Comparison of rhythmic jaw muscle activities induced by electrical stimulations of the corticobulbar tract during rapid eye movement sleep with those during wakefulness and non-rapid eye movement sleep in freely moving guinea pigs.

OBJECTIVE: Rhythmic jaw muscle activities (RJMAs) occur during rapid eye movement (REM) sleep in humans and animals even though motoneurons are inhibited. The present study compared the characteristics of jaw muscle activities induced by electrical microstimulations of the corticobulbar tract (CT) during REM sleep with those during wakefulness and non-REM sleep. METHODS: Eleven guinea pigs were surgically prepared for polygraphic recordings with the implantation of a stimulating electrode. Long- and short-train repetitive electrical microstimulations were applied to the CT under freely moving conditions. The response rate, latency, burst amplitude, and cycle length in the digastric muscle were calculated and cortical and cardiac activities were quantified. RESULTS: Long-train microstimulations induced RJMAs in the digastric muscle followed by masseter muscle activity during wakefulness and non-REM sleep and only induced rhythmic digastric muscle activity during REM sleep. The response rate of RJMAs and the burst amplitude of digastric muscles were significantly lower during REM sleep than during wakefulness and non-REM sleep. However, response latency did not significantly differ between REM sleep and wakefulness. Transient cortical and cardiac changes were associated with RJMAs induced during non-REM sleep, but not during REM sleep. Short-train microstimulations induced a short-latency digastric response, the amplitude of which was significantly lower during REM sleep than during non-REM sleep and wakefulness. CONCLUSIONS: These results suggest that the masticatory CPG was activated by electrical CT stimulations independently of the motoneuron inhibitory system during REM sleep.

Rev1 overexpression accelerates N-methyl-N-nitrosourea (MNU)-induced thymic lymphoma by increasing mutagenesis.

Rev1 has two important functions in the translesion synthesis pathway, including dCMP transferase activity, and acts as a scaffolding protein for other polymerases involved in translesion synthesis. However, the role of Rev1 in mutagenesis and tumorigenesis in vivo remains unclear. We previously generated Rev1-overexpressing (Rev1-Tg) mice and reported that they exhibited a significantly increased incidence of intestinal adenoma and thymic lymphoma (TL) after N-methyl-N-nitrosourea (MNU) treatment. In this study, we investigated mutagenesis of MNU-induced TL tumorigenesis in wild-type (WT) and Rev1-Tg mice using diverse approaches, including whole-exome sequencing (WES). In Rev1-Tg TLs, the mutation frequency was higher than that in WT TL in most cases. However, no difference in the number of nonsynonymous mutations in the Catalogue of Somatic Mutations in Cancer (COSMIC) genes was observed, and mutations involved in Notch1 and MAPK signaling were similarly detected in both TLs. Mutational signature analysis of WT and Rev1-Tg TLs revealed cosine similarity with COSMIC mutational SBS5 (aging-related) and SBS11 (alkylation-related). Interestingly, the total number of mutations, but not the genotypes of WT and Rev1-Tg, was positively correlated with the relative contribution of SBS5 in individual TLs, suggesting that genetic instability could be accelerated in Rev1-Tg TLs. Finally, we demonstrated that preleukemic cells could be detected earlier in Rev1-Tg mice than in WT mice, following MNU treatment. In conclusion, Rev1 overexpression accelerates mutagenesis and increases the incidence of MNU-induced TL by shortening the latency period, which may be associated with more frequent DNA damage-induced genetic instability.

Ability to control directional lip-closing force in skeletal class III patients.

BACKGROUND: The relationship between the maximum lip-closing force (LCF) and malocclusion has long been studied. Recently, a method to measure the ability to control directional LCF from eight directions (upper, lower, right, left and the four directions in between) during lip pursing was established. OBJECTIVE: It is considered important to evaluate the ability to control directional LCF. The aim of this study was to investigate the ability of skeletal class III patients to control directional LCF. METHODS: Fifteen skeletal class III patients (mandibular prognathism group) and 15 people with normal occlusion (normal occlusion group) were recruited. The maximum LCF and the accuracy rate (the ratio of the matched time in which the participant was able to keep the LCF in the target range over a total time of 6 s) were measured. RESULTS: The maximum LCF was not significantly different between the mandibular prognathism group and the normal occlusion group. The accuracy rate in the mandibular prognathism group was significantly lower in all six directions than that in the individual normal occlusion group. CONCLUSION: As the accuracy rate in all six directions was significantly lower in the mandibular prognathism group than that in the normal occlusion group, occlusion and craniofacial morphology might influence lip function.

Novel mechanisms for the removal of strong replication-blocking HMCES- and thiazolidine-DNA adducts in humans.

Apurinic/apyrimidinic (AP) sites are DNA lesions created under normal growth conditions that result in cytotoxicity, replication-blocks, and mutations. AP sites are susceptible to ß-elimination and are liable to be converted to DNA strand breaks. HMCES (5-hydroxymethylcytosine binding, ES cell specific) protein interacts with AP sites in single stranded (ss) DNA exposed at DNA replication forks to generate a stable thiazolidine protein-DNA crosslink and protect cells against AP site toxicity. The crosslinked HMCES is resolved by proteasome-mediated degradation; however, it is unclear how HMCES-crosslinked ssDNA and the resulting proteasome-degraded HMCES adducts are processed and repaired. Here, we describe methods for the preparation of thiazolidine adduct-containing oligonucleotides and determination of their structure. We demonstrate that the HMCES-crosslink is a strong replication blocking adduct and that protease-digested HMCES adducts block DNA replication to a similar extent as AP sites. Moreover, we show that the human AP endonuclease APE1 incises DNA 5' to the protease-digested HMCES adduct. Interestingly, while HMCES-ssDNA crosslinks are stable, the crosslink is reversed upon the formation of dsDNA, possibly due to a catalytic reverse reaction. Our results shed new light on damage tolerance and repair pathways for HMCES-DNA crosslinks in human cells.

Longitudinal electromyographic analysis of jaw-closing muscle activities during ingestive behaviors from pre-weaning to juvenile periods in rats.

This longitudinal study investigated developmental changes in jaw-closing muscle activities during ingestive behaviors in rats. On postnatal day (P) 10, electromyography (EMG) electrodes were inserted into the masseter and temporalis muscles of rat pups. EMG activities were recorded for the following ingestive behaviors between P14 and P49: for suckling, including nipple attachment and rhythmic sucking on P14 and for pasta biting, pellet chewing, and milk licking between P21 and P49. Burst rhythms and muscle coordination (i.e., the correlation and time lag) between masseter and temporalis activities were assessed for each behavior. The burst rhythms of nipple attachment and rhythmic sucking on P14 were significantly slower than those of pasta biting, pellet chewing, and milk licking on P21. Muscle coordination differed between suckling on P14 and mastication and licking on P21. Between P21 and P49, increases were observed in burst rhythms for pasta biting and pellet chewing. The rate of increases in burst rhythms was higher for pasta biting than for pellet chewing. Muscle coordination between the two muscle activities for pasta biting did not significantly change between P21 and P49, whereas that for pellet chewing significantly changed between P21 and P24 and stabilized after P24. Burst rhythms for milk licking did not significantly change over time, while muscle coordination between the two muscle activities changed from agonist to antagonist muscle-like activity on approximately P35. The present results demonstrate that distinct patterns of rhythmic jaw-closing muscle activities emerge before weaning, they continue to change over time, and they exhibit unique developmental dynamics for each behavior after weaning.

Motor representation of rhythmic jaw movements in the amygdala of guinea pigs.

OBJECTIVE: The areas of the amygdala contributing to rhythmic jaw movements and the movement patterns induced remain unknown. Therefore, the present study investigated the areas of the amygdala contributing to rhythmic jaw movements using repetitive electrical microstimulation techniques. DESIGN: Experiments were performed on head-restrained guinea pigs under ketamine-xylazine anesthesia. EMG activities in the masseter and digastric muscles and jaw movements were recorded. Short- and long-train electrical microstimulations of the amygdala were performed and the patterns of jaw movements induced were analyzed quantitatively. RESULT: The short-train stimulation induced short-latency EMG responses in the masseter and/or digastric muscles. The stimulation sites inducing short-latency EMG responses were distributed within the ventral part of the amygdala, which covered the medial, basal, and cortical nuclei. The long-train stimulation induced tonic jaw opening and two types of rhythmic jaw movements: those with or without lateral jaw shifts, which were characterized by a larger jaw gape and ipsilateral jaw excursion, respectively. Rhythmic jaw movements with lateral jaw shifts were characterized by overlapping masseter and digastric EMG activities. However, rhythmic patterns did not differ between the two types of rhythmic jaw movements. The stimulation sites that induced rhythmic jaw movements were more localized to the cortical nucleus. CONCLUSIONS: The present results suggest that the ventral part of the amygdala is involved in the induction of rhythmic jaw movements in guinea pigs. The putative roles of the limbic system in the genesis of functional (e.g., chewing) and non-functional (e.g., bruxism) rhythmic oromotor movements warrant further study.

Evaluation of the usefulness of cystic duct three-dimensional computed tomography with non-contrast for before laparoscopic cholecystectomy and endoscopic transpapillary gallbladder drainage in comparison to magnetic resonance cholangiopancreatography.

INTRODUCTION: The purpose of this study is to evaluate whether anatomical variations of the cystic duct and accessory bile duct can be grasped by cystic duct three-dimensional (3D)-computed tomography (CT) using non-contrast CT and to examine the possibility of omitting magnetic resonance cholangiopancreatography (MRCP). METHODS: Of patients who underwent non-contrast abdominal CT between May and October 2019, those who underwent MRCP within 1 month before and afterwards were targeted. Seven assessors visually evaluated the cystic duct 3D-CT images on a 5-point scale. Average scores of ≥3 and <3 points were assigned as the good and poor groups, respectively. Regions of interest (ROIs) were placed inside the cystic duct and four places around it, and the CT values in those ROIs were measured. The CT value difference was calculated by subtracting the surrounding CT values from the CT value in the cystic duct and converting the result to an absolute value. The CT value difference was classified into good and poor groups, and statistical analysis was performed. Seven assessors evaluated anatomical variations of the cystic duct and the presence of the accessory bile duct. The results were compared with the MRCP interpretation results to calculate sensitivity, specificity, positive predictive value, and negative predictive value. RESULTS: The average visual evaluation score was 3.8. The good and poor groups were comprised by 53 (85.5%) and 9 (14.5%) patients, respectively. The CT difference value averages were 54.7 and 15.9 for the good and poor groups, respectively, and the value was significantly higher in the good group (p = 0.001). The comparison results with MRCP were sensitivity=83.3%, specificity=78.0%, positive predictive value=47.6%, and negative predictive value=95.1%. CONCLUSION: Cystic duct 3D-CT using non-contrast CT is a useful technique for understanding anatomical variations of the cystic duct and accessory bile duct. Our method may reduce the number of MRCP sessions performed.

Age-related differences in maximum voluntary lip-closing force and ability to control lip-closing force.

OBJECTIVES: Deterioration of lip function in the elderly is a form of oral hypofunction. It is important to understand age-related changes in lip function to improve oral health. This study aimed to quantitatively compare the maximum lip-closing force (LCF) and the ability to control LCF during voluntary lip-pursing movements between elderly and young adults and clarify the influence of aging on both measurements. METHODS: Using a multidirectional LCF measurement system, we measured six-directional maximum LCFs (upper, upper right, lower right, lower, lower left, upper right) of 20 healthy elderly men (69.6 ± 4.2 years) and 20 healthy young men (25.1 ± 3.8 years). The ability to control the LCF in each direction was assessed based on the accuracy rate. The directional LCF and the ability to control LCF were compared between the elderly and young adults. RESULTS: The maximum directional LCF in the elderly adults was significantly smaller than that in the young adults in three directions from the lower lip; moreover, the accuracy rate of the elderly adults was significantly lower than that of young adults in five of the six directions. CONCLUSIONS: Our findings suggest that the influence of aging on the accuracy of LCF may be different from that on muscle strength. Hypofunction of the lips due to aging may result not only from decreased muscle strength but also from reduced LCF accuracy.

Improvement of oral hypofunction by a comprehensive oral and physical exercise programme including textured lunch gatherings.

The deterioration of oral function to a state of oral hypofunction (OHF) is reportedly associated with malnutrition and frailty. Thus, we Investigated the association of OHF with physical characteristics and function and test the effects of a programme including comprehensive oral and physical exercises and textured lunch gatherings (COPE-TeL programme) on oral and physical function in older adults with OHF. Eighty-six community-dwelling older adults were randomly assigned into control (n = 43) or intervention (n = 43) groups. The participants were further divided into OHF and normal oral function (NOF) sub-groups based on initial oral examinations. The intervention group participated in the 12-week COPE-TeL programme, while the control group performed the physical exercise regimen only. The differences in measured variables for physical and oral function between the OHF and NOF groups were statistically tested, and changes in the proportion of participants with OHF were examined. Physical function, such as hand grip strength and walking speed, was significantly lower in the OHF group at the initial assessment. The proportion of participants with OHF was 56% in the intervention group and 67% in the control group before the trial, which became significantly reduced after completing the COPE-TeL programme in the intervention group (26%, P = .002), but not in the controls (61%, P = .549). Older adults with OHF may have diminished physical function. The COPE-TeL programme of oral and physical exercises along with textured lunch gatherings may be effective for older adults with OHF.

A novel approach for detection of functional expression of TRPV1 channels on regenerated neurons following nerve injury.

Transient receptor potential vanilloid 1 (TRPV1) is a polymodal receptor channel, which plays an important role in pain transduction. It is important to understand the functional expression of this channel under neuropathic pain (NP) conditions. A novel method was used to investigate the dynamics of functional expression of this channel on regenerated neurons under NP conditions following trigeminal nerve injury using a combination of a permanently charged sodium channel blocker (QX-314) and a TRPV1 agonist (capsaicin; QX-CAP). The combination was originally introduced as a local anesthetic. Synchronization between the local anesthetic effect of QX-CAP and TRPV1 expression on regenerated neurons was observed following the nerve injury. QX-CAP had no local anesthetic effect under NP conditions 2 weeks after the injury when TRPV1 expression on regenerated neurons was low. However, this combination was effective under NP conditions 3 and 4 weeks following injury when TRPV1 expression in regenerated neurons was moderate to high. The current review, discusses the potential of QX-314 as a local anesthetic and a novel approach of using QX-CAP to reveal the dynamics of functional expression of TRPV1 on regenerated neurons following trigeminal nerve injury.

Effects of textured foods on masticatory muscle activity in older adults with oral hypofunction.

BACKGROUND: Preserving sufficient oral function and maintaining proper nutrition are essential to prevent frailty. Thus, we have developed "munchy" foods that contain harder textures and are rich in protein. OBJECTIVES: This study aimed to test the effects of masticating textured foods on masticatory muscle activity in young and older adults. METHODS: Twenty young and 32 community-dwelling older individuals participated in this study. After measuring oral function, we subdivided the older participants into normal and oral hypofunction (OHF) groups. Two test foods (meatloaf and chicken ball) were prepared to have a harder texture using specific ingredients (munchy) or not (control). The participants ate 10 g of the test foods in random order while being measured for masseter muscle activity with a surface electromyogram (EMG). We calculated the number of chewing cycles and integrated muscle activity of the masseter muscle from the EMG data and tested for differences by food texture or age group. RESULTS: The number of chewing cycles, mean EMG amplitude and integrated EMG activity was significantly higher for the munchy foods than for the controls for all groups. The integrated masseter muscle EMG activity was significantly increased in the normal older group than in the young group for both food types, but not significantly different between in OHF and young groups. CONCLUSIONS: Our findings suggest that eating textured foods will lead to increased masticatory load and therefore increased muscle activity, especially in older adults. Application of textured food may change dietary habits in older adults.

Spatiotemporal regulation of PCNA ubiquitination in damage tolerance pathways.

DNA is constantly exposed to a wide variety of exogenous and endogenous agents, and most DNA lesions inhibit DNA synthesis. To cope with such problems during replication, cells have molecular mechanisms to resume DNA synthesis in the presence of DNA lesions, which are known as DNA damage tolerance (DDT) pathways. The concept of ubiquitination-mediated regulation of DDT pathways in eukaryotes was established via genetic studies in the yeast Saccharomyces cerevisiae, in which two branches of the DDT pathway are regulated via ubiquitination of proliferating cell nuclear antigen (PCNA): translesion DNA synthesis (TLS) and homology-dependent repair (HDR), which are stimulated by mono- and polyubiquitination of PCNA, respectively. Over the subsequent nearly two decades, significant progress has been made in understanding the mechanisms that regulate DDT pathways in other eukaryotes. Importantly, TLS is intrinsically error-prone because of the miscoding nature of most damaged nucleotides and inaccurate replication of undamaged templates by TLS polymerases (pols), whereas HDR is theoretically error-free because the DNA synthesis is thought to be predominantly performed by pol δ, an accurate replicative DNA pol, using the undamaged sister chromatid as its template. Thus, the regulation of the choice between the TLS and HDR pathways is critical to determine the appropriate biological outcomes caused by DNA damage. In this review, we summarize our current understanding of the species-specific regulatory mechanisms of PCNA ubiquitination and how cells choose between TLS and HDR. We then provide a hypothetical model for the spatiotemporal regulation of DDT pathways in human cells.

Stepwise multipolyubiquitination of p53 by the E6AP-E6 ubiquitin ligase complex.

The human papillomavirus (HPV) oncoprotein E6 specifically binds to E6AP (E6-associated protein), a HECT (homologous to the E6AP C terminus)-type ubiquitin ligase, and directs its ligase activity toward the tumor suppressor p53. To examine the biochemical reaction in vitro, we established an efficient reconstitution system for the polyubiquitination of p53 by the E6AP-E6 complex. We demonstrate that E6AP-E6 formed a stable ternary complex with p53, which underwent extensive polyubiquitination when the isolated ternary complex was incubated with E1, E2, and ubiquitin. Mass spectrometry and biochemical analysis of the reaction products identified lysine residues as p53 ubiquitination sites. A p53 mutant with arginine substitutions of its 18 lysine residues was not ubiquitinated. Analysis of additional p53 mutants retaining only one or two intact ubiquitination sites revealed that chain elongation at each of these sites was limited to 5-6-mers. We also determined the size distribution of ubiquitin chains released by en bloc cleavage from polyubiquitinated p53 to be 2-6-mers. Taken together, these results strongly suggest that p53 is multipolyubiquitinated with short chains by E6AP-E6. In addition, analysis of growing chains provided strong evidence for step-by-step chain elongation. Thus, we hypothesize that p53 is polyubiquitinated in a stepwise manner through the back-and-forth movement of the C-lobe, and the permissive distance for the movement of the C-lobe restricts the length of the chains in the E6AP-E6-p53 ternary complex. Finally, we show that multipolyubiquitination at different sites provides a signal for proteasomal degradation.

Effect of tablets containing lactoferrin and lactoperoxidase on gingival health in adults: A randomized, double-blind, placebo-controlled clinical trial.

OBJECTIVE: To evaluate the effect of tablets containing lactoferrin (LF) and lactoperoxidase (LPO) on gingival health and oral health-related quality of life in healthy adults. BACKGROUND: Lactoferrin and LPO are host defense factors found in saliva that may contribute to oral health. MATERIALS AND METHODS: One hundred and fifty adults were randomly assigned to the administration of high-dose tablets (LF 60 mg/d, LPO 7.8 mg/d), low-dose tablets (LF 20 mg/d, LPO 2.6 mg/d), or placebo tablets for 12 weeks. The gingival index (GI) and plaque index (PlI) were measured at baseline and after 12 weeks. Oral health-related quality of life was assessed by the Oral Health Impact Profile (OHIP) at baseline and at 4, 8, and 12 weeks. RESULTS: One hundred and nine healthy subjects were included in the efficacy analysis. In the high-dose group, the GI was significantly reduced after 12 weeks of treatment, and the reduction in GI in the high-dose group was significant compared with the placebo group. In both the high-dose group and the low-dose group, PlI showed a significant decrease at 12 weeks compared with baseline. The total OHIP score was significantly reduced at 12 weeks in the high-dose group. In addition, the OHIP functional limitation subscale displayed significant improvement in the high-dose groups compared with the placebo group at 12 weeks. No adverse reactions or serious adverse events related to the test tablets were observed in any of participants during the study, and the incidence of adverse events unrelated to the tablets did not differ significantly among the groups. CONCLUSION: These results suggest that intake of tablets containing LF (60 mg/d) and LPO (7.8 mg/d) can potentially improve gingival inflammation and oral health-related quality of life in healthy adults.

Improvement of salivary flow and oral wetness by a lip trainer device and sonic toothbrush in older Japanese men and women with dry mouth.

Dry mouth, caused by decreased salivary gland function and/or weak salivary stimulation, can severely affect oral health in older individuals. Therefore, the aim of this study is to evaluate whether a lip trainer device and sonic toothbrush can improve salivary flow and oral wetness in older patients complaining of dry mouth. Overall, 39 subjects aged ≥60 years who had at least 20 natural teeth were randomly assigned to use a lip trainer device (group P, n = 13) or a sonic toothbrush (group S, n = 13). The subjects who did not experience oral dryness were included as controls (group C; n = 13). The unstimulated and stimulated salivary flow rates and oral wetness were measured at baseline, 1 and 6 months. The unstimulated salivary flow significantly increased in both groups at 1 and 6 months (P < 0.05). The stimulated salivary flow was also significantly increased in group P (P < 0.01) compared with the level at baseline. However, no significant difference was observed over time in group S. Oral wetness of the tongue and buccal mucosa in group P had significantly improved at 1 and 6 months (P < 0.05). Dry mouth in older individuals may be improved by using a lip trainer device or a sonic toothbrush.

Ability to control directional lip-closing force during voluntary lip pursing in healthy young adults.

BACKGROUND: It is considered important to evaluate the ability to control lip-closing force (LCF). OBJECTIVE: This study aimed to investigate the ability to control directional LCF. METHODS: The experimental system included an apparatus developed to measure LCF during lip pursing in eight directions (upper, lower, right, left and the four directions in between) and a display showing the exerted LCF and a target value in each direction in real time. Twenty subjects (10 men and 10 women) were instructed to maintain the LCF at a specific target value using visual feedback. Based on our preliminary experiments, the target value was set as 50% of the maximum LCF, and the range was set at the target value ±8%. The accuracy rate was defined as the ratio of the matched time, in which the subject was able to keep the LCF in the target range, to the total 3 seconds. RESULTS: The accuracy rate of men was higher than in women in the lower, lower left and lower right directions. The accuracy rate of the directional LCF differed significantly depending on the direction. In assessing the accuracy rate for each directional LCF, the rates of upper and lower directional LCF were significantly higher than those of oblique directional LCF. No significant relationship was observed between the accuracy rate and the maximum LCF except for one direction in men subjects. CONCLUSIONS: Our findings suggest that the ability to control directional LCF is affected by sex and the force direction.

Preferential digestion of PCNA-ubiquitin and p53-ubiquitin linkages by USP7 to remove polyubiquitin chains from substrates.

Ubiquitin-specific protease 7 (USP7) regulates various cellular pathways through its deubiquitination activity. Despite the identification of a growing number of substrates of USP7, the molecular mechanism by which USP7 removes ubiquitin chains from polyubiquitinated substrates remains unexplored. The present study investigated the mechanism underlying the deubiquitination of Lys63-linked polyubiquitinated proliferating cell nuclear antigen (PCNA). Biochemical analyses demonstrated that USP7 efficiently removes polyubiquitin chains from polyubiquitinated PCNA by preferential cleavage of the PCNA-ubiquitin linkage. This property was largely attributed to the poor activity toward Lys63-linked ubiquitin chains. The preferential cleavage of substrate-ubiquitin linkages was also observed for Lys48-linked polyubiquitinated p53 because of the inefficient cleavage of the Lys48-linked ubiquitin chains. The present findings suggest a mechanism underlying the removal of polyubiquitin signals by USP7.

Experimentally induced rhythmic jaw muscle activities during non-rapid eye movement sleep in freely moving guinea pigs.

Rhythmic jaw muscle activities frequently occur during non-rapid eye movement sleep in patients with sleep bruxism. The present study aimed to investigate the response characteristics of the masticatory rhythm generation during non-rapid eye movement sleep in animals. Eleven guinea pigs were surgically prepared for polygraphic recordings by electromyography, electrooculography, electroencephalography and electrocardiography with the implantation of a stimulating electrode. Repetitive electrical microstimulations at three intensities were applied to the corticobulbar tract under freely moving conditions. The rhythmic electro-myographic responses of the digastric and masseter muscles were scored and analysed. Changes in cortical electro-encephalographic power and heart rate in association with these stimulations were quantified. Microstimulations to the corticobulbar tract induced rhythmic jaw muscle activities in digastric muscles, occasionally with masseter activities during wakefulness and non-rapid eye movement sleep. The response rate of rhythmic jaw muscle activities was significantly lower (p < 0.01) and the response latency was significantly longer (p < 0.01) during non-rapid eye movement sleep than during wakefulness. At higher stimulus intensities, the response rate increased and response latency decreased. The mean burst intervals of the digastric and masseter muscles were similar regardless of vigilance states and stimulus intensities. Induced rhythmic jaw muscle activities during non-rapid eye movement sleep were followed by a transient decrease in delta power and increases in beta power and heart rate. During non-rapid eye movement sleep, the masticatory motor system is able to generate rhythmic outputs to the jaw muscles in response to facilitatory inputs although the responsiveness was decreased from wakefulness.

Activation of TRPV1 and TRPM8 Channels in the Larynx and Associated Laryngopharyngeal Regions Facilitates the Swallowing Reflex.

The larynx and associated laryngopharyngeal regions are innervated by the superior laryngeal nerve (SLN) and are highly reflexogenic. Transient receptor potential (TRP) channels have recently been detected in SLN innervated regions; however, their involvement in the swallowing reflex has not been fully elucidated. Here, we explore the contribution of two TRP channels, TRPV1 and TRPM8, located in SLN-innervated regions to the swallowing reflex. Immunohistochemistry identified TRPV1 and TRPM8 on cell bodies of SLN afferents located in the nodose-petrosal-jugular ganglionic complex. The majority of TRPV1 and TRPM8 immunoreactivity was located on unmyelinated neurons. Topical application of different concentrations of TRPV1 and TRPM8 agonists modulated SLN activity. Application of the agonists evoked a significantly greater number of swallowing reflexes compared with the number evoked by distilled water. The interval between the reflexes evoked by the agonists was shorter than that produced by distilled water. Prior topical application of respective TRPV1 or TRPM8 antagonists significantly reduced the number of agonist-evoked reflexes. The findings suggest that the activation of TRPV1 and TRPM8 channels present in the swallowing-related regions can facilitate the evoking of swallowing reflex. Targeting the TRP channels could be a potential therapeutic strategy for the management of dysphagia.

Regulation of HLTF-mediated PCNA polyubiquitination by RFC and PCNA monoubiquitination levels determines choice of damage tolerance pathway.

DNA-damage tolerance protects cells via at least two sub-pathways regulated by proliferating cell nuclear antigen (PCNA) ubiquitination in eukaryotes: translesion DNA synthesis (TLS) and template switching (TS), which are stimulated by mono- and polyubiquitination, respectively. However, how cells choose between the two pathways remains unclear. The regulation of ubiquitin ligases catalyzing polyubiquitination, such as helicase-like transcription factor (HLTF), could play a role in the choice of pathway. Here, we demonstrate that the ligase activity of HLTF is stimulated by double-stranded DNA via HIRAN domain-dependent recruitment to stalled primer ends. Replication factor C (RFC) and PCNA located at primer ends, however, suppress en bloc polyubiquitination in the complex, redirecting toward sequential chain elongation. When PCNA in the complex is monoubiquitinated by RAD6-RAD18, the resulting ubiquitin moiety is immediately polyubiquitinated by coexisting HLTF, indicating a coupling reaction between mono- and polyubiquitination. By contrast, when PCNA was monoubiquitinated in the absence of HLTF, it was not polyubiquitinated by subsequently recruited HLTF unless all three-subunits of PCNA were monoubiquitinated, indicating that the uncoupling reaction specifically occurs on three-subunit-monoubiquitinated PCNA. We discuss the physiological relevance of the different modes of the polyubiquitination to the choice of cells between TLS and TS under different conditions.