months in mice with a human tau genetic background (hTau). Two injuries were induced in the hTau mice weekly over a period of 3 or 4 months and the effects were compared with those in noninjured sham animals. Behavioral and in vivo measures and detailed neuropathological assessments were conducted 6 months after the first injury. Our data confirm impairment in cerebral blood flow and white matter damage. This was accompanied by a 2-fold increase in total tau levels and mild increases in tau oligomers/conformers and pTau (Thr231) species in brain gray matter. There was no evidence of neurofibrillary/astroglial tangles, neuropil threads, or perivascular foci of tau immunoreactivity. There were neurobehavioral deficits (ie, disinhibition and impaired cognitive performance) in the mTBI animals. These data support the relevance of this new mTBI injury model for studying the consequences of chronic repetitive mTBI in humans, and the role of tau in TBI.

Multiple ionic mechanisms mediate inhibition of rat motoneurones by inhalation anaesthetics

1. We studied the effects of inhalation anaesthetics on the membrane properties of hypoglossal motoneurones in a neonatal rat brainstem slice preparation. 2. In current clamp, halothane caused a membrane hyperpolarization that was invariably associated with decreased input resistance; in voltage clamp, halothane induced an outward current and increased input conductance. Qualitatively similar results were obtained with isoflurane and sevoflurane. 3. The halothane current reversed near the predicted K+ equilibrium potential (EK) and was reduced in elevated extracellular K+ and in the presence of Ba2+ (2 mM). Moreover, the Ba2+-sensitive component of halothane current was linear and reversed near EK. The halothane current was not sensitive to glibenclamide or thyrotropin-releasing hormone (TRH). Therefore, the halothane current was mediated, in part, by activation of a Ba2+-sensitive K+ current distinct from the ATP- and neurotransmitter-sensitive K+ currents in hypoglossal motoneurones. 4. Halothane also inhibited Ih, a hyperpolarization-activated cationic current; this was primarily due to a decrease in the absolute amount of current, although halothane also caused a small, but statistically significant, shift in the voltage dependence of Ih activation. Extracellular Cs+ (3 mM) blocked Ih and a component of halothane-sensitive current with properties reminiscent of Ih. 5. A small component of halothane current, resistant to Ba2+ and Cs+, was observed in TTX-containing solutions at potentials depolarized to approximately -70 mV. Partial Na+ substitution by N-methyl-D-glucamine completely abolished this residual current, indicating that halothane also inhibited a TTX-resistant Na+ current active near rest potentials. 6. Thus, halothane activates a Ba2+-sensitive, relatively voltage-independent K+ current and inhibits both Ih and a TTX-insensitive persistent Na+ current in hypoglossal motoneurones. These effects of halothane decrease motoneuronal excitability and may contribute to the immobilization that accompanies inhalation anaesthesia.

Poisoning with 4-aminopyridine: report of three cases

Four-aminopyridine is an acutely toxic avicide considered by the manufacturer to be a bird "repellant" because only a small number of birds are acutely poisoned, become disoriented, and emit a distress cry frightening other members of the flock. Four-aminopyridine dramatically enhances transmission at the neuromuscular junction and other synapses, and has been employed clinically in the treatment of prolonged paralysis caused by antibiotics and muscle relaxants, and in the Eaton-Lambert syndrome. In this paper we report the results of an acute poisoning misadventure in three adult males. We review the animal toxicology, summarize the neurophysiological research using 4-AP as a potassium channel blocker, comment on clinical applications, and outline the management of overdose with this agent.

Effects of internal divalent cations on voltage-clamped squid axons

We have studied the effects of internally applied divalent cations on the ionic currents of voltage-clamped squid giant axons. Internal concentrations of calcium up to 10 mM have little, if any, effect on the time-course, voltage dependence, or magnitude of the ionic currents. This is inconsistent with the notion that an increase in the internal calcium concentration produced by an inward calcium movement with the action potential triggers sodium inactivation or potassium activation. Low internal zinc concentrations ( approximately 1 mM) selectively and reversibly slow the kinetics of the potassium current and reduce peak sodium current by about 40% with little effect on the voltage dependence of the ionic currents. Higher concentrations ( approximately 10 mM) produce a considerable (ca. 90%) nonspecific reversible reduction of the ionic currents. Large hyperpolarizing conditioning pulses reduce the zinc effect. Internal zinc also reversibly depolarizes the axon by 20-30 mV. The effects of internal cobalt, cadmium, and nickel are qualitatively similar to those of zinc: only calcium among the cations tested is without effect.

Isoflurane, but not halothane, induces protection of human myocardium via adenosine A1 receptors and adenosine triphosphate-sensitive potassium channels

BACKGROUND

Volatile anesthetics produce differing degrees of myocardial protection in animal models of ischemia. The purpose of the current investigation was to determine the influence of isoflurane and halothane on myocardial protection in a human model of simulated ischemia and the role of adenosine A1 receptors and adenosine triphosphate-sensitive potassium (KATP) channels in the anesthetic pathway.

METHODS

Human atrial trabecular muscles were superfused with oxygenated Krebs-Henseleit buffer and stimulated at 1 Hz, with recording of maximum contractile force. Fifteen minutes before a 30-min anoxic insult, muscles were pretreated for 5 min with either anoxia, the A1 agonist N6-cyclohexyladenosine, 1% halothane or 1.2% isoflurane. These treatments were also performed in the presence of either the KATP channel antagonist glibenclamide or the A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). Anesthetic effects were also determined on KATP currents in isolated whole cell voltage-clamped human atrial myocytes.

RESULTS

Recovery of force (recorded 60 min after anoxia) in isoflurane-pretreated muscles was reduced from 76.6 +/- 7.5% of baseline to 43.7 +/- 7.1% by pretreatment with glibenclamide, and to 52.5 +/- 6.2% by pretreatment with DPCPX. Halothane treatment provided no cardioprotection and seemed to inhibit protection by anoxic preconditioning. Halothane decreased whole cell KATP currents in atrial myocytes, whereas isoflurane had no effects.

CONCLUSIONS

This study demonstrates the cardioprotective effects of isoflurane in contrast to the effects of halothane. Furthermore, A1 receptors and KATP channels seem to mediate the beneficial effects of anoxia and isoflurane in human myocardium.

Myocardial depressant effects of sevoflurane. Mechanical and electrophysiologic actions in vitro

BACKGROUND

The effects of anesthetic concentrations of sevoflurane were studied in isolated myocardial tissue to delineate the mechanisms by which cardiac function is altered.

METHODS

Isometric force of isolated guinea pig ventricular papillary muscle was studied at 37 degrees C in normal and 26 mM K+ Tyrode's solution at various stimulation rates. Normal and slow action potentials were evaluated using conventional microelectrodes. Effects of sevoflurane on sarcoplasmic reticulum function in situ were also evaluated by its effect on rapid cooling contractures, which are known to activate Ca2+ release from the sarcoplasmic reticulum, and on concentrations of rat papillary muscle. Finally, Ca2+ and K+ currents of isolated guinea pig ventricular myocytes were examined using the whole-cell patch clamp technique.

RESULTS

Sevoflurane equivalent to 1.4% and 2.8% depressed guinea pig myocardial contractions to approximately 85 and approximately 65% of control, respectively, although the maximum rate of force development at 2 or 3 Hz and force in rat myocardium after rest showed less depression. In the partially depolarized, beta-adrenergically stimulated myocardium, sevoflurane selectively depressed late peak force without changing early peak force, whereas it virtually abolished rapid cooling contractures. Sevoflurane did not alter the peak amplitude or maximum depolarization rate of normal and slow action potentials, but action potential duration was significantly prolonged. In isolated guinea pig myocytes at room temperature, 0.7 mM sevoflurane (equivalent to 3.4%) depressed peak Ca2+ current by approximately 25% and increased the apparent rate of inactivation. The delayed outward K+ current was markedly depressed, but the inwardly rectifying K+ current was only slightly affected by 0.35 mM sevoflurane.

CONCLUSIONS

These results suggest that the direct myocardial depressant effects of sevoflurane are similar to those previously described for isoflurane. The rapid initial release of Ca2+ from the sarcoplasmic reticulum is not markedly decreased, although certain release pathway, specifically those induced by rapid cooling, appear to be depressed. Contractile depression may be partly related to the depression of Ca2+ influx through the cardiac membrane. The major electrophysiologic effect of sevoflurane seems to be a depression of the delayed outward K+ current, which appears to underlie the increased action potential duration.

Associations between bladder cancer risk factors and tumor stage and grade at diagnosis

Using data on 1,860 bladder cancer cases and 3,934 population-based controls from the National Bladder Cancer Study, we examined associations between suspected bladder cancer risk factors and tumor stage and grade. Employment in a high-risk occupation was associated with the entire clinical spectrum of bladder cancer rather than a particular tumor stage or grade. For example, relative risks (RR) were similar for noninvasive and invasive disease (1.5 and 1.6, respectively). Cigarette smoking also increased risk of the entire clinical spectrum of bladder cancer, but the more advanced the stage, the stronger the effect. For example, relative risks of noninvasive and invasive bladder cancer for current heavy smokers were 3.0 and 5.2, respectively. Cigarette smoking was associated with higher risk of low-grade than high-grade tumors, once stage of disease was taken into account. Compared with whites, nonwhites were at a lower risk of noninvasive bladder cancer (RR = 0.4) but at similar risk of invasive bladder cancer (RR = 1.1), a pattern indicating racial differences in health practices related to bladder cancer detection. History of urinary tract infections and bladder stones was associated with increasing relative risks for advanced tumor stage. Heavy artificial sweetener use was associated with higher-grade, poorly differentiated tumors. Coffee consumption and family history of bladder cancer were not consistently associated with tumor stage or grade. Overall, different clinical presentations of bladder cancer share most suspected bladder cancer risk factors, including employment in a high-risk occupation and cigarette smoking.

Differential depression of myocardial contractility by halothane and isoflurane in vitro

Depressant effects of halothane and isoflurane on isolated right ventricular guinea pig papillary muscle bathed in Tyrode's solution at 37 degrees C were examined. Contractions were elicited by stimulation through external field electrodes while tension was recorded continuously and the intracellular cardiac action potential (AP) was monitored simultaneously by microelectrodes. The time differential of tension (dT/dt) and of membrane potential (V) was determined electronically and recorded also. Contractions after rest and at stimulation rates of 0.1, 0.25, 0.5, 1, 2, and 3 Hz were studied. With normal APs, isoflurane (1.3 and 2.5%) depressed peak tension significantly less at high frequencies than did equivalent doses of halothane (0.75 or 1.5%). Isoflurane depressed dT/dt max less than halothane at all frequencies. At 0.3 Hz stimulation, isoflurane (1-4%) significantly increased the normal AP duration by 7-11%. Slow calcium-dependent APs and accompanying contractions were studied in partially depolarized muscles (-40 to -45 mV resting potential in 26 mM K+ Tyrode's solution) stimulated with 0.1 microM isoproterenol. Following rest and at 0.1, 0.25, 0.5, 1, 2, and 3 Hz, both isoflurane (1.3% or 2.5%) and enflurane (1.7% or 3.5%) markedly depressed the late-peaking slow AP contraction observed with low-frequency stimulation. Halothane (0.75% or 1.5%) caused a similar contractile depression (40-60%) at all frequencies. In contrast, isoflurane depressed early peaking tension and the dT/dt max at frequencies greater than 1 Hz significantly less than did halothane or enflurane. At 0.3 Hz, 2% and 4% isoflurane caused 9% and 17% depression of slow AP maximum rate of depolarization (Vmax), but significantly prolonged the AP duration. Isoflurane altered the pattern of tension development in a different manner than halothane, suggesting differing mechanisms of myocardial depression by these anesthetics.

Volatile anesthetics depress Ca2+ transients and glutamate release in isolated cerebral synaptosomes

BACKGROUND

The current study was performed to determine whether volatile anesthetics may include as part of their action in the central nervous system the depression of presynaptic transmitter release by alteration in intrasynaptic [Ca2+] ([Ca2+]i).

METHODS

Guinea pig cerebrocortical synaptosomes were studied at 37 degrees C suspended in control buffer solution containing 1.3 mM external [Ca2+] ([Ca2+]e). Spectrofluorometric assays were used to monitor [Ca2+]i with the Ca(2+)-sensitive fluorophore Fura-2 and to monitor glutamate release with an enzyme-coupled assay that produced the fluorescent product nicotinamide adenine dinucleotide phosphate. To activate the increase in [Ca2+]i and glutamate release, synaptosomes were depolarized by abruptly increasing external [K+] from 5 to 35 mM. Responses were determined in solutions equilibrated with approximately 1 or 2 minimum alveolar concentration (MAC) isoflurane, enflurane, or halothane and also in solutions with decreased [Ca2+]e (0.025, 0.05, 0.1, 0.2, 0.4, and 0.6 mM).

RESULTS

Although they had no action on basal behavior, the anesthetics depressed the K(+)-depolarization-induced increase in both [Ca2+]i and glutamate release in a dose-dependent fashion. The [Ca2+]i transient was inhibited by 13-21% per MAC, and glutamate release was depressed 14-28% per MAC. The depression of both [Ca2+]i and glutamate release caused by 2.5% isoflurane, 3.4% enflurane, and 1.5% halothane could be reproduced by a reduction in [Ca2+]e to 0.2-0.4 mM.

CONCLUSIONS

In this setting, isoflurane, enflurane, and halothane decrease [Ca2+]i in a manner consistent with inhibition of Ca2+ entry, possibly by specific voltage-gated neuronal Ca2+ channels. This decrease in [Ca2+]i is sufficient to account for all or most of the associated decrease in glutamate release.

Effects of propofol and thiopental in isolated rat aorta and pulmonary artery

This study was performed to determine if direct arterial dilating actions of propofol contribute to the drug's hypotensive actions. The effects of propofol were compared with those of thiopental on isolated vascular ring preparations from rat thoracic aorta and pulmonary artery. Thoracic aortic ring responses were evaluated in the presence and absence of endothelium, indomethacin, and N omega-nitro-L-arginine methyl ester (LNAME; a specific inhibitor of endothelium-derived relaxing factor-nitric oxide [EDRF/NO] synthase). Pulmonary artery responses were investigated with intact endothelium. After the induction of active isometric force by a predetermined EC50 dose of phenylephrine for each ring, effects of propofol (30, 100, 300 microM) and thiopental (10, 30, 100 microM) were examined. Propofol caused significant vasodilation in endothelium-intact, endothelium-denuded, and LNAME-treated aortic rings. In the endothelium-intact aortic and pulmonary artery rings, the initial vasodilation due to 30 and 100 microM propofol showed gradual and partial recovery over 15 min; 300 microM propofol caused sustained vasodilation. Endothelium-denuded rings and LNAME-pretreated endothelium-intact rings showed constant and sustained vasodilation with all propofol concentrations. Propofol also caused marked vasodilation in pulmonary arteries. In contrast, thiopental had no vasodilating effect in aortic or pulmonary artery preparations. In control experiments, propofol vehicle (Intralipid) also had no effect on vascular rings. Indomethacin pretreatment induced a dose-dependent vasoconstriction by thiopental in endothelium-intact rings and decreased the vasodilation due to propofol.(ABSTRACT TRUNCATED AT 250 WORDS)

Illuminating gravitational waves: A concordant picture of photons from a neutron star merger

Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.

The effects of growth hormone and IGF-1 deficiency on cerebrovascular and brain ageing

Research studies clearly indicate that age-related changes in cellular and tissue function are linked to decreases in the anabolic hormones, growth hormone and insulin-like growth factor (IGF)-1. Although there has been extensive research on the effects of these hormones on bone and muscle mass, their effect on cerebrovascular and brain ageing has received little attention. We have also observed that in response to moderate calorie restriction (a treatment that increases mean and maximal lifespan by 30-40%), age-related decreases in growth hormone secretion are ameliorated (despite a decline in plasma levels of IGF-1) suggesting that some of the effects of calorie restriction are mediated by modifying the regulation of the growth hormone/IGF-1 axis. Recently, we have observed that microvascular density on the surface of the brain decreases with age and that these vascular changes are ameliorated by moderate calorie restriction. Analysis of cerebral blood flow paralleled the changes in vasculature in both groups. Administration of growth hormone for 28 d was also found to increase microvascular density in aged animals and further analysis indicated that the cerebral vasculature is an important paracrine source of IGF-1 for the brain. In subsequent studies, administration of GHRH (to increase endogenous release of growth hormone) or direct administration of IGF-I was shown to reverse the age-related decline in spatial working and reference memory. Similarly, antagonism of IGF-1 action in the brains of young animals impaired both learning and reference memory. Investigation of the mechanisms of action of IGF-1 suggested that this hormone regulates age-related alterations in NMDA receptor subtypes (e.g. NMDAR2A and R2B). The beneficial role of growth hormone and IGF-1 in ameliorating vascular and brain ageing are counterbalanced by their well-recognised roles in age-related pathogenesis. Although research in this area is still evolving, our results suggest that decreases in growth hormone and IGF-1 with age have both beneficial and deleterious effects. Furthermore, part of the actions of moderate calorie restriction on tissue function and lifespan may be mediated through alterations in the growth hormone/IGF-1 axis.