Hypoxia preconditioning improves structure and function of astrocytes mitochondria via PGC-1α/HIF signal

The protective effect of astrocytes on nerves was demonstrated by mitochondrial transfer. The neuroprotective effect of hypoxic pretreatment is widely accepted. The aim of this research is to investigate the role of hypoxic preconditioning on astrocytes mitochondria. Rat neuronal cells and astrocytes were isolated and cultured. A hypoxic preconditioned astrocyte and oxygen glucose deprivation (OGD) neuronal cell co-culture experiment was used to detect the effect of hypoxic preconditioning (HP) on nerve damage. The silencing of proliferatoractivated receptor γ coactivator-1α (PGC-1α) with siRNA was used to explore the role of HP in the repair of nerve damage and biogenesis of mitochondria. HP increased astrocyte viability and promoted neuroprotective factor secretion. The expression levels of antioxidant enzymes, PGC-1α and uncoupling protein2 (UCP2) were up-regulated by HP. In addition, HP improved mitochondrial function and reduced oxidative stress induced by OGD. It was found that HP astrocytes had a greater neuroprotective effect than normal astrocytes cells. Neuronal apoptosis and reactive oxygen species levels were down-regulated by cell co-culture. The PGC-1α siRNA experiment showed that hypoxia treatment promotes mitochondrial biogenesis and plays a neuroprotective role. HP significantly enhanced the efficacy of astrocytes in the treatment of neuronal injury.

A comparison of methods for yeast identification including CHROMagar Candida, Vitek system YBC and a traditional biochemical method

BACKGROUND

CHROMagar Candida (CAC) is a new chromogenic medium for the presumptive identification of clinically-important yeast isolates. A yeast biochemical card (YBC), a part of the Vitek system is an automatic method for the identification of clinically-important yeast isolates. We conducted a comparison of these two methods with a traditional biochemical method in order to choose a rapid and accurate technique for yeast identification.

METHODS

All yeast isolates were inoculated onto Sabourand dextrose agar (SDA) and CAC, and incubated at 30 degrees C for 48 hours. All isolates were simultaneously tested using traditional biochemical methods and the yeast biochemical card from the Vitek system.

RESULTS

We evaluated 235 yeast isolates from clinical specimens, including 89 Candida albicans, 47 Candida tropicalis, 43 Candida glabrata, six Trichosporon beigelii, and five Candida krusei in addition to 45 isolates of other yeast species. Isolates were presumptively identified on the basis of colony color and appearance on CAC medium. These observations were compared with a traditional biochemical yeast-identification method and also with YBC from the Vitek system. For five commonly-isolated species (Candida albicans, Candida tropicalis, Candida glabrata, Candida krusei and Trichosporon beigelii), agreement among the CAC medium, YBC method and traditional biochemical method were 98.9% (187/189), 96.3% (182/189), 100% (189/189), respectively.

CONCLUSIONS

From our comparison, the CAC medium is a convenient and economic method to identify five commonly-noted yeast species, and the YBC method warrants a greater cost and requires a longer period of time to obtain reliable results.

Presumptive identification of streptococci by pyrrolidonyl-beta-naphthylamide (PYR) test

BACKGROUND

Group A streptococci and enterococci can be differentiated from other streptococci on the basis of their ability to cleave L-pyrrolidonyl-beta-naphthylamide.

METHODS

In the present study, the L-pyrrolidonyl-beta-naphthylamide (PYR) test, pigment medium and bile esculin medium have been used to presumptively identify the streptococci. In total, 114 strains of group A streptococci, 350 strains of non-group A streptococci, 202 strains of enterococci and 197 strains of non-enterococci have been tested.

RESULTS

The results of the present investigation show that sensitivities of different test methods are: PYR broth, 99.08%; Murex PYR, 98.48%; bacitracin, 95%; bacitracin and sulfamethoxazole/trimethoprim (SXT), 95%; pigment medium, 99.23%; bile esculin medium, 99.26%. Additionally, specificities of various tests are: PYR broth and Murex PYR, 99.82%; bacitracin, 90.90%; bacitracin and SXT, 98.87%; pigment medium and bile esculin medium, 100%, respectively.

CONCLUSIONS

PYR test has been observed to be very easy to use and may hence be considered as a rapid, reliable and cost-effective method for presumptive identification of group A streptococci and enterococci in the clinical laboratory.

[Six semi-sold media methods for detecting motility of gram negative bacilli]

Motility is recognized as a significant biological character of certain bacteria, and is used as a fundamental basis of classification in many taxonomic systems. We compared wet mount method, semi-solid medium method and flagella stain method to evaluate the motility activity of 538 Enterobacteriaceae and 300 glucose non-fermentative gram negative bacilli. The results showed a sensitivity of 100% in flagella stain, Gilardi medium, Mueller Hinton semisolid medium and sulfide-indole-motility (SIM) medium (Difco); 99.6% in SIM (Kyokuto) and SIM (BBL); 99.3% in motility test medium (BBL) and 97% in wet mount. Motile Enterobacteriaceae grow well, and turbidity changes clearly and is easy to interpret. Motile glucose nonfermentative gram negative bacilli grow so lightly and rapidly diffuse throughout the medium and are hardly to interpret. It is better to use colorless Gilardi medium and Mueller Hinton semi-solid medium and to read within 4-8 hours or 24 hours. The advantages of the semi-solid medium method are particularly evident in teaching schedules and routine testing, because the results are cumulative, macroscopic, highly sensitive, and easy to manipulate.

[Comparison of the identification of Enterobacteriaceae by conventional method and computer analytical method]

The purpose of this study was to compare the effectiveness of identifying Enterobacteriaceae by either the conventional method or computer analytical method. The clinical isolates of 1124 species were examined by these two methods, and 1091 species had the same results. Thus the correspondence rate was 97.1%. The inconsistence of the conventional method was usually due to personal factors and the amount of the biochemical reagents. Using the computer analytical method, error due to personal reading could be eliminated. Computer analytical method is also more effective, economical, time-saving and higher in reproductability.

[Comparison of three pigment production media with CAMP and hippurate hydrolysis tests for the identification of beta-streptococcus group B]

Three pigment production media were compared with CAMP and hippurate hydrolysis tests for the identification of beta-Streptococcus group B. A total of 129 clinical isolates of beta-Streptococcus group B and 287 beta-Streptococcus non group B were tested. The results show that sensitivities are: pigment medium, 99.2%, DMS medium, 95.6%, Columbia agar, 92.8%, CAMP test, 96.3%, hippurate hydrolysis test, 97.6%. As for specificities results show: CAMP test, 99.7%, the other tests, 100%; respectively. Pigment medium is a simple, convenient methodology.