Effects of potato resistant starch intake on insulin sensitivity, related metabolic markers and appetite ratings in men and women at risk for type 2 diabetes: a pilot cross-over randomised controlled trial.

BACKGROUND: The intake of certain types of resistant starch (RS) has been associated in some studies with increased whole-body insulin sensitivity. This randomised, cross-over pilot trial evaluated the effect of consuming cooked, then chilled potatoes, a source of RS, compared to isoenergetic, carbohydrate (CHO)-containing control foods, on insulin sensitivity and related markers. METHODS: Nineteen adults with body mass index 27.0-39.9 kg m-2 consumed 300 g day-1 RS-enriched potatoes (approximately two potatoes; ~18 g RS) or CHO-based control foods, as part of lunch, evening and snack meals, over a 24-h period. After an overnight fast, insulin sensitivity, CHO metabolism markers, free fatty acids, breath hydrogen levels and appetite were assessed for up to 5 h after the intake of a standard breakfast. The primary endpoint was insulin sensitivity, assessed with the Matsuda index. P < 0.05 (one-sided) was considered statistically significant. RESULTS: Insulin sensitivity was not significantly different between the potato and control conditions. The potato intervention resulted in higher postprandial breath hydrogen (P = 0.037), lower postprandial free fatty acid concentrations (P = 0.039) and lower fasting plasma glucose (P = 0.043) compared to the control condition. Fullness ratings were significantly lower after potato versus control (P = 0.002). No other significant effects were observed; however, there was a trend toward lower fasting insulin (P = 0.077) in the potato versus the control condition. CONCLUSIONS: The results of this pilot study suggest RS-enriched potatoes may have a favourable impact on carbohydrate metabolism and support the view that additional research in a larger study sample is warranted.

Influence of rotational speed on torque/force generation and shaping ability during root canal instrumentation of extracted teeth with continuous rotation and optimum torque reverse motion.

AIM: To evaluate how different rotational speeds affect the torque/force generation and shaping ability of rotary root canal instrumentation using JIZAI (MANI, Utsunomiya, Japan) nickel-titanium instruments in continuous rotation and optimum torque reverse (OTR) motion. METHODOLOGY: Mesial root canals of extracted mandibular molars were instrumented up to size 25, 0.04 taper using JIZAI instruments, and anatomically matched canals were selected based on geometric features of the canal [canal volume (mm3 ), surface area (mm2 ), length, 15°-20° curvature and radius of curvature (4-8 mm)] after micro-computed tomographic scanning. An automated root canal instrumentation and torque/force analysing device was programmed to permit a simulated pecking motion (2 s downward and 1 s upward at 50 mm min-1 ). The selected canals were prepared with size 25, 0.06 taper JIZAI instruments using continuous rotation or OTR motion and further subdivided according to the rotational speed (300 or 500 rpm, n = 10 each). Real-time clockwise/counterclockwise torque and downward/upward force were recorded using a custom-made torque/force analysing device. Then, the registered pre- and post-operative micro-computed tomographic datasets were examined to evaluate the canal volume changes and centring ratios at 1, 3, 5 and 7 mm from the apical foramen. Data were analysed using two-way analysis of variance or the Kruskal-Wallis test and Mann-Whitney U test with Bonferroni correction (α = 5%). RESULTS: Maximum upward force and clockwise torque were significantly smaller in 500 rpm groups than in 300 rpm groups (P < .05); however, no significant difference was found between continuous rotation and OTR motion (P > .05). OTR motion developed higher maximum counterclockwise torque than continuous rotation (P < .05). Maximum downward force, canal volume changes and centring ratios were not significantly different among all groups (P > .05). There was no file fracture in any of the groups. CONCLUSIONS: Under laboratory conditions using JIZAI instruments, a rotational speed of 500 rpm generated significantly lower maximum screw-in forces and torque values than rotational speed of 300 rpm. Continuous rotation and OTR motion performed similarly in shaping the canals.

8-Nitro-cGMP is a promoter of osteoclast differentiation induced by RANKL.

Osteoclasts are multinucleated giant cells differentiated from monocyte-macrophage-lineage cells under stimulation of receptor activator of nuclear factor κ-B (RANK) ligand (RANKL) produced by osteoblasts and osteocytes. Although it has been reported that nitric oxide (NO) and reactive oxygen species (ROS) are involved in this process, the mechanism by which these labile molecules promote osteoclast differentiation are not fully understood. In this study, we investigated the formation and function of 8-nitro-cGMP, a downstream molecule of NO and ROS, in the process of osteoclast differentiation in vitro. 8-Nitro-cGMP was detected in mouse bone marrow macrophages and osteoclasts differentiated from macrophages in the presence of RANKL. Inhibition of NO synthase suppressed the formation of 8-nitro-cGMP as well as RANKL-induced osteoclast differentiation from macrophages. On the other hand, RANKL-induced osteoclast differentiation was promoted by addition of 8-nitro-cGMP to the cultures. In addition, 8-nitro-cGMP enhanced the mRNA expression of RANK, the receptor for RANKL. However, 8-bromo-cGMP, a membrane-permeable derivative of cGMP, did not have an effect on either RANKL-induced osteoclast differentiation or expression of the RANK gene. These results suggest that 8-nitro-cGMP is a novel positive regulator of osteoclast differentiation, which might help to explain the roles of NO and ROS in osteoclast differentiation.

Differences in the developmental origins of the periosteum may influence bone healing.

BACKGROUND AND OBJECTIVE: The jaw bone, unlike most other bones, is derived from neural crest stem cells, so we hypothesized that it may have different characteristics to bones from other parts of the body, especially in the nature of its periosteum. The periosteum exhibits osteogenic potential and has received considerable attention as a grafting material for the repair of bone and joint defects. MATERIAL AND METHODS: Gene expression profiles of jaw bone and periosteum were evaluated by DNA microarray and real-time polymerase chain reaction. Furthermore, we perforated an area 2 mm in diameter on mouse frontal and parietal bones. Bone regeneration of these calvarial defects was evaluated using microcomputed tomography and histological analysis. RESULTS: The DNA microarray data revealed close homology between the gene expression profiles within the ilium and femur. The gene expression of Wnt-1, SOX10, nestin, and musashi-1 were significantly higher in the jaw bone than in other locations. Microcomputed tomography and histological analysis revealed that the jaw bone had superior bone regenerative abilities than other bones. CONCLUSION: Jaw bone periosteum exhibits a unique gene expression profile that is associated with neural crest cells and has a positive influence on bone regeneration when used as a graft material to repair bone defects. A full investigation of the biological and mechanical properties of jaw bone as an alternative graft material for jaw reconstructive surgery is recommended.

Genome-wide association study of degenerative bony changes of the temporomandibular joint.

OBJECTIVES: To identify susceptibility genes underlying degenerative bony changes of the temporomandibular joint (TMJ). MATERIALS AND METHODS: Bony changes of the TMJ condylar head were diagnosed by examination of panoramic radiographs and/or magnetic resonance images and/or computed tomography images. We conducted a genome-wide association study (GWAS) of 146 cases with TMJ degeneration and 374 controls from East Asian populations using an Illumina HumanOmniExpress BeadChip. After rigorous quality-control filtering, approximately 550,000 single nucleotide polymorphisms (SNPs) were used for tests of associations with disease status. RESULTS: Forty-one SNPs at 22 independent loci showed association signals at P < 1 × 10(-4). The SNP rs878962, which maps on an intron of TSPAN9 on chromosome 12, showed the strongest association (combined OR = 1.89, 95% confidence interval = 1.43-2.50, P = 8.1 × 10(-6)). According to in silico predictions of the 41 SNPs, two intronic SNPs of APOL3 (rs80575) and MRC2 (rs2460300) may fall within regulatory elements and affect DNA-protein interactions. We could not replicate SNPs located on genes that have been reported to be associated with temporomandibular disorder or temporomandibular osteoarthritis in previous studies at P < 1 × 10(-4). CONCLUSIONS: Our GWAS identified 22 independent loci showing suggestive association signals with degenerative bony changes of the TMJ. These loci provide good candidates for future follow-up studies.

Three-dimensional evaluation of upper airway in patients with different anteroposterior skeletal patterns.

OBJECTIVES: To investigate variability in the upper airway of subjects with different anteroposterior skeletal patterns by evaluating the volume and the most constricted cross-sectional area of the pharyngeal airway and defining correlations between the different variables. MATERIAL AND METHODS: The study sample consisted of 60 patients (29 boys, 31 girls) divided into three groups: Class I (1 ≤ ANB ≤ 3), Class II (ANB>3), and Class III (ANB<1), to evaluate how the jaw relationship affects the airway volume and the most constricted cross-sectional area (Min-CSA). Differences between groups were determined using the Tukey-Kramer test. Correlations between variables were tested using Pearson's correlation coefficient. RESULTS: The volume and the Min-CSA of the pharyngeal airway (PA) were significantly related to anteroposterior skeletal patterns (p < 0.05). The nasopharyngeal airway (NA) volume of Class I and Class III subjects was significantly larger than that of Class II subjects (p < 0.05). The Min-CSA and the length of PA were significantly related to the volume of PA (p < 0.05). The site and the size of the Min-CSA varied among the three groups. CONCLUSIONS: The volume and the most constricted cross-sectional area of the airway varied with different anteroposterior skeletal patterns. The NA volume of Class I and Class III subjects was significantly larger than that of patients with a Class II skeletal pattern.

Is the prognostic impact of tumor location in patients with surgically resected esophageal squamous cell carcinoma affected by surgical approach?

AIM: The aim of the present study was to clarify differences in node metastasis mode and clinical outcomes based on tumor location in patients with esophageal squamous cell carcinoma (ESCC). PATIENTS AND METHODS: Participants comprised 228 patients with ESCC who underwent radical esophagectomy without preoperative supplement therapies. Lymph nodes were harvested from three fields: the neck, thorax, and abdomen. Patients were divided into three groups depending on tumor location [upper esophagus (UE), middle esophagus, or lower esophagus (LE)] and analyzed clinicopathologically. RESULTS: The LE group showed significantly more progressive ESCC in terms of tumor invasion (p = 0.025), node metastasis (p = 0.0071), and TNM stage (p = 0.0043). The LE group revealed a tendency to metastasize to extrathoracic (especially abdominal) nodes (p = 0.0008). Recurrent laryngeal node metastasis was increased in the UE group (p = 0.016). However, no prognostic differences were detected between groups according to tumor location. Likewise, subgroup analyses by surgical approach (open thoracotomy vs. thoracoscopy) and cancer stage (stage I/II, III, and IV) did not reveal any significant prognostic impact of tumor location. CONCLUSION: Lymphatic spread varied by tumor location, but no prognostic impact of tumor location could be detected in patients with ESCC in spite of surgical approach or cancer stage.

Medical emergency education using a robot patient in a dental setting.

INTRODUCTION: In an ageing society, the frequency of medical emergencies in a dental setting appears to be increasing because of a growing number of medically compromised patients. However, we currently have no dental-specific simulation environment with advanced reproducibility for medical emergencies. Therefore, we used the robot patient in objective structured clinical examinations (OSCEs) for testing student competence in emergency management. This study aimed to evaluate student responses to medical emergencies in the dental setting. MATERIAL AND METHODS: We used 98 fifth-grade dental students at Showa University as subjects and implemented the OSCE task entitled 'Management of medical emergency using a robot patient'. Candidates were asked to manage an emergency situation immediately after local anaesthesia, with one robot patient configured to develop vasovagal syncope and the other to experience adrenaline hypersensitivity. A questionnaire on the educational value of the robot patient was completed after the examination. RESULTS: Thirty-two per cent of students could not accurately count her pulse because of an inappropriate method. Moreover, 78% could not correctly attach either the tonometer or pulse oximetry to the patient. Accurate diagnoses were given by only 22% of students, with vasovagal syncope diagnosed by 33% and adrenaline hypersensitivity by 8%. From a questionnaire, 78% of students recognised the usefulness of the robot patient in medical emergency training. CONCLUSION: We found that student responses to the emergency situation were poor. The robot patient is useful in dental education for medical emergency training and assessment not only for situation management but also for differential diagnosis.

A case of breast milk-acquired cytomegalovirus infection in an extremely low birth weight infant.

INTRODUCTION: Although breast milk is considered the optimal nutrition for infants, it is also the primary cause of postnatal cytomegalovirus (CMV) infection. Preterm infants with postnatal CMV infections are susceptible to a variety of life-threatening conditions. CASE SUMMARY: Twin male infants were delivered via emergency caesarian section at 27 weeks' gestation secondary to maternal complete uterine rupture. The Apgar scores at 1 and 5 min were 1 and 1 for the older twin (Twin A) and 0 and 3 for the younger twin (Twin B). Their birth weights were 1203 g (+ 0.65SD) and 495 g (- 3.79SD) respectively. On day 41, laboratory blood test results for Twin B showed a moderate elevation in C-reactive protein (CRP), thrombocytopenia. CMV quantitative polymerase chain reaction (qPCR) tests in Twin B's urine and blood as well as in the mother's breast milk were positive, but stored, dried umbilical cord CMV qPCR tests were negative. Twin B was diagnosed with a postnatal CMV infection secondary to infected breast milk and ganciclovir was commenced on day 52. Treatment was switched to valganciclovir at 74 days of age, but a negative CMV-DNA level in the blood was not achieved. Postnatal CMV infection in this infant led to an exacerbation of pre-existing bronchopulmonary dysplasia (BPD) and he demised at 182 days of age. CONCLUSION: Postnatal cytomegalovirus infections may lead to exacerbations of BPD. Early use of raw breast milk in preterm infants should be done with careful consideration of this potential complication.

Serum leptin levels negatively correlate with trabecular bone mineral density in high-fat diet-induced obesity mice.

OBJECTIVES: This study evaluated the influence of diet-induced obesity on bone tissue quantity and quality in the proximal tibiae of growing mice and also examined the relationships between the serum total cholesterol, leptin, and adiponectin levels and trabecular and cortical bone mineral parameters. METHODS: Six-week-old male C57BL/6J mice were divided into two groups; one received a control diet, and the other received a high-fat-diet. After treatment for 4, 8, or 12 weeks, the bone quantity and quality were analyzed using peripheral quantitative computed tomography (pQCT), micro-computed tomography and histomorphometry. RESULTS: In the early stages, trabecular bone density decreased with an increase in the number of adipocytes and the deterioration of trabeculae. In contrast, although cortical bone formation was slower in obese mice compared with control mice, bone formation on the periosteal surface increased with age. Serum leptin levels were correlated with trabecular, but not cortical bone density, whereas neither the adiponectin nor total cholesterol level was correlated with bone mass in mice with diet-induced obesity. CONCLUSIONS: We conclude that bone loss at these two sites is differentially regulated in mice. Furthermore, we demonstrate that serum leptin may be a useful indicator of risk for osteoporosis associated with diet-induced obesity.

Introduction of a robot patient into dental education.

In recent years, with the increasing social awareness of safety in medical practice, improving clinical skills has become very important, especially for recently graduated dentists. Traditionally, mannequins have been used for clinical skill training, but a mannequin is quite different from a real patient because they have no autonomous movement or conversational ability. This indicates that pre-clinical simulation education is inadequate. We have, therefore, developed a robot patient that can reproduce an authentic clinical situation for dental clinical training. The robot patient, designed as a full-body model with a height of 157 cm, has eight degrees of freedom in the head and the ability to perform various autonomous movements. Moreover, saliva secretion and conversation with the trainee can be reproduced. We have introduced the robot patient into an objective structured clinical examination targeted at fifth-grade students in our dental school to evaluate their skills in cavity preparation, whilst considering the safety of the treatment. As a result, many of the students were able to deal appropriately with a patient's unexpected movement. Moreover, results of a questionnaire survey showed that almost all the students recognised the educational value of the robot patient especially for 'risk management', and they preferred the robot patient to traditional mannequins. Practical application of the robot patient in dental clinical education was evaluated through the experiences of the fifth-grade students, which showed the effectiveness of the robot patient in the dental field.

The oral microbiome in alcohol use disorder: a longitudinal analysis during inpatient treatment.

BACKGROUND: Alcohol use disorder (AUD)-induced disruption of oral microbiota can lead to poor oral health; there have been no studies published examining the longitudinal effects of alcohol use cessation on the oral microbiome. AIM: To investigate the oral microbiome during alcohol cessation during inpatient treatment for AUD. METHODS: Up to 10 oral tongue brushings were collected from 22 AUD patients during inpatient treatment at the National Institutes of Health. Alcohol use history, smoking, and periodontal disease status were measured. Oral microbiome samples were sequenced using 16S rRNA gene sequencing. RESULTS: Alpha diversity decreased linearly during treatment across the entire cohort (P = 0.002). Alcohol preference was associated with changes in both alpha and beta diversity measures. Characteristic tongue dorsum genera from the Human Microbiome Project such as Streptococcus, Prevotella, Veillonella and Haemophilus were highly correlated in AUD. Oral health-associated genera that changed longitudinally during abstinence included Actinomyces, Capnocytophaga, Fusobacterium, Neisseria and Prevotella. CONCLUSION: The oral microbiome in AUD is affected by alcohol preference. Patients with AUD often have poor oral health but abstinence and attention to oral care improve dysbiosis, decreasing microbiome diversity and periodontal disease-associated genera while improving acute oral health.

Verification of the Usefulness of an Assessment and Risk Control Sheet that Promotes Management of Cancer Drug Therapy.

Background: Proper management of adverse events is crucial for the safe and effective implementation of anticancer drug treatment. Showa University Hospital uses our interview sheet (assessment and risk control [ARC] sheet) for the accurate evaluation of adverse events. On the day of anticancer drug treatment, a nurse conducts a face-to-face interview. As a feature of the ARC sheet, by separately describing the symptoms the day before treatment and the day of treatment and sharing the information on the medical record, it is possible to clearly determine the status of adverse events. In this study, we hypothesized that the usefulness and points for improvement of the ARC sheet would be clarified by using and evaluating a patient questionnaire. Methods: This study included 174 patients (144 at Showa University Hospital (Hatanodai Hospital) and 30 at Showa University Koto Toyosu Hospital (Toyosu Hospital) who underwent pre-examination interviews by nurses and received cancer chemotherapy at the outpatient center of Hatanodai and Toyosu Hospital. In the questionnaire survey, the ARC sheet's content and quality, respondents' satisfaction, structural strengths, and points for improvement were evaluated on a five-point scale. Results: The patient questionnaire received responses from 160 participants, including the ARC sheet use group (132 people) and the non-use group (28 people). Unlike the ARC sheet non-use group, the ARC sheet use group recognized that the sheet was useful to understand the adverse events of aphthous ulcers (p = 0.017) and dysgeusia (p = 0.006). In the satisfaction survey questionnaire, there was a high sense of security in the pre-examination interviews by nurses using the ARC sheet. Conclusions: The ARC sheet is considered an effective tool for comprehensively evaluating adverse events. Pre-examination interviews by nurses using ARC sheets accurately determined the adverse events experienced by patients with anxiety and tension due to confrontation with physicians.

Synaptic pruning of murine adult-born neurons by microglia depends on phosphatidylserine.

New neurons, continuously added in the adult olfactory bulb (OB) and hippocampus, are involved in information processing in neural circuits. Here, we show that synaptic pruning of adult-born neurons by microglia depends on phosphatidylserine (PS), whose exposure on dendritic spines is inversely correlated with their input activity. To study the role of PS in spine pruning by microglia in vivo, we developed an inducible transgenic mouse line, in which the exposed PS is masked by a dominant-negative form of milk fat globule-EGF-factor 8 (MFG-E8), MFG-E8D89E. In this transgenic mouse, the spine pruning of adult-born neurons by microglia is impaired in the OB and hippocampus. Furthermore, the electrophysiological properties of these adult-born neurons are altered in MFG-E8D89E mice. These data suggest that PS is involved in the microglial spine pruning and the functional maturation of adult-born neurons. The MFG-E8D89E-based genetic approach shown in this study has broad applications for understanding the biology of PS-mediated phagocytosis in vivo.

Postsynaptic spiking homeostatically induces cell-autonomous regulation of inhibitory inputs via retrograde signaling.

Developing neural circuits face the dual challenge of growing in an activity-induced fashion and maintaining stability through homeostatic mechanisms. Compared to our understanding of homeostatic regulation of excitatory synapses, relatively little is known about the mechanism mediating homeostatic plasticity of inhibitory synapses, especially that following activity elevation. Here, we found that elevating neuronal activity in cultured hippocampal neurons for 4 h significantly increased the frequency and amplitude of mIPSCs, before detectable change at excitatory synapses. Consistently, we observed increases in presynaptic and postsynaptic proteins of GABAergic synapses, including GAD65, vGAT, and GABA(A)Rα1. By suppressing activity-induced increase of neuronal firing with expression of the inward rectifier potassium channel Kir2.1 in individual neurons, we showed that elevation in postsynaptic spiking activity is required for activity-dependent increase in the frequency and amplitude of mIPSCs. Importantly, directly elevating spiking in individual postsynaptic neurons, by capsaicin activation of overexpressed TRPV1 channels, was sufficient to induce increased mIPSC amplitude and frequency, mimicking the effect of elevated neuronal activity. Downregulating BDNF expression in the postsynaptic neuron or its extracellular scavenging prevented activity-induced increase in mIPSC frequency, consistent with a role of BDNF-dependent retrograde signaling in this process. Finally, elevating activity in vivo by kainate injection increased both mIPSC amplitude and frequency in CA1 pyramidal neurons. Thus, spiking-induced, cell-autonomous upregulation of GABAergic synaptic inputs, through retrograde BDNF signaling, represents an early adaptive response of neural circuits to elevated network activity.

Activity-dependent localization in spines of the F-actin capping protein CapZ screened in a rat model of dementia.

Actin reorganization in dendritic spines is hypothesized to underlie neuronal plasticity. Actin-related proteins, therefore, might serve as useful markers of plastic changes in dendritic spines. Here, we utilized memory deficits induced by fimbria-fornix transection (FFT) in rats as a dementia model to screen candidate memory-associated molecules by using a two-dimensional gel method. Comparison of protein profiles between the transected and control sides of hippocampi after unilateral FFT revealed a reduction in the F-actin capping protein (CapZ) signal on the FFT side. Subsequent immunostaining of brain sections and cultured hippocampal neurons revealed that CapZ localized in dendritic spines and the signal intensity in each spine varied widely. The CapZ content decreased after suppression of neuronal firing by tetrodotoxin treatment in cultured neurons, indicating rapid and activity-dependent regulation of CapZ accumulation in spines. To test input specificity of CapZ accumulation in vivo, we delivered high-frequency stimuli to the medial perforant path unilaterally in awake rats. This path selectively inputs to the middle molecular layer of the dentate gyrus, where CapZ immunoreactivity increased. We conclude that activity-dependent, synapse-specific regulation of CapZ redistribution might be important in both maintenance and remodeling of synaptic connections in neurons receiving specific spatial and temporal patterns of inputs.

Orthodontic treatment of a unilateral impacted mandibular canine and first premolar: a case report.

BACKGROUND: Few dentists have seen an impacted mandibular canine and first premolar, and there is little information in the literature on the treatment of this rare condition. CASE REPORT: A 13-year-old Japanese male with an impacted mandibular right canine and first premolar was treated orthodontically. We discuss both the surgical and orthodontic options and present the successful orthodontic correction of a unilaterally impacted mandibular canine and first premolar.

Impact of the Coronavirus Disease 2019 Outbreak on Activity and Exercise Levels among Older Patients.

OBJECTIVES: This study aimed to clarify the impact of the coronavirus disease 2019 outbreak on the levels of activity among older patients with frailty or underlying diseases. A total of 175 patients (79.0±7.0 years) undergoing outpatient or home-based rehabilitation, stratified into groups, based on frailty status. The percentage of patients who went out at least once a week decreased after the outbreak from 91% to 87%, from 65% to 46%, and from 47% to 36% in the non-frail, frail, and nursing care requirement groups, respectively. The proportion of older patients participating in exercise during the outbreak was 75%, 51%, and 41% in the non-frail, frail, and nursing care requirement groups, respectively. The proportion of older patients participating in voluntary exercise after instruction was lowest in the frail group (35%). Older patients with frailty are susceptible to the negative effects of refraining from physical activity and require careful management.

The V-J recombination of T cell receptor-gamma genes is blocked in interleukin-7 receptor-deficient mice.

IL-7R-deficient mice have severely impaired expansion of early lymphocytes and lack gamma delta T cells. To elucidate the role of IL-7R on gamma delta T cell development, we analyzed the rearrangements of TCR-alpha, beta, gamma, and delta genes in the thymus of the IL-7R-deficient mice. Southern blot analysis with a J gamma 1 probe revealed that more than 70% of J gamma 1 and J gamma 2 alleles are recombined to form distinct V gamma 1.2-J gamma 2 and V gamma 2-J gamma 1 fragments in control mice. On the contrary, no such recombination was detected in the mutant mice. The rearrangements in the TCR-alpha, beta, and delta loci were comparably observed in control and mutant mice. PCR analysis indicated that the V-J recombination of all the V gamma genes is severely hampered in the mutant mice. The mRNA of RAG-1, RAG-2, Ku-80, and terminal deoxynucleotidyl transferase (TdT) genes was equally detected between control and mutant thymi, suggesting that the expression of common recombination machinery is not affected. These data demonstrated that the V-J recombination of the TCR gamma genes is specifically blocked in the IL-7R-deficient mice and suggested the presence of highly specific regulation for TCR gamma gene rearrangement.

Immunoglobulin beta signaling regulates locus accessibility for ordered immunoglobulin gene rearrangements.

The antigen receptor gene rearrangement at a given locus is tightly regulated with respect to cell lineage and developmental stage by an ill-defined mechanism. To study the possible role of precursor B cell antigen receptor (pre-BCR) signaling in the regulation of the ordered immunoglobulin (Ig) gene rearrangement during B cell differentiation, a newly developed system using mu heavy (H) chain membrane exon (microm)-deficient mice was employed. In this system, the antibody-mediated cross-linking of Igbeta on developmentally arrested progenitor B (pro-B) cells mimicked pre-BCR signaling to induce early B cell differentiation in vivo. Analyses with ligation-mediated polymerase chain reaction revealed that the Igbeta cross-linking induced the redirection of Ig gene rearrangements, namely, the suppression of ongoing rearrangements at the H chain locus and the activation of rearrangements at the light (L) chain locus. Upon the cross-linking, the kappaL chain germline transcription was found to be upregulated whereas the V(H) germline transcription was promptly downregulated. Notably, this alteration of the accessibility at the H and L chain loci was detected even before the induction of cellular differentiation became detectable by the change of surface phenotype. Thus, the pre-BCR signaling through Igbeta appears to regulate the ordered Ig gene rearrangement by altering the Ig locus accessibility.