[Influences of gas explosion on acute blast lung injury and time phase changes of pulmonary function in rats under real roadway environment].

Objective: The aims of this study were to investigate the effect of gas explosion on rats and to explore the pulmonary function alterations associated with gas explosion-induced acute blast lung injury (ABLI) in real roadway environment. Methods: In April 2018, the large coal mine gas explosion test roadway and explosion test system were used to simulate the real gas explosion roadway environment, fixed the cage and set the explosion parameters. 72 SD rats, male, SPF grade, were randomly divided into nine groups by completely random grouping method according to their body weight: control group, close range group (160 m) , and long range group (240 m) . In each group, there were wound groups (24 h group and 48h group, 8/group, total 48 in six groups) and no wound groups (8/group, total 24 in three groups) . Except for the control group, the other groups were placed in cages at different distances under anesthesia, the experiment of gas explosion was carried out by placing the rats in a position that could force the lungs. The changes of respiratory function of the rats in the non-invasive group were monitored with pulmonary function instrument at 2 h, 24 h, 48 h, 72 h and 168h after the explosion, and were killed under anesthesia 7 days later; the rats in invasive groups were anesthetized and killed at 24 h, 48 h and 168 h, respectively. Gross observation, lung wet-dry ratio and lung histopathology were performed. Results: Compared with the control group, f (respiratory frequency, f) , MV (minute ventilation, MV) , PEF (peak expiratory flow rate, PEF) , PIF (peak inspiratory flow rate, PIF) and EF50 (1/2 tidal volume expiratory flow, EF50) of rats in the close and long range groups decreased significantly after gas explosion 2 h. PAU (respiration pause, PAU) , Te (expiratory time, Te) , Ti (inspiratory time, Ti) and Tr (relaxation time, Tr) were significantly increased (P<0.05) . After 48 h, TV (tidal volume, TV) , Penh (enhanced respiration pause, Penh) , PAU, and PIF of rats in the long range group were significantly increased (P<0.05) . After 72 h, MV in the long range group was significantly decreased (P<0.05) . Compared with the control group, Penh, PAU, Ti and Te were significantly decreased after 168 h in the close and long range groups, with statistical significance (P<0.05) . At the same time, the body weight of rats in different range groups was significantly decreased (P<0.05) . In addition, both HE staining and routine observation of lung tissues of rats in different range groups showed that gas explosion caused pulmonary edema, obviously congested pulmonary capillaries, a large number of inflammatory cells and infiltrated red blood cells. Conclusion: Gas explosion in real roadway environment can cause the change of respiratory function phase and lung tissue damage in rats, suggesting that the model of gas explosion-induced ABLI has been initially established successfully, which would provide a basis for further study on the pathogenesis of ABLI.

Effects of temperature-humidity index and chromium supplementation on antioxidant capacity, heat shock protein 72, and cytokine responses of lactating cows.

Heat stress adversely affects the productivity and immune status of dairy cows. The temperature-humidity index (THI) is commonly used to indicate the degree of heat stress on dairy cattle. We investigated the effects of different THI and Cr supplementation on the antioxidant capacity, the levels of heat shock protein 72 (Hsp72), and cytokine responses of lactating cows. The study used a total of 24 clinically healthy uniparous midlactation Holstein cows, which were randomly divided into 2 groups (n = 12 per group), and was conducted in 3 designated THI periods: low THI period (LTHI; THI = 56.4 ± 2.5), moderate THI period (MTHI; THI = 73.9 ± 1.7), and high THI period (HTHI; THI = 80.3 ± 1.0). The 2 groups of cows were fed corn and corn silage based basal diet supplemented chromium picolinate to provide 3.5 mg of Cr/cow daily (Cr+) or basal diet with no Cr (Cr-). The experiment was a 3 × 2 factorial design. The numbers of leukocytes (P < 0.05) and serum levels of glucose (P < 0.001) were lower; however, the serum levels of blood urea nitrogen (BUN; P < 0.001) and creatinine (P < 0.001) were greater in the MTHI and HTHI than in LTHI. The total antioxidant capacity in the serum was unaltered; an increase in superoxide dismutase activity (P < 0.001) and in serum malondialdehyde concentration (P < 0.001) was observed in the MTHI and HTHI compared with the LTHI. The high THI led to increases in serum concentrations of tumor necrosis factor-α (TNF-α; P < 0.001) and IL-10 (P < 0.05). Cows supplemented with Cr had lower (P = 0.009) serum concentrations of cholesterol but greater (P < 0.001, respectively) serum levels of Hsp72 and IL-10 compared with those without Cr supplementation in the HTHI. Western blot analysis revealed that cows supplemented with Cr had greater (P = 0.038) expression of the inhibitor of nuclear factor kappa B α (IκBα) in peripheral blood mononuclear cells (PBMC) compared with those without Cr supplementation in the HTHI, whereas the expression of Hsp72 in PBMC was unaltered. Data indicate that there is a decrease in glucose and increases in BUN and creatinine in the serum of midlactation cows under hot conditions during the summer and that these cows have a lowered oxidative capacity but an elevated antioxidant capacity. In addition, Cr may play an anti-inflammatory role in lactating cows by promoting the release of Hsp72, increasing the production of IL-10, and inhibiting the degradation of IκBα under hot conditions during the summer.

Short communication: Pheromonicin-SA affects mRNA expression of toll-like receptors, cytokines, and lactoferrin by Staphylococcus aureus-infected bovine mammary epithelial cells.

Pheromonicin-SA (Ph-SA) is a newly developed, engineered multidomain peptide that has a bactericidal effect against Staphylococcus aureus. The objective of this study was to characterize innate immune responses by Staph. aureus-stimulated bovine mammary epithelial cells (BMEC) following treatment with Ph-SA. Primary BMEC from one lactating Holstein cow were isolated and exposed to Staph. aureus for 2 h, and then treated with rifampicin or Ph-SA. Total RNA was isolated from BMEC at 0, 2, 6, 12, and 24 h postinfection, and the mRNA expression of selected genes, including toll-like receptor (TLR)2 and TLR4, IL-1ß, IL-6, IL-8, tumor necrosis factor α (TNF-α), and lactoferrin, was quantified by real-time PCR. In the rifampicin group, increases in the expression of mRNA for TNF-α, IL-1ß, IL-6, IL-8, and lactoferrin were observed at 6 h postinfection and in the expression of mRNA for TLR2 but not for TLR4 at 12 h postinfection. In the Ph-SA group, increases in the mRNA expression of TLR2, TNF-α, IL-1ß, IL-6, IL-8, and lactoferrin were observed at 6 h postinfection, and an increase in TLR4 mRNA expression was observed at 24 h postinfection. At 24 h postinfection, the mRNA expression of TLR4, TNF-α, IL-1ß, IL-6, IL-8, and lactoferrin was higher in the Ph-SA group than in the rifampicin group. In conclusion, Ph-SA might promote the expression of mRNA for TLR2, TLR4, the pro-inflammatory cytokines IL-1, IL-6, and TNF-α, the chemotactic factor IL-8, and lactoferrin in Staph. aureus-infected BMEC. Moreover, Ph-SA may be of value as an antibiotic in promoting innate immune responses by Staph. aureus-infected bovine mammary epithelial cells.

Clonidine-displacing substance reduces glucagon secretion from mouse pancreatic alpha-cells by K(ATP)-channel-independent inhibition of exocytosis.

Clonidine-displacing substance (CDS) is a potent stimulator of insulin release from pancreatic beta-cells and has been suggested to constitute the endogenous ligand for the islet imidazoline-binding site. Here we have explored the effects of CDS on glucagon release from mouse pancreatic alpha-cells. CDS (5 U/ml) produced a 35% inhibition (P < 0.05) of glucagon release from intact islets. This effect was dose-dependent and half-maximal inhibition by CDS was observed at 0.03 U/ml. Inhibition of glucagon release was not associated with a change in whole-cell ATP-sensitive K(+)-channel activity in single alpha-cells. However, during intracellular application through the recording pipette, CDS produced a 36% (P < 0.05) decrease in the rate of exocytosis, measured as changes in cell capacitance. The inhibitory effect of CDS on exocytosis resulted from activation of the protein phosphatase calcineurin and was abolished by cyclosporin A. These data provide further evidence for a role of CDS as an endogenous ligand controlling islet hormone secretion.

Regulation of glucagon release in mouse -cells by KATP channels and inactivation of TTX-sensitive Na+ channels.

The perforated patch whole-cell configuration of the patch-clamp technique was applied to superficial glucagon-secreting alpha-cells in intact mouse pancreatic islets. alpha-cells were distinguished from the beta- and delta-cells by the presence of a large TTX-blockable Na+ current, a TEA-resistant transient K+ current sensitive to 4-AP (A-current) and the presence of two kinetically separable Ca2+ current components corresponding to low- (T-type) and high-threshold (L-type) Ca2+ channels. The T-type Ca2+, Na+ and A-currents were subject to steady-state voltage-dependent inactivation, which was half-maximal at -45, -47 and -68 mV, respectively. Pancreatic alpha-cells were equipped with tolbutamide-sensitive, ATP-regulated K+ (KATP) channels. Addition of tolbutamide (0.1 mM) evoked a brief period of electrical activity followed by a depolarisation to a plateau of -30 mV with no regenerative electrical activity. Glucagon secretion in the absence of glucose was strongly inhibited by TTX, nifedipine and tolbutamide. When diazoxide was added in the presence of 10 mM glucose, concentrations up to 2 microM stimulated glucagon secretion to the same extent as removal of glucose. We conclude that electrical activity and secretion in the alpha-cells is dependent on the generation of Na+-dependent action potentials. Glucagon secretion depends on low activity of KATP channels to keep the membrane potential sufficiently negative to prevent voltage-dependent inactivation of voltage-gated membrane currents. Glucose may inhibit glucagon release by depolarising the alpha-cell with resultant inactivation of the ion channels participating in action potential generation.