Sleep spindles and human cortical nociception: a surface and intracerebral electrophysiological study

Key points

• Sleep spindle are usually considered to play a major role in inhibiting sensory inputs.
• Using nociceptive stimuli in humans, we tested the effect of spindles on behavioural, autonomic and cortical responses in two experiments using surface and intracerebral electroencephalographic recordings.
• We found that sleep spindles do not prevent arousal reactions to nociceptive stimuli and that autonomic reactivity to nociceptive inputs is not modulated by spindle activity.
• Moreover, neither the surface sensory, nor the insular evoked responses were modulated by the spindle, as detected at the surface or within the thalamus.
• The present study comprises the first investigation of the effect of spindles on nociceptive information processing and the results obtained challenge the classical inhibitory effect of spindles.

Abstract

Responsiveness to environmental stimuli declines during sleep, and sleep spindles are often considered to play a major role in inhibiting sensory inputs. In the present study, we tested the effect of spindles on behavioural, autonomic and cortical responses to pain, in two experiments assessing surface and intracerebral responses to thermo‐nociceptive laser stimuli during the all‐night N2 sleep stage. The percentage of arousals remained unchanged as a result of the presence of spindles. Neither cortical nociceptive responses, nor autonomic cardiovascular reactivity were depressed when elicited within a spindle. These results could be replicated in human intracerebral recordings, where sleep spindle activity in the posterior thalamus failed to depress the thalamocortical nociceptive transmission, as measured by sensory responses within the posterior insula. Hence, the assumed inhibitory effect of spindles on sensory inputs may not apply to the nociceptive system, possibly as a result of the specificity of spinothalamic pathways and the crucial role of nociceptive information for homeostasis. Intriguingly, a late scalp response commonly considered to reflect high‐order stimulus processing (the ‘P3’ potential) was significantly enhanced during spindling, suggesting a possible spindle‐driven facilitation, rather than attenuation, of cortical nociception.

Abbreviations

AASM

American Academy of Sleep Medicine

EKG

electrocardiogram

EMG

electromyogram

EOG

electrooculogram

LEP

laser‐evoked potentials

MNI

Montreal Neurological Institute

MRI

magnetic resonance imaging

REM

rapid eye movement

SEEG

stereo‐electroencephalography

     

Melatonin in vivo prolongs cardiac allograft survival in rats

Melatonin, secreted by the pineal gland, is a multifunctional agent which (i) protects tissues from damage through free radical scavenging and attenuates ischemia/reperfusion injury in organ grafts; (ii) acts synergistically with cellular antioxidants; and (iii) displays complex, dose-dependent immunoenhancing and suppressing effects in vitro and in vivo. We analyzed the immunomodulatory effect of melatonin on acute allograft rejection. Cardiac grafts were transplanted from LBNF1 to LEW rats and anastomosed to the abdominal great vessels. The effect of low-dose (LD; 20 mg/kg/day) and high-dose (HD; 200 mg/kg/day) melatonin treatment in recipients compared with untreated controls was investigated. HD melatonin therapy abrogated acute rejection, significantly prolonging allograft survival (mean survival: 12.3 +/- 1 days S.D., n = 8, P < 0.0001) compared with untreated controls, which rapidly reject the transplant (6.3 +/- 1 days n = 12). LD therapy did not extend survival significantly (7.3 +/- 1.1 days, n = 12). Allospecific IgM showed a significant decrease in animals receiving HD therapy versus untreated recipients at days 10 and 14 post-transplantation (P < 0.01), whereas in the LD group at day 10, a significant increase in allospecific IgM (P < 0.01) over the HD cohort was demonstrated. HD treatment markedly reduced lymphocyte proliferative capacity compared with controls and the LD group. HD melatonin treatment abrogated acute allograft rejection and significantly prolonged graft survival. Our results suggest an involvement of melatonin in humoral and cellular immune pathways following perfused organ transplantation. These findings may indicate a novel therapeutic approach, based on modulation of the neuroendocrine/immune axis through melatonin as a possible future immunosuppressant in organ transplantation.     

Characteristic cardiac phenotypes are detected by cardiovascular magnetic resonance in patients with different clinical phenotypes and genotypes of mitochondrial myopathy

Background

Mitochondrial myopathies (MM) are a heterogeneous group of inherited conditions resulting from a primary defect in the mitochondrial respiratory chain with consecutively impaired cellular energy metabolism. Small sized studies using mainly electrocardiography (ECG) and echocardiography have revealed cardiac abnormalities ranging from conduction abnormalities and arrhythmias to hypertrophic or dilated cardiomyopathy in these patients. Recently, characteristic patterns of cardiac involvement were documented by cardiovascular magnetic resonance (CMR) in patients with chronic progressive external ophthalmoplegia (CPEO)/Kearns-Sayre syndrome (KSS) and with mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS). The present study aimed to characterize the prevalence and pattern of cardiac abnormalities and to test the additional diagnostic value of CMR in this patient population. The hypothesis that different neuromuscular MM syndromes present with different cardiac disease phenotypes was evaluated.

Methods

Sixty-four MM patients (50 ± 15 years, 44 % male) and 25 matched controls (52 ± 14 years, 36 % male) prospectively underwent cardiac evaluations including CMR (comprising cine- and late-gadolinium-enhancement (LGE) imaging). Based on the neuromuscular phenotype and genotype, the patients were grouped: a) CPEO/KSS (N = 33); b) MELAS/–like (N = 11); c) myoclonic epilepsy with ragged-red fibers (MERRF) (N = 3) and d) other non-specific MM forms (N = 17).

Results

Among the 64 MM patients, 34 (53 %) had at least one abnormal CMR finding: 18 (28 %) demonstrated an impaired left ventricular ejection-fraction (LV-EF <60 %), 14 (22 %) had unexplained LV hypertrophy and 21 (33 %) were LGE-positive. Compared to controls, MM patients showed significantly higher maximal wall thickness (10 ± 3 vs. 8 ± 2 mm, p = 0.005) and concentricity (LV mass to end-diastolic volume: 0.84 ± 0.27 vs. 0.67 ± 0.11, p < 0.0001) with frequent presence of non-ischemic LGE (30 % vs. 0 %, p = 0.001). CPEO/KSS showed a predominantly intramural pattern of LGE mostly confined to the basal LV inferolateral wall (8/10; 80 %) in addition to a tendency toward concentric remodelling. MELAS/-like patients showed the highest frequency of cardiac disease (in 10/11 (91 %)), a mostly concentric LV hypertrophy (6/9; 67 %) with or without LV systolic dysfunction and a predominantly focal, patchy LGE equally distributed among LV segments (8/11; 73 %). Patients with MERRF and non-specific MM had no particular findings. Pathological CMR findings indicating cardiac involvement were detected significantly more often than pathological ECG results or elevated cardiac serum biomarkers (34 (53 %) vs. 18 (28 %) vs. 21 (33 %); p = 0.008).

Conclusion

Cardiac involvement is a frequent finding in MM patients – and particularly present in KSS/CPEO as well as MELAS/-like patients. Despite a high variability in clinical presentation, CPEO/KSS patients typically show an intramural pattern of LGE in the basal inferolateral wall whereas MELAS patients are characterized by overt concentric hypertrophy and a rather unique, focally accentuated and diffusely distributed LGE.

Electronic supplementary material

The online version of this article (doi:10.1186/s12968-015-0145-x) contains supplementary material, which is available to authorized users.     

Granzyme B delivery via perforin is restricted by size, but not by heparan sulfate-dependent endocytosis

How granzymes gain entry into the cytosol of target cells during killer cell attack has been the subject of several studies in the past, but the effective delivery mechanism during target cell encounter has not been clarified. Here we show that granzyme B (GzmB) mutants lacking binding to negatively charged, essentially heparan-sulfate-containing membrane receptors are poorly endocytosed yet are delivered to the cytosol with efficacy similar to that of WT GzmB. In a cell-based system GzmB-deficient natural killer cells provided perforin (pfn) by natural polarized secretion and synergized with externally added GzmB. Whereas receptor (heparan sulfate)-dependent endocytosis was dispensable, delivery of larger cargo like that of GzmB fusion proteins and GzmB–antibody complexes was restricted by their size. Our data support the model in which granzymes are primarily translocated through repairable membrane pores of finite size and not by the disruption of endocytosed vesicles. We conclude that structurally related translocators, i.e., perforin and cholesterol-dependent cytolysins, deliver deathly cargo across host cell membranes in a similar manner.     

MinD-like ATPase FlhG effects location and number of bacterial flagella during C-ring assembly

The number and location of flagella, bacterial organelles of locomotion, are species specific and appear in regular patterns that represent one of the earliest taxonomic criteria in microbiology. However, the mechanisms that reproducibly establish these patterns during each round of cell division are poorly understood. FlhG (previously YlxH) is a major determinant for a variety of flagellation patterns. Here, we show that FlhG is a structural homolog of the ATPase MinD, which serves in cell-division site determination. Like MinD, FlhG forms homodimers that are dependent on ATP and lipids. It interacts with a complex of the flagellar C-ring proteins FliM and FliY (also FliN) in the Gram-positive, peritrichous-flagellated Bacillus subtilis and the Gram-negative, polar-flagellated Shewanella putrefaciens. FlhG interacts with FliM/FliY in a nucleotide-independent manner and activates FliM/FliY to assemble with the C-ring protein FliG in vitro. FlhG-driven assembly of the FliM/FliY/FliG complex is strongly enhanced by ATP and lipids. The protein shows a highly dynamic subcellular distribution between cytoplasm and flagellar basal bodies, suggesting that FlhG effects flagellar location and number during assembly of the C-ring. We describe the molecular evolution of a MinD-like ATPase into a flagellation pattern effector and suggest that the underappreciated structural diversity of the C-ring proteins might contribute to the formation of different flagellation patterns.Most bacteria move by flagella. The flagellar architecture is conserved and can be divided into the cytoplasmic C-ring, the basal body, the rod, and the exterior hook and filament structures (1). Bacterial species differ in the number and arrangement of their flagella (flagellation pattern) (2). However, the mechanisms that allow bacteria to establish their specific flagellation patterns reproducibly during each cell division are poorly understood. The protein FlhG (also known as “YlxH,” “MinD2,” “FleN,” or “MotR”) is essential for the correct flagellation pattern of polar- (3–5), lophotrichous- (6), amphitrichous- (7), and peritrichous-flagellated bacteria (8, 9). Deletion of flhG in polar-flagellated bacteria leads to hyperflagellation and impaired motility (3–5). In the amphitrichous-flagellated Campylobacter jejuni, ∼40% of the cells of a ΔflhG strain exhibited more than one flagellum at one pole and were impaired in motility (7). The peritrichous-flagellated bacterium Bacillus subtilis exhibits ∼26 flagellar basal bodies arranged symmetrically around midcell in a gridlike pattern (8). Furthermore, flagella are discouraged at the cell pole. Deletion of flhG does not result in swimming or swarming defects, although multiple flagella appear in tufts from constrained loci on the cell, and flagellar basal bodies often are aggregated (8). FlhG acts in concert with the signal recognition particle (SRP)-GTPase FlhF (10–14) that recruits the flagellar protein FliF to the cell pole in the polar-flagellated Vibrio cholerae (15). FlhG is predicted to belong to the MinD/ParA ATPase family (6, 16) whose characterized members act in orchestrated spatiotemporal processes (e.g., cell-division site determination and plasmid/chromosome partitioning (summarized in ref. 17). Together with MinC, MinD constitutes the conserved center of the Min system which regulates bacterial cell division by restricting cytokinetic Z-ring assembly to midcell (reviewed in ref. 18). MinD forms ATP-dependent homodimers (19) that interact with the inner membrane through a C-terminal amphipathic helix (membrane-targeting sequence, MTS) (20, 21). By this mechanism, MinD recruits MinC to the membrane where MinC inhibits polymerization of FtsZ into the Z-ring (22). Interestingly, Campylobacter jejuni does not contain a Min system, and FlhG is involved in flagellation pattern control and regulation of cell division (7). In contrast to MinD, the molecular framework in which the putative MinD-like ATPase FlhG controls flagellation is unknown. Also, it is enigmatic how conserved homologs of FlhG can control different flagellation patterns in different species. Here, we investigated the mechanism and function of FlhG in the Gram-positive, peritrichous-flagellated B. subtilis (Bs) and the Gram-negative, polar-flagellated Shewanella putrefaciens (Sp).     

Histomorphometric Assessment of Cancellous and Cortical Bone Material Distribution in the Proximal Humerus of Normal and Osteoporotic Individuals: Significantly Reduced Bone Stock in the Metaphyseal and Subcapital Regions of Osteoporotic Individuals

Osteoporosis is a systemic disorder predominantly affecting postmenopausal women but also men at an advanced age. Both genders may suffer from low-energy fractures of, for example, the proximal humerus when reduction of the bone stock or/and quality has occurred.The aim of the current study was to compare the amount of bone in typical fracture zones of the proximal humerus in osteoporotic and non-osteoporotic individuals.The amount of bone in the proximal humerus was determined histomorphometrically in frontal plane sections. The donor bones were allocated to normal and osteoporotic groups using the T-score from distal radius DXA measurements of the same extremities. The T-score evaluation was done according to WHO criteria. Regional thickness of the subchondral plate and the metaphyseal cortical bone were measured using interactive image analysis.At all measured locations the amount of cancellous bone was significantly lower in individuals from the osteoporotic group compared to the non-osteoporotic one. The osteoporotic group showed more significant differences between regions of the same bone than the non-osteoporotic group. In both groups the subchondral cancellous bone and the subchondral plate were least affected by bone loss. In contrast, the medial metaphyseal region in the osteoporotic group exhibited higher bone loss in comparison to the lateral side.This observation may explain prevailing fracture patterns, which frequently involve compression fractures and certainly has an influence on the stability of implants placed in this medial region. It should be considered when planning the anchoring of osteosynthesis materials in osteoporotic patients with fractures of the proximal humerus.