Rhodococcus equi in the soil environment of horses in Inner Mongolia, China

Little is known about the distribution of Rhodococcus equi in the soil environment of native horses in China. One hundred and eight soil samples were collected from native-horse farms in the Hulun Beier grasslands of eastern Mongolia, the Xilin Goler grasslands of southern Mongolia, and Tongliao City in Inner Mongolia, China. The isolation rates of R. equi from soil samples from the Hulun Beier and Xilin Goler grasslands ranged from 25.9% to 30.0%. In contrast, isolation rates from soil samples from Tongliao City were as high as 82.3% and the mean number of R. equi in soil samples from Tongliao City was 10 times more than those of samples from the grasslands. The 488 isolates were examined using PCR for the presence of genes that encode virulence-associated 15-17 kDa antigen protein (VapA) and the 20 kDa antigen protein (VapB). All isolates were negative for virulence-associated proteins. Plasmid profiles of these avirulent isolates showed that cryptic plasmids of various sizes were present with an incidence of 13.3% to 21.5%. The results of the present study contrast with those of our recent study (J. Vet. Med. Sci. 67:611-613, 2005), in which we reported that R. equi was absent from Mongolian horses in Ulaanbaatar, Mongolia. It is suggested that the difference between the results of these two studies is due to the mobile pasturing system in Mongolia and nonmobile pasturing system in Inner Mongolia.

Concanavalin A, ribose, and adenine resuscitate preserved rat hearts

Preserved hearts may have cardiac dysfunction associated with inadequate myocardial high-energy phosphates. To resuscitate preserved hearts, hearts from male Wistar adult rats were preserved in 4.0 degrees C cold-modified Krebs-Henseleit buffer (pH 7.40) for 8 h, subjected to 30 min of reperfusion at 36.5 degrees C with the administration of concanavalin A (Con A; 40 mg/L), ribose (0.1 mM), and adenine (0.1 mM). In comparison with the normal control, the preserved group had a decrease in cardiac output (CO; p < 0.001), myocardial adenosine triphosphate (ATP; p < 0.001), and creatine phosphate (CP; p < 0.001), associated with an increase in myocardial Ca2+ (p < 0.01) and release of myocardial adenine nucleosides (ANs; p < 0.001). In comparison with the preserved group, the group reperfused with ribose and adenine had no improvement of these parameters (p > 0.05). The group reperfused with Con A had an increase in CO (p < 0.01) and myocardial CP (p < 0.01), associated with a decrease in myocardial Ca2+ (p < 0.05) and ANs release (p < 0.01), and no change in myocardial ATP. However, the group reperfused with Con A, ribose, and adenine achieved a significant increase in CO (p < 0.005), ATP (p < 0.005), CP (p < 0.005), and a decrease in myocardial Ca2+ (p < 0.01) and ANs release (p < 0.01). Data suggest that the combination of Con A, ribose, and adenine may resuscitate cold-preserved rat hearts.

Beneficial effects of fluosol-polyethylene glycol cardioplegia on cold, preserved rabbit heart

BACKGROUND

Because of its high oxygen-carrying capacity, especially at low temperatures, fluosol may enhance heart preservation.

METHODS

Hearts of male New Zealand white rabbits (1.5-2.0 kg) were excised and flushed through the aorta with 0 degree C St. Thomas' Hospital solution, fluosol, or polyethylene glycol or fluosol-polyethylene glycol cardioplegic solution. Hearts were then stored for 12 hours at 0 degree C and reperfused with Krebs-Henseleit buffer at 36.5 degrees C for 60 minutes using a Langendorff system.

RESULTS

Myocardial contractile function was significantly greater in the fluosol-polyethylene glycol cardioplegia-preserved group (p < 0.01) and polyethylene glycol-cardioplegia preserved group (p < 0.05) than in the St. Thomas' Hospital solution-preserved group. The myocardial high-energy phosphate content was significantly higher in the fluosol-polyethylene glycol-cardioplegia-preserved group (p < 0.01), with reduced release of lactate dehydrogenase (p < 0.01) in comparison with the St. Thomas' Hospital solution-preserved group.

CONCLUSIONS

The addition of fluosol and polyethylene glycol to the cardioplegic solution may enhance long-term cold heart preservation.

Verapamil, ribose and adenine enhance resynthesis of postischemic myocardial ATP

Acute postischemic cardiac dysfunction was studied in isolated reperfused rat hearts. Postischemic administration of neither verapamil nor ribose and adenine resulted in an increase of myocardial ATP content. However, administration of verapamil combined with ribose and adenine achieved an enhanced recovery of high-energy phosphates.

Ruthenium red, ribose, and adenine enhance recovery of reperfused rat heart

BACKGROUND

Postischemic cardiac failure may be associated with inadequate storage of myocardial adenosine triphosphate (ATP). ATP precursors were administered to resuscitate the postischemic myocardium.

METHODS

Hearts isolated from male Wistar adult rats were perfused with Krebs-Henseleit buffer (pH, 7.40), subjected to 30 minutes of global ischemia at 36 degrees C, followed by 30 minutes of retrograde reperfusion with the postischemic intervention of ruthenium red (1 microM), ribose (1 mM), and adenine (1 mM). Multiple analysis of variance was used to compare means between groups (eight rats in each group).

RESULTS

In comparison with the nonischemic group, the postischemic nontreated group had a decrease in the maximum rate of left ventricular pressure rise (+dP/dt, P < 0.0005) and level of myocardial ATP (P < 0.0005) but an increase in level of mitochondrial Ca2+ (P < 0.005). In comparison with the nontreated group, ribose and adenine had no effect on all the above-mentioned parameters, and ruthenium red elevated maximum left ventricular +dP/dt (P < 0.05) and reduced mitochondrial Ca2+ (P < 0.05) with no change in ATP (P > 0.05). However, ruthenium red with ribose and adenine achieved a significant increase in maximum left ventricular +dP/dt (P < 0.0005), ATP levels (P < 0.005), and a decrease in levels of mitochondrial Ca2+ (P < 0.005).

CONCLUSION

Acute postischemic cardiac failure may be related to Ca2+ overload in mitochondria. Ruthenium red may reduce mitochondrial Ca2+ overload. Ruthenium red, ribose, and adenine in combination may be capable of enhancing the recovery of myocardial high-energy phosphates and mechanical function in the postischemic myocardium.

Concanavalin A enhances ATP resynthesis via de novo pathway in postischemic rat hearts

Acute post-ischemic cardiac failure was studied in isolated rat hearts. Xylitol, glutamine, aspartic acid and glycine were added during reperfusion, resulting in no inotropic effect. Concanavalin A had a moderate inotropic effect. When concanavalin A added with xylitol, glutamine, aspartic acid and glycine, a rapid recovery of myocardial function and high-energy phosphate was achieved.

Oxygen-dependent lipid peroxidation during lung ischemia

The effect of alveolar oxygen tension on lung lipid peroxidation during lung ischemia was evaluated by using isolated rat lungs perfused with synthetic medium. After a 5-min equilibration period, global ischemia was produced by discontinuing perfusion while ventilation continued with gas mixtures containing 5% CO2 and a fixed oxygen concentration between 0 and 95%. Lipid peroxidation was assessed by measurement of tissue thiobarbituric acid-reactive products and conjugated dienes. Control studies (no ischemia) showed no change in parameters of lipid peroxidation during 1 h of perfusion and ventilation with 20% or 95% O2. With 60 min of ischemia, there was increased lipid peroxidation which varied with oxygen content of the ventilating gas and was markedly inhibited by ventilation with N2. Perfusion with 5-, 8-, 11-, 14-eicosatetraynoic acid indicated that generation of eicosanoids during ischemia accounted for approximately 40-50% of lung lipid peroxide production. Changes of CO2 content of the ventilating gas (to alter tissue pH) or of perfusate glucose concentration had no effect on lipid peroxidation during ischemia, but perfusion at 8% of the normal flow rate prevented lipid peroxidation. Lung dry/wet weight measured after 3 min of reperfusion showed good correlation between lung fluid accumulation and lipid peroxidation. These results indicate that reperfusion is not necessary for lipid peroxidation with ischemic insult of the lung and provide evidence that elevated PO2 during ischemia accelerates the rate of tissue injury.

Postnatal changes in enzyme activities of rat myocardial adenine nucleotide catabolic pathway

Three catabolic enzymes, 5'-nucleotidase (5'NT), adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP) and one anabolic enzyme, myokinase (MK) involved in adenine nucleotide (AN) metabolism were studied in myocardium from 4 to 105 day old rats. The specific enzyme activities (nmoles/min/mg protein) at day 4 were 35.3 for 5'NT, 28.4 for ADA, 43.3 for PNP, and 5 X 10(3) for MK. At day 7, 5'NT, activities rose to 450%; PNP and ADA 150%; and MK 120%; of the day 4 level. The activities of the three catabolic enzymes were elevated for one or two weeks then declined rapidly. By day 34, they were slightly above the adult values. MK activity displayed a different time course. It continued to increase slowly with age after the initial surge. Compared to the adult heart, the total activities of these catabolic enzymes in the one- to three-week-old heart were 30% to 220% higher. This transient elevation in AN catabolic enzyme activities may be related to active DNA synthesis and cell proliferation occurred in the rat myocardium during the same period.