Enhanced endoplasmic reticulum RyR1 receptor phosphorylation leads to diaphragmatic dysfunction in septic rats / 南方医科大学学报

OBJECTIVE@#To explore the role of endoplasmic reticulum ryanodine receptor 1 (RyR1) expression and phosphorylation in sepsis- induced diaphragm dysfunction.@*METHODS@#Thirty SPF male SD rats were randomized equally into 5 groups, including a sham-operated group, 3 sepsis model groups observed at 6, 12, or 24 h following cecal ligation and perforation (CLP; CLP-6h, CLP-12h, and CLP-24h groups, respectively), and a CLP-24h group with a single intraperitoneal injection of KN- 93 immediately after the operation (CLP-24h+KN-93 group). At the indicated time points, diaphragm samples were collected for measurement of compound muscle action potential (CMAP), fatigue index of the isolated diaphragm and fitted frequencycontraction curves. The protein expression levels of CaMK Ⅱ, RyR1 and P-RyR1 in the diaphragm were detected using Western blotting.@*RESULTS@#In the rat models of sepsis, the amplitude of diaphragm CMAP decreased and its duration increased with time following CLP, and the changes were the most obvious at 24 h and significantly attenuated by KN-93 treatment (P < 0.05). The diaphragm fatigue index increased progressively following CLP (P < 0.05) irrespective of KN- 93 treatment (P>0.05). The frequency-contraction curve of the diaphragm muscle decreased progressively following CLP, and was significantly lower in CLP-24 h group than in CLP-24 h+KN-93 group (P < 0.05). Compared with that in the sham-operated group, RyR1 expression level in the diaphragm was significantly lowered at 24 h (P < 0.05) but not at 6 or 12 following CLP, irrespective of KN-93 treatment; The expression level of P-RyR1 increased gradually with time after CLP, and was significantly lowered by KN-93 treatment at 24 h following CLP (P < 0.05). The expression level of CaMKⅡ increased significantly at 24 h following CLP, and was obviously lowered by KN-93 treatment (P < 0.05).@*CONCLUSION@#Sepsis causes diaphragmatic dysfunction by enhancing CaMK Ⅱ expression and RyR1 receptor phosphorylation in the endoplasmic reticulum of the diaphragm.

Effect of shenmai injection on L-type calcium current of diaphragmatic muscle in rats / 华中科技大学学报（医学）（英德文版）

In this study, whole cell patch clamp recording technique was employed to investigate the effect of Shenmai Injection (SMI) on L-type calcium current of diaphragmatic muscle in rats. The result showed that when the diaphragmatic muscle cell was held at -80 mV and depolarized to +60 mV, 10 microl/ml, 50 microl/ml and 100 microl/ml SMI enhanced the inner peak L-type calcium current from -(6.8 +/- 0.7) pA/pF (n=7) to -(7.3 +/- 0.8) pA/pF (P>0.05, n=7), -(8.6 +/- 1.0) pA/pF (P<0.05, n=7) and -(9.4 +/- 1.2) pA/pF (P<0.05, n=7), respectively, The rates of L-type calcium current were increased by (7.34 +/- 2.37)%, (25.72 +/- 5.94)%, and (38.16 +/- 7.33)%, respectively. However, it had no significant effect on maximal activation potential and reversal potential. Our results suggested that SMI could activate the calcium channel of the diaphragmatic fibers of the rats, increase the influx of Ca2+, and enhance the contractility of diaphragmatic muscles.

Antagonism by hemoglobin of effects induced by L-arginine in neuromuscular preparations from rats

Nitric oxide (NO)-synthase is present in diaphragm, phrenic nerve and vascular smooth muscle. It has been shown that the NO precursor L-arginine (L-Arg) at the presynaptic level increases the amplitude of muscular contraction (AMC) and induces tetanic fade when the muscle is indirectly stimulated at low and high frequencies, respectively. However, the precursor in muscle reduces AMC and maximal tetanic fade when the preparations are stimulated directly. In the present study the importance of NO synthesized in different tissues for the L-Arg-induced neuromuscular effects was investigated. Hemoglobin (50 nM) did not produce any neuromuscular effect, but antagonized the increase in AMC and tetanic fade induced by L-Arg (9.4 mM) in rat phrenic nerve-diaphragm preparations. D-Arg (9.4 mM) did not produce any effect when preparations were stimulated indirectly at low or high frequency. Hemoglobin did not inhibit the decrease of AMC or the reduction in maximal tetanic tension induced by L-Arg in preparations previously paralyzed with d-tubocurarine and directly stimulated. Since only the presynaptic effects induced by L-Arg were antagonized by hemoglobin, the present results suggest that NO synthesized in muscle acts on nerve and skeletal muscle. Nevertheless, NO produced in nerve and vascular smooth muscle does not seem to act on skeletal muscle

A comparative study of aging of the elastic fiber system of the diaphragm and the rectus abdominis muscles in rats

In the present study the age-related changes of the striated muscle elastic fiber system were investigated in the diaphragm and rectus abdominis muscles of 1-, 4-, 8- and 18-month-old rats. The activation patterns of these muscles differ in that the diaphragm is regularly mobilized tens of times every minute during the entire life of the animal whereas the rectus abdominis, although mobilized in respiration, is much less and more irregularly activated. The elastic fibers were stained by the Verhoeff technique for mature elastic fibers. Weigert stain was used to stain mature and elaunin elastic fibers, and Weigert-oxone to stain mature, elaunin and oxytalan elastic fibers. The density of mature and elaunin elastic fibers showed a progressive increase with age, whereas the amount of oxytalan elastic fibers decreased in both diaphragm and rectus abdominis muscles and their muscular fascias. These age-related quantitative and structural changes of the elastic fiber system may reduce the viscoelastic properties of the diaphragm and rectus abdominis muscles, which may compromise the transmission of tensile muscle strength to the tendons and may affect maximum total strength

Evaluación de la vía de absorción linfática durante peritonitis experimentales / Evaluation of lymphatic absortion during experimental peritonitis

Se evaluó la vía linfática de absorción de toxinas durante peritonitis experimentales. Durante la 1a parte de la investigación se controló la cantidad de absorción por vía linfática del Tc 99 en ratas con y sin bloqueo del peritoneo subdiafragmático. En la 2a parte se comprobó la absorción linfática con y sin bloqueo subdiafragmático bajo condiciones de sepsis abdominal en un modelo de asa ileal aislada y desvascularizada. En la 1a parte se observó una disminución significativa de la absorción del radioisótopo en los animales con bloqueo, poniendo de manifiesto la importancia de esta vía. En la 2a parte las diferencias de absorción no fueron significativas probablemente debidos a la hipovalemia en la 1a etapa de la sepsis abdominal. Se destaca el importante rol de la vía linfática subdiafragmática y del conducto torácico en la absorción y transporte de endotoxinas en la sepsis.

Effect of Mn++ on blood sugar level in rats.

Mn++ produced hypoglycemia in normal rats. The effect was dose-dependent. However, Mn++ did not produce hypoglycemia in alloxan-treated rats. There was a rise in liver glycogen following Mn++ treatment which was correlated with fall in blood sugar at 1 1/2 and 3 hr. There was also increase in the glucose uptake by rat diaphragm upto 47% between 2 and 3 hr. The results suggest that functioning, intact pancreatic beta-cells are necessary for the action of Mn++ and that Mn++ may have a peripheral effect on glucose entry into the cells.