The effect of masseter muscle mass on the rate of experimental tooth movement in rats

BACKGROUND

Previous clinical observational studies have suggested that orthodontic tooth movement (OTM) is related, at least partly, to the mass and/or capabilities of the masticatory muscles.

OBJECTIVES

Our study aimed to examine the influence of masticatory muscle mass on the OTM in an animal experimental model in which the masseter muscle was modulated by botulinum neurotoxin type A (BTX) injection.

METHODS

Eighteen Wistar rats were equally divided into two groups: BTX injection and control. BTX was injected bilaterally into the masseter muscles. Three days after the injection, the maxillary left first molars were orthodontically moved for 14 days. At the end of the experiment, micro-computed tomography was performed to evaluate the rate of OTM and bone morphometry. The masseter muscles were weighed and prepared for histological analyses.

RESULTS

The masseter muscle mass in the BTX group was less than that in the control group, and histological findings showed atrophy of muscle fibers. The rate of OTM was significantly higher in the BTX group than in the control group. Furthermore, a negative correlation was detected between masseter muscle mass and OTM in the BTX group. Bone morphometry showed no difference between the control and BTX groups.

CONCLUSION

Decreased masseter muscle mass was found to be closely related to an increase in the rate of OTM in rats using BTX injection to modify the masseter muscle mass. Masseter muscle mass could be a predictive factor for OTM in rats injected with BTX.

Preparation and Readout of Multielectron High-Spin States in a Gate-Defined GaAs/AlGaAs Quantum Dot

We report the preparation and readout of multielectron high-spin states, a three-electron quartet, and a four-electron quintet, in a gate-defined GaAs/AlGaAs single quantum dot using spin filtering by quantum Hall edge states coupled to the dot. The readout scheme consists of mapping from multielectron to two-electron spin states and a subsequent two-electron spin readout, thus obviating the need to resolve dense multielectron energy levels. Using this technique, we measure the relaxations of the high-spin states and find them to be an order of magnitude faster than those of low-spin states. Numerical calculations of spin relaxation rates using the exact diagonalization method agree with the experiment. The technique developed here offers a new tool for the study and application of high-spin states in quantum dots.

Effects of Oral Management on Elderly Patients with Pneumonia

OBJECTIVES

In this study, we examined the factors influencing the presence or absence of dental intervention in patients with pneumonia in an acute-care hospital, focusing on oral intake and its status.

DESIGN

Observational study.

SETTING

Teikyo University School of Medicine, Mizonokuchi Hospital.

PARTICIPANTS

Patients ≥65 years of age who were admitted to the Teikyo University School of Medicine, Mizonokuchi Hospital between January 1, 2018 and December 31, 2019 with pneumonia who were referred to the Department of Rehabilitation with suspected dysphagia were included in the study. Fifty patients who underwent dental intervention were compared with 50 controls who had received no dental interventions prior to the opening of the dental department.

MEASUREMENTS

Time series matching was retrospectively performed using the Oral Health Assessment Tool (OHAT). From the medical records, age at admission, sex, pneumonia severity classification (age, dehydration, respiratory failure, orientation disturbance, and blood pressure [A-DROP] score), body mass index, Charlson's Comorbidity Index, OHAT, functional oral intake scale (FOIS) score at admission and discharge, and the length of hospital stay were retrieved; FOIS level ≥4 was defined as established oral intake.

RESULTS

The number of patients in the control group before matching was 179. Twelve patients with missing information and seven patients who died in the hospital were excluded from this study. Multivariable logistic regression analysis showed that dental intervention (odds ratio 3.0, p = 0.014) was associated with the establishment of oral intake at discharge. Multiple logistic regression analysis showed that dental intervention was a significant factor for FOIS at discharge (p = 0.002) and the length of hospital stay (p = 0.039).

CONCLUSION

Oral management with dental intervention was associated with establishing oral intake and reducing hospital stay in patients with pneumonia, regardless of pneumonia severity or comorbidities.

The relationship between jaw-opening force and the cross-sectional area of the suprahyoid muscles in healthy elderly

We conducted a clinical cross-sectional study to examine the relationship between jaw-opening force and the cross-sectional area of the suprahyoid muscles and whole skeletal muscle mass. Subjects were healthy 39 males and 51 females without dysphagia and sarcopenia, aged 65 years and older. Jaw-opening force was measured three times using a jaw-opening sthenometer; the maximum of these three was taken as the measurement value. The cross-sectional area of the geniohyoid and anterior belly of the digastric muscles were evaluated using ultrasonography. The skeletal muscle mass index, gait speed and grip strength were evaluated according to the diagnostic criteria of the Asian Working Group for Sarcopenia. For each sex, a multiple regression analysis determined the factors that affect jaw-opening force. Jaw-opening force was associated with the cross-sectional area of the geniohyoid muscle in males (regression coefficient [β] = 0.441, 95% confidence interval [CI] = 14.28-56.09) and females (β = 0.28, 95% CI = 3.10-54.57). Furthermore, in females only, jaw-opening force was associated with the skeletal muscle mass index (β = 0.40, 95% CI = 3.67-17.81). In contrast, jaw-opening force was not associated with the cross-sectional area of the anterior belly of the digastric muscle in either sex. In healthy elderly males and females, jaw-opening force was positively associated with the cross-sectional area of the geniohyoid muscle. However, the jaw-opening force was positively associated with the skeletal muscle mass index only in females.

Mechanism of motor coordination of masseter and temporalis muscles for increased masticatory efficiency in mice

The demand for the use of mice as animal models for elucidating the pathophysiologies and pathogeneses of oral motor disorders has been increasing in recent years, as more and more kinds of genetically modified mice that express functional disorders of the stomatognathic system become available. However, the fundamental characteristics of mouse jaw movements during mastication have yet to be fully elucidated. The purpose of this study was to investigate the roles of the masseter and temporalis muscles, and the mechanisms of motor coordination of these muscles for increasing masticatory efficiency in the closing phase in mice. Twenty-two male Jcl:ICR mice were divided into control (n = 8), masseter-hypofunction (n = 7) and temporalis-hypofunction groups (n = 7). Botulinum neurotoxin type A (BoNT⁄A) was used to induce muscle hypofunction. The masticatory movement path in the horizontal direction during the occlusal phase became unstable after BoNT⁄A injection into the masseter muscle. BoNT⁄A injection into the temporalis muscle decreased antero-posterior excursion of the late-closing phase corresponding to the power phase of the chewing cycle. These results suggest that the masseter plays an important role in stabilizing the grinding path, where the food bolus is ground by sliding the posterior teeth from back to front during the occlusal phase. The temporalis plays a major role in retracting the mandible more posteriorly in the early phase of closing, extending the grinding path. Masticatory efficiency is thus increased based on the coordination of activities by the masseter and temporalis muscles.

Allele-specific genome editing and correction of disease-associated phenotypes in rats using the CRISPR-Cas platform

The bacterial CRISPR/Cas system has proven to be an efficient gene-targeting tool in various organisms. Here we employ CRISPR/Cas for accurate and efficient genome editing in rats. The synthetic chimeric guide RNAs (gRNAs) discriminate a single-nucleotide polymorphism (SNP) difference in rat embryonic fibroblasts, allowing allele-specific genome editing of the dominant phenotype in (F344 × DA)F1 hybrid embryos. Interestingly, the targeted allele, initially assessed by the allele-specific gRNA, is repaired by an interallelic gene conversion between homologous chromosomes. Using single-stranded oligodeoxynucleotides, we recover three recessive phenotypes: the albino phenotype by SNP exchange; the non-agouti phenotype by integration of a 19-bp DNA fragment; and the hooded phenotype by eliminating a 7,098-bp insertional DNA fragment, evolutionary-derived from an endogenous retrovirus. Successful in vivo application of the CRISPR/Cas system confirms its importance as a genetic engineering tool for creating animal models of human diseases and its potential use in gene therapy.

Dissolution of molybdenum-silicon (-boron) alloys using a mixture of sulfuric, nitric and hydrofluoric acids and a sequential correction method for ICP-AES analysis

For the major component analysis of Mo-Si (-B) alloys by ICP-AES, an appropriate dissolution method is necessary. The general procedure using a HNO3-HF mixture cannot be applied for Mo-Si (-B) alloys due to Si volatilization followed by violent reaction and due to MoO2 precipitation in the preparation of a Mo standard solution from metallic Mo. Good results were obtained with a mixture of 10 mL H2SO4, 1 mL HNO3, 2 mL HF and 12 mL H2O for Mo-Si (-B) alloys. The samples were completely dissolved at room temperature without any losses. A sequential correction method is also suggested to correct several errors in ICP-AES analysis such as fluctuation in the emission intensities, spectral interferences, non-spectral interferences and blank values.

Learning induces a CDC2-related protein kinase, KKIAMRE

To elucidate molecular mechanisms in learning and memory, we analyzed expression of mRNAs in brains of rabbits undergoing eyeblink conditioning. Infusion of the transcription inhibitor actinomycin D into the cerebellar interpositus nucleus reversibly blocked learning but not performance of the conditioned response. Differential display PCR analysis of cerebellar interpositus RNAs from trained and pseudotrained rabbits identified a 207 bp band that was induced with learning. The fragment was used to isolate a cDNA from a lambdagt11 rabbit brain library containing a 1698 bp open reading frame. The deduced amino acid sequence contains the KKIAMRE motif, which is conserved among cell division cycle 2 (cdc2)-related kinases. These results suggest that there is a new category of cdc2-related kinases in the brain whose function may be important in learning and memory.

Co-injection of beta-amyloid with ibotenic acid induces synergistic loss of rat hippocampal neurons

Senile plaques are a pathological hallmark of Alzheimer's disease. The major component of senile plaques is beta-amyloid which consists of approximately 4000 mol. wt of peptide. Accumulating evidence suggests that beta-amyloid may represent the underlying cause of Alzheimer's disease. In vitro, beta-amyloid has been shown either to be directly neurotoxic or to potentiate neurotoxic effects of excitatory amino acids. However, beta-amyloid toxicity in vivo has not always been reproducible. In this study, we injected beta-amyloid fragment 1-40 or 25-35 alone or in combination with a small amount of ibotenic acid, an excitatory amino acid, into rat hippocampus, and examined the histological and immunohistochemical changes two weeks after injection. Although beta-amyloid alone or ibotenic acid alone exerted only minimal degenerating effects on neurons just around the injection site, the co-injection of beta-amyloid 1-40 or beta-amyloid 25-35 with ibotenic acid produced drastic neuronal loss; the haematoxylin-eosin staining revealed that most neurons not only around the injection site but also in distant areas including CA1, CA4 and dentate gyrus were depleted. The neuronal loss occurred in a dose-dependent manner with respect to ibotenic acid. Immunohistochemical analysis showed that beta-amyloid with ibotenic acid induced great depletion of microtubule-associated protein-2 immunoreactivity and infiltration of astrocytes and microglia on neuronal loss. In addition, some apoptotic neuronal death indicated by DNA fragmentation and nucleic condensation was observed. Beta-amyloid depositions detected by two different types of anti-human beta-amyloid antibodies were limited to the injection site. Dizocilpine maleate (MK-801), an antagonist for an excitatory amino acid receptor, completely inhibited the neuronal death in rat hippocampus. These results suggest that the co-injection of beta-amyloid with a small amount of ibotenic acid provides a useful model for investigation of the pathogenetic mechanisms leading to Alzheimer's disease.

A supplemental measure of stay-times in the light box on step-through passive avoidance

The avoidance behavior of rats in a typical step-through passive avoidance task was evaluated by using two types of time measurements that differed from traditional step-through latency (STL). The total stay-time in the light box (TL) was calculated as an index of the dark box avoidance throughout the retention trial, counting the time before and after the first step-through. The total stay-time in the far area of the light box (TF) was calculated as an index of the tendency to keep away from the dark box. TL, TF and the STL increased with electrical shock intensity at acquisition trials and gradually decreased through an extinction procedure. The discrepancy between our new measures and the STL was observed when the effects of a new drug, RS-8359, which was reported to ameliorate ischemic brain damage, were examined in ischemic animals. TL, TF and STL decreased in rats receiving brain ischemia, and we found that after treatment with RS-8359, TL and TF increased, but no effect was observed on STL. The discrepancy observed suggests that a short STL does not necessarily imply a loss of avoidance behaviour. Passive avoidance tests can be more revealing about a drug's effects when stay-time measures are used.

Ischaemia-induced change in clathrin preceding delayed neuronal death

The mechanism underlying the change in clathrin immunohistochemistry preceding delayed neuronal death (DND) was studied in gerbils. The ischaemic change observed with chc5.9 anti-clathrin antibody in hippocampal CA1 was initially ameliorated by pentobarbital, which blocks DND, but 1 day after ischaemia, no change in the immunoreactivity of the SDS-denatured clathrin molecule was detected by Western blotting and no change in the clathrin content in CA1 was detected by SDS-PAGE. No ischaemia-induced change in immunohistochemistry was observed with another monoclonal anti-clathrin antibody, X-22. The above results imply that some modifications that affect the structure of clathrin molecules around the chc5.9 specific epitope may be a crucial step in the course of DND.

Involvement of clathrin light chains in the pathology of Pick's disease; implication for impairment of axonal transport

Clathrin, which constitutes coated vesicles and plays important roles in neuronal functions, has been reported to be involved in the pathology of Alzheimer's disease. In the brains of the patients with Pick's disease, distribution of clathrin was immunohistochemically investigated using monoclonal antibodies binding to different epitopes of clathrin light chain a and b. All the antibodies intensely labeled Pick's body and some perikarya of neurons, indicating impairment of slow axonal transport b (SCb). Antibodies against neurofilament, kinesin and synaptophysin also labeled Pick's body. These observations suggested impairment of axonal transport in the brains with Pick's disease, and might contribute to elucidating the pathology of Pick's body forming. It is implied that common pathological processes might lie in Alzheimer's disease and Pick's disease.

"Myocardial stunning"-like phenomenon during a crisis of pheochromocytoma

A woman with a pheochromocytoma crisis initiated by cardiogenic shock showed severely impaired left ventricular contraction at the time of admission. Heart failure was improved rapidly, and an endomyocardial biopsy performed on the 11th day of admission showed findings compatible with "catecholamine cardiomyopathy". Regarding the pathogenesis of short-duration left ventricular dysfunction, catecholamine-induced cardiotoxicity would probably be the initial consideration. However, in this case, after considering the electrocardiogram on admission and a series of left ventriculograms, "myocardial stunning" following diffuse coronary vasospasm induced by catecholamine crisis may have also contributed to the dysfunction.

Involvement of clathrin light chains in the pathology of Alzheimer's disease

Clathrin, which constitutes coated vesicles, plays important roles in neuronal functions. In the brains of the patients with Alzheimer's disease, distribution of clathrin was immunohistochemically investigated using four monoclonal antibodies against clathrin light chains, LCB.1, LCB.2, X-16 and CON.1, to study the involvement of clathrin in the pathology of Alzheimer's disease. LCB.1, LCB.2, X-16, and CON.1 bind to the aminoterminus of the clathrin light chain b(LCb), to the neuron-specific insert of LCb, to the light chain a(LCa), and to LCa and LCb, respectively. In Alzheimer brains, granular staining of LCB.2 around neurons in the hippocampus was weaker or patchily defected in comparison with control brains. Some neurofibrillary tangles and neurons were intensely stained in Alzheimer brains by LCB.2, whereas neurons were weakly stained in control brains. Crowns of some senile plaques in the brains of early onset Alzheimer's disease were positively stained by LCB.2. LCB.1 supported the observations of LCB.2. Reactive astrocytes in Alzheimer brains were intensely stained by X-16. On the other hand, Western blot analysis using LCB.2 and X-16 demonstrated no apparent differences in protein amounts and molecular weights of LCa and LCb between control and Alzheimer brains. These observations demonstrated abnormal distribution of clathrin in Alzheimer brains, implying impairment of axonal transport in this disease.

An immunohistochemical study of MAP2 and clathrin in gerbil hippocampus after cerebral ischemia

Changes in MAP2 and clathrin immunoreactivity were studied in gerbil hippocampus after transient cerebral ischemia. MAP2 immunoreactivity decreased significantly by 1 h in the subiculum-CA1 and CA2 areas which correspond to reactive change, while no decrease was observed in CA1 until day 4. Before the initiation of delayed neuronal death, MAP2 immunoreactivity was not changed in CA1. On the other hand clathrin immunoreactivity increased in the pyramidal cell layer of CA1 by 3 h after ischemia and remained high for 2 days. Clathrin immunoreactivity in the pyramidal cell layer of CA1 diminished after delayed neuronal death. The transient change of clathrin was noted especially in CA1 in the period prior to delayed neuronal death. These results imply an abnormal change in clathrin turnover after ischemia, which may participate in the pathogenesis of delayed neuronal death.

[Early hearing screening for brain impairment baby--Crib-O-Gram]

A retrospective investigation by ABR and COG was performed to children with brain impairment determined by neurological follow-up out of children who had hearing screening test, and the relationship with the presence or not of hearing loss was analyzed. The results obtained are as follows. 1) The failure rate in COG test was 46.3% in the brain impairment group. It was significantly higher than in the hearing loss high-risk group and the low-risk group. However, 20% of 101 children with brain impairment ware cases in which the COG test could not be performed. Presumably , this is due to the special character of COG test. 2) In the brain impairment children group, the rate of true positive, true negative and false negative by COG as to the presence or not of hearing loss stood at 68.8%, 31.3%, and 0% respectively. Since, however, 32.4% of the children who failed to pass COG had hearing loss, the usefulness of COG can be said to be high. 3) The incidence of hearing loss was significantly high at 15.0% in the brain impairment group compared with other groups. In contrast, the rate of true positive was significantly high, the rate of true negative significantly low and no false negative was noted in the low-risk group. So COG was considered appropriate as a hearing screening device that can be used from the neonatal period. 4) In the brain impairment group, the rate of true positive by ABR was high at 86.7%, but the rate of true negative was 13%.(ABSTRACT TRUNCATED AT 250 WORDS)