M-type potassium currents differentially affect activation of motoneuron subtypes and tune recruitment gain.

The size principle is a key mechanism governing the orderly recruitment of motor units and is believed to be dependent on passive properties of the constituent motoneurons. However, motoneurons are endowed with voltage-sensitive ion channels that create non-linearities in their input-output functions. Here we describe a role for the M-type potassium current, conducted by KCNQ channels, in the control of motoneuron recruitment in mice. Motoneurons were studied with whole-cell patch clamp electrophysiology in transverse spinal slices and identified based on delayed (fast) and immediate (slow) onsets of repetitive firing. M-currents were larger in delayed compared to immediate firing motoneurons, which was not reflected by variations in the presence of Kv7.2 or Kv7.3 subunits. Instead, a more depolarized spike threshold in delayed-firing motoneurons afforded a greater proportion of the total M-current to become activated within the subthreshold voltage range, which translated to a greater influence on their recruitment with little influence on their firing rates. Pharmacological activation of M-currents also influenced motoneuron recruitment at the population level, producing a rightward shift in the recruitment curve of monosynaptic reflexes within isolated mouse spinal cords. These results demonstrate a prominent role for M-type potassium currents in regulating the function of motor units, which occurs primarily through the differential control of motoneuron subtype recruitment. More generally, these findings highlight the importance of active properties mediated by voltage-sensitive ion channels in the differential control of motoneuron recruitment, which is a key mechanism for the gradation of muscle force. KEY POINTS: M-currents exert an inhibitory influence on spinal motor output. This inhibitory influence is exerted by controlling the recruitment, but not the firing rate, of high-threshold fast-like motoneurons, with limited influence on low-threshold slow-like motoneurons. Preferential control of fast motoneurons may be linked to a larger M-current that is activated within the subthreshold voltage range compared to slow motoneurons. Larger M-currents in fast compared to slow motoneurons are not accounted for by differences in Kv7.2 or Kv7.3 channel composition. The orderly recruitment of motoneuron subtypes is shaped by differences in the contribution of voltage-gated ion channels, including KCNQ channels. KCNQ channels may provide a target to dynamically modulate the recruitment gain across the motor pool and readily adjust movement vigour.

Natural killer cell receptors regulate responses of HLA-E-restricted T cells.

Human cytomegalovirus (CMV) infection can stimulate robust human leukocyte antigen (HLA)-E-restricted CD8+ T cell responses. These T cells recognize a peptide from UL40, which differs by as little as a single methyl group from self-peptides that also bind HLA-E, challenging their capacity to avoid self-reactivity. Unexpectedly, we showed that the UL40/HLA-E T cell receptor (TCR) repertoire included TCRs that had high affinities for HLA-E/self-peptide. However, paradoxically, lower cytokine responses were observed from UL40/HLA-E T cells bearing TCRs with high affinity for HLA-E. RNA sequencing and flow cytometric analysis revealed that these T cells were marked by the expression of inhibitory natural killer cell receptors (NKRs) KIR2DL1 and KIR2DL2/L3. On the other hand, UL40/HLA-E T cells bearing lower-affinity TCRs expressed the activating receptor NKG2C. Activation of T cells bearing higher-affinity TCRs was regulated by the interaction between KIR2D receptors and HLA-C. These findings identify a role for NKR signaling in regulating self/non-self discrimination by HLA-E-restricted T cells, allowing for antiviral responses while avoiding contemporaneous self-reactivity.

Is It Safe to Re-Harvest the Anterior Iliac Crest to Manage Le Fort I Interpositional Defects in Young Adults With a Repaired Cleft?

PURPOSE: Re-harvesting the anterior iliac crest to obtain autogenous bone grafts is a controversial practice. The purpose of this study was to assess the feasibility and associated disability of re-harvesting the anterior iliac crest. MATERIAL AND METHODS: To address the research purpose, the authors executed a retrospective case series study. The sample consisted of young adult patients with cleft (<26 yr old) with prior harvesting of the anterior iliac crest during mixed dentition for management of an alveolar cleft(s) and then re-harvesting of the same donor site for management of interpositional defects after Le Fort I advancement. Wound-healing parameters were reviewed at the donor and recipient sites. A survey questionnaire was provided after completion of treatment to document patient perception of early and any long-term donor-site disability. Descriptive statistics were computed for the variables. RESULTS: The sample was composed of 27 patients with a mean age at re-harvesting of 17 years (range, 14 to 25 yr). Patients underwent on average 7.4-mm horizontal advancement, 2.4-mm lengthening, and 2.6-mm transverse expansion of the maxilla. Adequate bone graft was re-harvested to accomplish objectives in all cases. There were no perioperative complications at the donor or recipient sites. Twenty-six of the 27 patients (97%) had fewer donor-site recovery difficulties at the time of re-harvesting compared with the first time graft was taken. There were no cases of lateral femoral cutaneous nerve injury and no long-term discomfort with walking, running, or other activities. CONCLUSIONS: The study confirms the safety and efficacy of re-harvesting corticocancellous bone from the anterior iliac crest for management of interpositional defects associated with Le Fort I advancement in young adults with a repaired cleft.

The development and initial validation of a new measure of male body dissatisfaction.

The purpose of this research was to develop, and establish the initial psychometric properties of, the Male Body Dissatisfaction Scale (MBDS). Ninety-five male students were recruited over three phases. An item-remainder analysis was performed in phase I, convergent and discriminant validity assessed in phase II, and test-retest reliability and factor structure assessed in phase III. The MBDS achieved an alpha level of 0.93 and was inversely related to body esteem (p=0.02) and self-esteem (p=0.03), and positively related to how much participants' opinion of themselves was based on their body shape and weight (p<0.01). The MBDS was not related to measures of affect, and was able to distinguish between males endorsing, and not endorsing, elevated body shape and weight concerns (p<0.05). Finally, the MBDS displayed a test-retest reliability coefficient of 0.96 (p<0.01). Findings suggest that the MBDS may fill the need for a reliable and valid measure of body dissatisfaction that allows men to weight particular aspects of their body image according to personal importance.