A study of cortical and brainstem mechanisms of diffuse noxious inhibitory controls in anaesthetised normal and neuropathic rats

Diffuse noxious inhibitory controls (DNIC) are a mechanism of endogenous descending pain modulation and are deficient in a large proportion of chronic pain patients. However, the pathways involved remain only partially determined with several cortical and brainstem structures implicated. This study examined the role of the dorsal reticular nucleus (DRt) and infralimbic (ILC) region of the medial prefrontal cortex in DNIC. In vivo electrophysiology was performed to record from dorsal horn lamina V/VI wide dynamic range neurones with left hind paw receptive fields in anaesthetised sham‐operated and L5/L6 spinal nerve‐ligated (SNL) rats. Evoked neuronal responses were quantified in the presence and absence of a conditioning stimulus (left ear clamp). In sham rats, DNIC were reproducibly recruited by a heterotopically applied conditioning stimulus, an effect that was absent in neuropathic rats. Intra‐DRt naloxone had no effect on spinal neuronal responses to dynamic brush, punctate mechanical, evaporative cooling and heat stimuli in sham and SNL rats. In addition, intra‐DRt naloxone blocked DNIC in sham rats, but had no effect in SNL rats. Intra‐ILC lidocaine had no effect on spinal neuronal responses to dynamic brush, punctate mechanical, evaporative cooling and heat stimuli in sham and SNL rats. However, differential effects were observed in relation to the expression of DNIC; intra‐ILC lidocaine blocked activation of DNIC in sham rats but restored DNIC in SNL rats. These data suggest that the ILC is not directly involved in mediating DNIC but can modulate its activation and that DRt involvement in DNIC requires opioidergic signalling.     

Effects of ketamine and midazolam on resting state connectivity and comparison with ENIGMA connectivity deficit patterns in schizophrenia

Subanesthetic administration of ketamine is a pharmacological model to elicit positive and negative symptoms of psychosis in healthy volunteers. We used resting‐state pharmacological functional MRI (rsPhfMRI) to identify cerebral networks affected by ketamine and compared them to the functional connectivity (FC) in schizophrenia. Ketamine can produce sedation and we contrasted its effects with the effects of the anxiolytic drug midazolam. Thirty healthy male volunteers (age = 19–37 years) underwent a randomized, three‐way, cross‐over study consisting of three imaging sessions, with 48 hr between sessions. A session consisted of a control period followed by infusion of placebo or ketamine or midazolam. The ENIGMA rsfMRI pipeline was used to derive two long‐distance (seed‐based and dual‐regression) and one local (regional homogeneity, ReHo) FC measures. Ketamine induced significant reductions in the connectivity of the salience network (Cohen's d: 1.13 ± 0.28, p = 4.0 × 10^?3), auditory network (d: 0.67 ± 0.26, p = .04) and default mode network (DMN, d: 0.63 ± 0.26, p = .05). Midazolam significantly reduced connectivity in the DMN (d: 0.77 ± 0.27, p = .03). The effect sizes for ketamine for resting networks showed a positive correlation (r = .59, p = .07) with the effect sizes for schizophrenia‐related deficits derived from ENIGMA's study of 261 patients and 327 controls. Effect sizes for midazolam were not correlated with the schizophrenia pattern (r = ?.17, p = .65). The subtraction of ketamine and midazolam patterns showed a significant positive correlation with the pattern of schizophrenia deficits (r = .68, p = .03). RsPhfMRI reliably detected the shared and divergent pharmacological actions of ketamine and midazolam on cerebral networks. The pattern of disconnectivity produced by ketamine was positively correlated with the pattern of connectivity deficits observed in schizophrenia, suggesting a brain functional basis for previously poorly understood effects of the drug.     

Frequency of Automatic Stimulations in Responsive Vagal Nerve Stimulation in Patients With Refractory Epilepsy

BackgroundIn vagal nerve stimulation (VNS) therapy, the release of VNS model 106 (AspireSR) allowed for responsive VNS (rVNS). rVNS utilizes a cardiac-based seizure detection algorithm to detect seizure-induced tachycardia to trigger additional stimulation. There are some studies suggesting clinical benefits of rVNS over traditional VNS, but the performance and significance of autostimulation mode in clinical practice are poorly understood.ObjectivesTo assess the effect of initiation of rVNS therapy and altered stimulation settings on the number of daily stimulations and energy consumption in VNS therapy and to compare autostimulation performance in different epilepsy types.Materials and MethodsRetrospective follow-up of 30 patients with drug-resistant epilepsy treated with rVNS including 17 new implantations and 13 battery replaces at a single center in Finland. Our data consist of 208 different stimulation periods, that is, episodes with defined stimulation settings and both autostimulation and total stimulation performance-related data along with clinical follow-up.ResultsThe variation in autostimulation frequency was highly dependent on the duration of the OFF-time and autostimulation threshold (p < 0.05). There was a large additional effect of autostimulation mode on therapy time and energy consumption with longer OFF-times, but a minor effect with shorter OFF-times. Significantly more autostimulations were triggered in the temporal lobe and multifocal epilepsies than in extratemporal lobe epilepsies.ConclusionsThe initiation of autostimulation mode in VNS therapy increased the total number of stimulations. Shortening the OFF-time leads to a decreased number and share of automatic activations. Epilepsy type may affect autostimulation activity.     

Chemoradiation-Related Lymphopenia and Its Association with Survival in Patients with Squamous Cell Carcinoma of the Anal Canal

BackgroundAlthough treatment‐related lymphopenia (TRL) is common and associated with poorer survival in multiple solid malignancies, few data exist for anal cancer. We evaluated TRL and its association with survival in patients with anal cancer treated with chemoradiation (CRT).Materials and MethodsA retrospective analysis of 140 patients with nonmetastatic anal squamous cell carcinoma (SCC) treated with definitive CRT was performed. Total lymphocyte counts (TLC) at baseline and monthly intervals up to 12 months after initiating CRT were analyzed. Multivariable Cox regression analysis was performed to evaluate the association between overall survival (OS) and TRL, dichotomized by grade (G)4 TRL (<0.2k/μL) 2 months after initiating CRT. Kaplan‐Meier and log‐rank tests were used to compare OS between patients with versus without G4 TRL.ResultsMedian time of follow‐up was 55 months. Prior to CRT, 95% of patients had a normal TLC (>1k/μL). Two months after initiating CRT, there was a median of 71% reduction in TLC from baseline and 84% of patients had TRL: 11% G1, 31% G2, 34% G3, and 8% G4. On multivariable Cox model, G4 TRL at two months was associated with a 3.7‐fold increased risk of death. On log‐rank test, the 5‐year OS rate was 32% in the cohort with G4 TRL versus 86% in the cohort without G4 TRL.ConclusionTRL is common and may be another prognostic marker of OS in anal cancer patients treated with CRT. The association between TRL and OS suggests an important role of the host immunity in anal cancer outcomes.Implications for PracticeThis is the first detailed report demonstrating that standard chemoradiation (CRT) commonly results in treatment‐related lymphopenia (TRL), which may be associated with a poorer overall survival (OS) in patients with anal squamous cell carcinoma. The association between TRL and worse OS observed in this study supports the importance of host immunity in survival among patients with anal cancer. These findings encourage larger, prospective studies to further investigate TRL, its predictors, and its relationship with survival outcomes. Furthermore, the results of this study support ongoing efforts of clinical trials to investigate the potential role of immunotherapy in anal cancer.     

Articular Cartilage Vesicles Generate Calcium Pyrophosphate Dihydrate-Like Crystals in Vitro

Objective. To identify the morphology of a mineral-forming fraction of adult porcine hyaline articular cartilage digest and characterize the mineral it forms. Methods. Electron microscopy, Fourier transform infrared (FTIR) spectroscopy, x-ray microanalysis, compensated polarized light microscopy, and biochemical studies including ¹⁴C-labeled UDPG pyrophosphohydrolase radiometric assay. Results. This fraction of articular cartilage digest contained membrane-limited vesicles resembling growth plate cartilage matrix vesicles and formed mineral after only 24 hours in physiologic salt solution containing 1 mM ATP. The mineral contained inorganic pyrophosphate, 95% of which derived from ATP, and phosphate, 93% of which derived from inorganic phosphate in the medium. The FTIR spectrum of this mineral closely resembled the spectrum of standard calcium pyrophosphate dihydrate (CPPD) crystals. Compensated polarized light microscopy showed positively birefringent, rod-shaped crystals morphologically identical to CPPD. Ca:P ratios, defined by energy-dispersive microanalysis, were also consistent with CPPD. Conclusion. The articular cartilage vesicle fraction of porcine hyaline cartilage is capable of generating mineral that strongly resembles CPPD.     

Synthesis of methanediol [CH2(OH)2]: The simplest geminal diol

Geminal diols—organic molecules carrying two hydroxyl groups at the same carbon atom—have been recognized as key reactive intermediates by the physical (organic) chemistry and atmospheric science communities as fundamental transients in the aerosol cycle and in the atmospheric ozonolysis reaction sequence. Anticipating short lifetimes and their tendency to fragment to water plus the aldehyde or ketone, free geminal diols represent one of the most elusive classes of organic reactive intermediates. Here, we afford an exceptional glance into the preparation of the previously elusive methanediol [CH₂(OH)₂] transient—the simplest geminal diol—via energetic processing of low-temperature methanol–oxygen ices. Methanediol was identified in the gas phase upon sublimation via isomer-selective photoionization reflectron time-of-flight mass spectrometry combined with isotopic substitution studies. Electronic structure calculations reveal that methanediol is formed via excited state dynamics through insertion of electronically excited atomic oxygen into a carbon–hydrogen bond of the methyl group of methanol followed by stabilization in the icy matrix. The first preparation and detection of methanediol demonstrates its gas-phase stability as supported by a significant barrier hindering unimolecular decomposition to formaldehyde and water. These findings advance our perception of the fundamental chemistry and chemical bonding of geminal diols and signify their role as an efficient sink of aldehydes and ketones in atmospheric environments eventually coupling the atmospheric chemistry of geminal diols and Criegee intermediates.

Since the turn of the century, geminal diols—defined as organic molecules carrying two hydroxyl groups (OH) at the same carbon atom—have been recognized as key reactive intermediates by the physical (organic) chemistry and atmospheric science communities as fundamental transients in the aerosol cycle (1–3). However, even the simplest representative of a geminal diol—methanediol [CH₂(OH)₂] (1′, 1″)—has not been isolated yet and is conjectured only to exist as short-lived intermediates in the troposphere and in aqueous solutions of formaldehyde (H₂CO) as a transient driven by the inherent dehydration tendency and instability of the two adjacent hydroxyl groups at the same carbon atom (4–7). This classifies geminal diols as one of the least-explored classes of organic reactive intermediates.Gas-phase electronic structure calculations predict that two conformers of methanediol [CH₂(OH)₂] (1′, 1″) are thermodynamically favorable compared to the well-known methyl peroxide isomer (CH₃OOH, 2) by 267 kJ ⋅ mol⁻¹ and 257 kJ ⋅ mol⁻¹, respectively; these conformers are also thermodynamically and kinetically stable toward unimolecular decomposition via dehydration to the formaldehyde–water complex (3), as the 1′ to 3 and 1″ to 3 reactions are endoergic by 21 and 11 kJ ⋅ mol⁻¹ and have barriers of 181 and 191 kJ ⋅ mol⁻¹, respectively (8–11) (Fig. 1). A second decomposition mechanism of 1′/1″ to formic acid (HCOOH) and molecular hydrogen (H₂) involves a transition state predicted to be even 159 kJ ⋅ mol⁻¹ higher than the barrier of the dehydration mechanism (12). Consequently, methanediol [CH₂(OH)₂] (1′, 1″) is expected to be thermodynamically and kinetically stable and hence should be detectable in the gas phase once prepared. However, envisaging the complexities of a directed gas-phase synthesis and short lifetimes of these reactive intermediates, free geminal diols signify one of the most elusive groups of organic transient molecules. This system is also attractive from the viewpoint of electronic structure theory and chemical bonding to benchmark the chemical reactivity and fundamental bond-breaking processes leading to geminal diols in extreme environments.Open in a separate windowFig. 1.Molecular structures of CH₄O₂ isomers. Relative energies, point groups, electronic ground states, and adiabatic ionization energies (blue) of CH₄O₂ isomers are also compiled. The energies were computed at the coupled cluster singles, doubles, and perturbative triples level with a complete basis set extrapolation [CCSD(T)/CBS] and include zero-point vibrational energy corrections. The atoms are color coded in gray (carbon), white (hydrogen), and red (oxygen). The formation of methanediol [(CH₂(OH)₂], 1’ and 1’’) and methyl peroxide (CH₃OOH, 2) via excited-state oxygen atom [O(¹D)] insertion into a carbon–hydrogen and carbon–oxygen/oxygen–hydrogen bonds of methanol (CH₃OH), respectively, are barrierless. The transition state of the decomposition of methanediol [(CH₂(OH)₂], 1’ and 1’’) to a formaldehyde (H₂CO) and water (H₂O) complex (H₂CO···H₂O, 3) is also shown.Here, we report the very first preparation of the previously elusive methanediol [CH₂(OH)₂] molecule (1’), along with its isomer methyl peroxide isomer (CH₃OOH) (2), through exposure of low-temperature (5 K) methanol (CH₃OH)–oxygen (O₂) ices to energetic electrons (SI Appendix, Tables S1–S4). The isomers were unambiguously identified in the gas phase upon sublimation in the temperature-programmed desorption (TPD) phase and discriminated through isomer-selective photoionization–reflectron time-of-flight mass spectrometry together with mass shifts of their isotopically substituted counterparts. The identification of the simplest geminal diol 1’ may have far-reaching consequences for the atmospheric chemistry. Thermodynamically and kinetically stable geminal diols may “lock up” aldehydes and ketones—formed as byproducts of the Criegee-intermediate formation reaction—as geminal diols and hence would remove carbonyl compounds from the atmospheric ozonolysis reaction sequence (1, 13, 14). The Criegee-intermediate formation reaction is a process in which ozone reacts with alkenes forming a carbonyl oxide with two charge centers (Criegee intermediate) (14). Therefore, the existence of geminal diols and Criegee intermediates couples the chemistries of geminal diols, carbonyl compounds, and Criegee intermediates, thus helping to provide a better understanding of the atmospheric chemistry upon which all terrestrial life depends.