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.

[Multiple renal infarction associated with lupus anticoagulant in a patient with systemic lupus erythematosus]

We report a rare case with multiple renal infarction associated with lupus anticoagulant and SLE. A 20-year old woman presented with remitent fever, butterfly rash and, abdominal pain. Laboratory findings showed leukopenia, positive antinuclear and anti-DNA antibodies, and biological false positive for syphilis. Despite a therapy with prednisolone 25 mg/day, the patient showed hypocomplementemia, high titer of anti-DNA antibody and a development of proteinuria and an elevation of serum creatinine. Renal biopsy revealed no abnormalities. She presented abdominal pain with an elevation of serum LDH. Abdominal dynamic computed tomography demonstrated multiple perfusion defects in both kidneys indicating multiple renal infarction. Brain MRI showed multiple micro infarction in the anterior lobes. She was treated with 80 mg of aspirin and have been in remission for two years. Although there have been reported 18 cases with renal infarction associated with antiphospholipid syndrome, this is the first report in Japan. Renal infarction should be differentiated from renal involvement in patients with SLE who have antiphospholipid antibodies.

[Remission induction after pentoxifylline treatment in a patient with rheumatoid arthritis]

Pentoxifylline (POF) has been shown to have anti-inflammatory and immunomodulatory effects. including suppression of TNF-alpha production by activated macrophages, Th-1 response of T cells, and fibroblasts' proliferation and metalloproteinase production. Pentoxifylline was also reported to possess therapeutic properties in 50% of severe refractory RA in an open study. We experienced a 64 year-old man with seronegative RA, stage 2, class 3. He showed 23 swollen joints, 32 painful joints, ADL score 37/40, and ESR 135 mm/h. All these parameters were dramatically improved 3 weeks after administration of POF 300 mg/d and prednisolone 5 mg/d. Discontinuation of POF resulted in rapid exacerbation of RA. POF was restarted and the patient showed complete recovery from arthritis with normalization of ESR within 3 months and was maintained a complete remission for another 1 year. This case further supports a potential antirheumatic effect of POF on some patients with RA.