Establishment of a rat model of type II diabetic neuropathic pain.

OBJECTIVE: To establish a rat model of type II diabetic neuropathic pain. METHODS: Sixty Sprague Dawley rats were randomly divided into two groups: group A (N = 10) was fed a normal diet, and group B (N = 50) was fed a high-fat and high-sugar diet. After 8 weeks, the body weight of all rats was recorded, and rats in both groups had their fasting plasma glucose, insulin concentration, and insulin sensitivity index measured and calculated. Subsequently, the rats in group B were randomly divided into three subgroups that were each given different doses of streptozotocin (STZ) by a single intraperitoneal injection (subgroup B1 received 30 mg/kg, subgroup B2 received 35 mg/kg, and subgroup B3 40 mg/kg). Two weeks after the STZ injection, the four groups of rats had their insulin sensitivity index, mechanical withdrawal threshold, and thermal withdrawal latency assessed, allowing us to establish a rat model of type II diabetic neuropathic pain and to determine the optimum dose of STZ. Four weeks after STZ injection (2 weeks after the model was established), the pain threshold was measured in the rats in group A and the group treated with the most effective STZ dose. We also measured the expression of phosphorylated extracellular signal-regulated kinase (p-ERK), phosphorylated cyclic AMP response element-binding protein (p-CREB), and phosphorylated N-methyl d-aspartate receptor subtype B (p-NR2B) in the dorsal root ganglion (DRG) and spinal cord dorsal horn regions, which are closely related to neuropathic pain, and also recorded the TTX-R sodium currents in the acutely isolated DRG neurons. RESULTS: After 8 weeks of a high-fat, high-sugar diet, the body weight of the rats in group B was significantly increased. Although the fasting blood glucose levels did not change significantly, the fasting insulin levels were slightly elevated, and the insulin sensitivity index was significantly reduced. Two weeks after STZ injection, the blood glucose levels of the rats in subgroup B1 were elevated but did not remain so for a prolonged period. In contrast, the rats in subgroup B3 had elevated blood glucose that was accompanied by a high mortality rate, while the blood glucose levels of the rats in subgroup B2 were moderately elevated and relatively stable. In addition, the pain threshold was significantly decreased (P < 0.05), and the mortality was low in this group. Because of this, the dose of STZ that was used in group B2 was considered the most effective dose of STZ for induction of diabetes. Four weeks after STZ injection, the pain threshold in the rats of group B2 was still significantly decreased, and the expression of p-ERK, p-CREB, and p-NR2B in the dorsal root ganglion (DRG) and spinal cord dorsal horn was significantly increased. The tetrodotoxin-resistant sodium current density in DRG neurons was also significantly elevated (P < 0.05). CONCLUSIONS: A rat model of type II diabetic neuropathic pain can be established by feeding rats a high-fat, high-sugar diet for 8 weeks, in combination with intraperitoneal injection of 35 mg/kg STZ. This model can be stably maintained for at least 2 weeks.

A highly sensitive electrochemiluminescence immunoassay for detecting human embryonic human chorionic gonadotropin in spent embryo culture media during IVF-ET cycle.

PURPOSE: To investigate the stability and repeatability of electrochemiluminescence immunoassay (ECLIA) for beta-hCG detection in embryo spent culture media. To evaluate the correlation between the viability of preimplantation embryo and beta-hCG profile by the new assay. METHODS: In a retrospective study, a total of 357 spent culture media from day1 to day5 were individually collected and quantified by ECLIA. The blank controls and reliability test were performed with normal saline/pure culture media. RESULTS: 1) There was no detectable amount of beta-hCG in blank controls. A high degree of linearity (R(2) = 0.995) was found in this study; intra-assay and inter-assay coefficient of variation were 4.87 % and 6.25 %. 2) A significantly higher concentration of beta-hCG was found at day5 group than it at day3 group, both in total samples (1.47 ± 0.68mIU/ml vs 0.55 ± 0.32mIU/ml) and in homologous embryo samples (1.43 ± 0.91mIU/ml vs 0.52 ± 0.23mIU/ml). 3) There was a positive correlation between beta-hCG concentration and implantation rate (r = 0.559 at day3 and 0.535 at day5) or blastocyst morphological grading (r = 0.411). CONCLUSIONS: ECLIA may be an optimal choice for detecting beta-hCG in spent culture media to assess embryo viability, indicating secreted beta-hCG as a useful biomarker for embryo selection in IVF-ET procedure.