A rat model for inducing temporomandibular anterior disc displacement experimentally.

The aim of this study was to establish an experimental rat model of temporomandibular joint (TMJ) anterior disc displacement (ADD). A pilot study was conducted to determine the most appropriate surgical protocol. In the main experiment, 40 rats were used. Twenty-four rats were subjected to ADD in the right TMJ, and subsequently thereafter six, nine, and nine rats were sacrificed at 1, 4, and 8 weeks, respectively, for gross evaluation. Twelve rats that underwent a sham operation were equally divided and sacrificed at each of the above time points. Four non-treated control rats were sacrificed at the beginning of the study. TMJ blocks were harvested for radiological and histological assessment. Gross examination showed that 14 rats in the ADD group (58.3%) had anterior displacement of the TMJ disc. In the ADD joints, posterior condylar cartilage thickness decreased during the follow-up period; however, there was no significant difference between the sham-treated and ADD joints, or among the follow-up time points (P > 0.05). The anterior condylar cartilage exhibited obvious qualitative alterations. Radiologic signs of osteoarthrosis appeared after ADD surgery, but this became attenuated with time. The model investigated in this study successfully induced ADD in rats, and should be useful for assessment of progressive changes in the TMJ following ADD.

Development of multiplex PCR assays based on the 16S-23S rRNA internal transcribed spacer for the detection of clinically relevant nontuberculous mycobacteria.

AIMS: To accelerate the identification and differentiation of clinically relevant nontuberculous mycobacteria (NTM) with two sets of multiplex PCR (mPCR) targeting the 16S-23S rRNA internal transcribed spacer (ITS) region for timely patient management. METHODS AND RESULTS: Two mPCR assays were developed: Slow-Growers (SG) mPCR was used for the detection of slow-growing mycobacteria, which included Mycobacterium avium complex, Mycobacterium kansasii, Mycobacterium gordonae and Mycobacterium xenopi whilst the other mPCR assay labelled as Fast-Growers (FG) mPCR was used for the detection of Mycobacterium fortuitum complex, Mycobacterium abscessus and Mycobacterium chelonae. In these assays, a common forward primer based on a conserved section of the 16S rRNA region was used in conjunction with species-specific reverse primers. The mPCRs were tested against 247 clinical mycobacterial isolates and demonstrated 100% specificity and sensitivity. Identification of the mycobacterial species was also validated by DNA sequencing of the 16S-23S ITS region and when further confirmation was needed, hsp65 sequencing was performed. CONCLUSIONS: The mPCR assays could be a potentially useful diagnostic tool for the rapid and accurate identification of clinically relevant NTM. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, we looked at the frequency of hospital isolated NTM over the last 5 years (2005-2010), and an mPCR targeting the ITS region was developed for NTM species that appeared to be more prevalent in the context of Singapore.

Diabetogenic role of insulin's counterregulatory hormones in the isletectomized, diabetic goby.

In an experimental model of insulin-dependent diabetes mellitus (IDDM) in the teleost fish, the goby Gillichthys mirabilis, an isletectomy procedure completely removes the pancreatic endocrine tissue without affecting the exocrine acini or other essential tissues. Interestingly, isletectomized (Ix) gobies do not exhibit a significant hyperglycemia until 10-15 d after this procedure, suggesting a lack of initial diabetogenic actions of a pancreatic factor(s). Administering exogenous glucagon in otherwise nonsymptomatic 7-d Ix gobies, however, induces a hyperglycemic state comparable to that in severely diabetic rats or gobies (after 20 d post-Ix). The spontaneously arising hyperglycemia observed between 10 and 15d post-Ix, on the other hand, is significantly correlated with increasing serum cortisol concentrations, with both exhibiting sustained elevated levels (approx 23 mmol/L and >100 ng/mL, respectively) at 20- and 25-d post-Ix. Exogenous cortisol treatment also significantly induced hyperglycemia in nonsymptomatic, 7-d Ix gobies. By contrast, growth hormone (GH) had no detectable diabetogenic effect in 7-d Ix gobies. Serum levels of ammonia, the principal nitrogenous waste in this species, were not affected by glucagon treatment but were reduced slightly by GH treatment (30% reduction; p < 0.05). Cortisol treatment, on the other hand, increased ammonia levels twofold, suggesting that the glucocorticoid induces a negative nitrogen balance. These results indicate that the counterregulatory hormones--glucagon and cortisol--are effective diabetogenic factors in the Ix goby, capable of driving metabolic imbalance in this model of IDDM.