Role of the cerebrospinal fluid-contacting nucleus in the descending inhibition of spinal pain transmission.

The brainstem is well recognized as a critical site for integrating descending modulatory systems that both inhibit and facilitate pain at the level of the spinal cord. The cerebrospinal fluid-contacting nucleus (CSF-contacting nucleus) distributes and localizes in the ventral periaqueductal central gray of the brainstem. Although emerging lines of evidence suggest that the CSF-contacting nucleus may be closely linked to transduction and regulation of pain signals, the definitive role of the CSF-contacting nucleus in pain modulation remains poorly understood. In the present study, we determined the role of the CSF-contacting nucleus in rat nocifensive behaviors after persistent pain by targeted ablation of the CSF-contacting nucleus in the brainstem using the cholera toxin subunit B-saporin (CB-SAP), a cytotoxin coupled to cholera toxin subunit B. Compared with CB/SAP, CB-SAP induced complete ablation of the CSF-contacting nucleus, and the CB-SAP-treated rats showed hypersensitivity in responses to acute nociceptive stimulation, and exacerbated spontaneous nocifensive responses induced by formalin, thermal hyperalgesia and mechanical allodynia induced by plantar incision. Furthermore, immunohistochemical experiments showed that the CSF-contacting nucleus was a cluster of 5-HT-containing neurons in the brainstem, and the spinal projection of serotonergic axons originating from the CSF-contacting nucleus constituted the descending 5-HT pathway to the spinal cord. CB-SAP induced significant downregulation of 5-HT in the spinal dorsal horn, and intrathecal injection of 5-HT significantly reversed hypersensitivity in responses to acute nociceptive stimulation in the CB-SAP-treated rats. These results indicate that the CSF-contacting nucleus 5-HT pathway is an important component of the endogenous descending inhibitory system in the control of spinal nociceptive transmission.

A quantum chemistry study on thermochemical properties of high energy-density endothermic hydrocarbon fuel JP-10.

The density functional theory (DFT) calculations at the M06-2X/6-31++G(d,p) level have been performed to explore the molecular structure, electronic structure, C-H bond dissociation enthalpy, and reaction enthalpies for five isodesmic reactions of a high energy-density endothermic hydrocarbon fuel JP-10. On the basis of the calculations, it is found that the carbonium ion C-6 isomer formed from the catalytic cracking at the C6 site of JP-10 has the lowest energy, and the R-5 radical generated from the thermal cracking at the C5 site of JP-10 is the most stable isomer. Furthermore, a series of hypothetical and isodesmic work reactions containing similar bond environments are used to calculate the reaction enthalpies for target compounds. For the same isodesmic reaction, the reaction enthalpy of each carbon site radical has also been calculated. The present work is of fundamental significance and strategic importance to provide some valuable insights into the component design and energy utilization of advanced endothermic fuels.

A DFT study on the thermal cracking of JP-10.

Density functional theory (DFT) calculations have been carried out to investigate the thermal cracking pathways of JP-10, a high energy density hydrocarbon fuel. Thermal cracking mechanisms are proposed, as supported by our previous experimental results (Xing et al. in Ind Eng Chem Res 47:10034-10040, 2008). Using DFT calculations, the potential energy profiles of the possible thermal cracking pathways for all of the diradicals obtained from homolytic C-C bond cleavage of JP-10 were derived and are presented here. The products of the different thermal cracking pathways are in good agreement with our previous experimental observations.

[Observation on the fluid resuscitation and the change in blood sodium of severely burned patients in the early stage].

OBJECTIVE: To study the necessary amount of fluid consisting of electrolyte and colloid, the ratio of electrolyte and colloid used, and the change of blood sodium during early resuscitation in severely burned patients. METHODS: Sixty-seven patients with total burn surface area (TBSA) equal to or over 70% and full-thickness area equal to or over 50%TBSA, hospitalized from March 2004 to March 2009, were resuscitated with fluid. The infusion amount of electrolyte, colloid, and water, and urinary output of patients at post injury hour (PIH) 24, 48, and 72 were analyzed retrospectively. The variation in blood sodium and fluid infusion at different time points was recorded. Data were processed with SPSS 13.0 software. RESULTS: Among the 67 patients, hyponatremia occurred in 9 cases, hypernatremia occurred in 5 cases, and 53 patients had normal blood sodium level. The urinary output of patients within PIH 72 was above 70 mL/h. K value was calculated through the formula: actual total infusion amount of electrolyte and colloid (mL) = burn area (%TBSA) x body weight (kg) x K. In the first 24 PIH, K value was about 1.7, and the ratio of electrolyte and colloid was 1.4. In the second 24 PIH, K value was about 1.3 with electrolyte and colloid ratio 1.6. K value in the third 24 PIH was about 0.9 with electrolyte and colloid ratio 2.0. CONCLUSIONS: The actual amount of resuscitation fluid is slightly larger than that calculated from traditional formula during the early stage in severely burned patients. The amount of electrolytes and the proportion of electrolyte and colloid will influence blood sodium level of patients.

[Influence of vacuum-assisted closure technique on expression of Bcl-2 and NGF/NGFmRNA during wound healing].

OBJECTIVE: To explore the influence of vacuum-assisted closure technique (VAC) on expression of Bcl-2 and NGF during wound healing. METHODS: Eighty Sprague-Dawley rats were randomly divided into 4 groups with 20 rats of each. Group T was the experimental group; group C1, C2 and C3 were the control groups. In group T and group C1, capsaicin was injected subcutaneously to the back of the rats to destroy the sensory nerve. VAC was employed to the wound of the rats in group T and C2 three times a day at 80 mmHg negative pressure. In all the groups, tissue samples were taken from the wound edge and granulation at 1, 3, 6, 9 and 12 days after the injury. Immunohistochemistry and in situ hybridization were used to detect the expression of Bcl-2 and NGF/NGFmRNA in the samples. RESULTS: In group C2 and C3, the expression of Bcl-2 and NGF/NGFmRNA was obvious, which increased gradually and reached the peak at the 9th day. In the process of wound healing, the expression Bcl-2 and NGF/NGFmRNA was higher in the group C2 than in group C3 (P < 0.05). The expression Bcl-2 and NGF/NGFmRNA in group T and C1 was lower than group C2 and C3 (P < 0.05). CONCLUSION: The application of the vacuum-assisted closure technique during wound healing increases the expression of the apoptosic modulation related protein Bcl-2 and affects the expression of NGF/NGFmRNA, which may promote the wound healing process.