Close association between intestinal microbiota and irritable bowel syndrome.

Trillions of microbes inhabiting the intestine form a complex ecological community, affecting the normal physiology and pathological susceptibility through their collective metabolic activities and interactions with the host. Increased numbers of diseases have been found to be associated with disturbances in this ecosystem. There is evidence that intestinal microflora undergoes alterations in patients with irritable bowel syndrome (IBS). IBS is a frequent functional gut disease with negative impact on the patient's quality of life. Although the etiology and pathology of IBS remain largely unknown, it is generally accepted that the interaction between the microbiota and the host is associated with IBS. However, there are no specific or effective therapies for the treatment of IBS at present. In recent years, researchers have shown a growing interest in seeking safer and more effective alternatives for the treatment of IBS by focusing their attention on the potential role of probiotics and prebiotics. In this review, we will discuss alterations in intestinal microbiota and how these alterations may exacerbate IBS, and introduce several new IBS treatment options aiming at re-establishing a healthy and beneficial ecosystem.

Performance of the matrix-assisted laser desorption ionization time-of-flight mass spectrometry system for rapid identification of streptococci: a review.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been developed as a new type of soft ionization mass spectrometry in recent years. An increasing number of clinical microbiological laboratories consider it as an innovative approach for bacterial identification. This study was undertaken in order to evaluate the use of MALDI-TOF MS for rapid identification of the clinical streptococci. A systematic review was conducted based on a literature search of the Medline and Embase databases. Fixed-effects models based on the P-value and the I-square were used for meta-analysis while considering the possibility of heterogeneity between studies. Statistical analyses were performed by using STATA 11.0. Twenty-seven studies covering 3,540 streptococci were included in our meta-analysis. The MALDI-TOF MS correctly identified the species of 96% (I2 = 92.8, P < 0.1) of the streptococci. The MALDI-TOF MS correctly identified the species of 99% of the Streptococcus pneumoniae (I2 = 85.2%, P < 0.1), 100% of the Streptococcus pyogenes (I2 = 32.8%, P > 0.1), and 100% of Streptococcus agalactiae (I2 = 20.7%, P > 0.2). What's more, it also had high confidence in other Streptococcus. But the accuracy of bovis needs to be improved. The overall performance of both MALDI-MS systems was different. Notably, the identifying accuracy rate of streptococci by VITEK MS was 98%, compared to 94% by the MALDI biotyper system. Interestingly, when analyzing the incorrect identification of MALDI-TOF MS, 36 out of the 38 strains of Streptococcus mitis/oralis were inaccurately identified as Streptococcus pneumoniae by the MALDI biotyper system. In conclusion, the results of this review indicated that MALDI-TOF MS could be a reliable and rapid method for identification of the streptococci.

Protective effect of the new prepared Atractylodes macrocephala Koidz polysaccharide on fatty liver hemorrhagic syndrome in laying hens.

Fatty liver hemorrhage syndrome (FLHS) is the most common noninfectious cause of death in backyard chickens worldwide, which can cause a sudden drop in egg production in the affected flocks and cause huge losses to the laying hens breeding industry. In this study, we prepared polysaccharide from Atractylodes macrocephala Koidz (PAMK) by one-step alcohol precipitation. The structural analysis found that PAMK with a molecular weight of 2.816 × 103 Da was composed of glucose and mannose, in a molar ratio of 0.582 to 0.418. Furthermore, we investigated the hepatoprotective effects of PAMK on high-energy and low-protein (HELP) diet-induced FLHS in laying hens. The results showed that the hens' livers of the HELP diet showed yellowish-brown, greasy, and soft, whereas the supplement of PAMK (200 mg/kg or 400 mg/kg) could alleviate such pathological changes. The liver index, the abdominal fat percentage, and liver injury induced by the HELP diet were reduced in PAMK (200 mg/kg or 400 mg/kg). Supplementing 200 mg/kg or 400 mg/kg PAMK showed improvements of the antioxidant capacity in laying hens. Furthermore, we found that the HELP diet increased the expression of hepatic lipogenesis genes and decreased the expression of fatty acid ß-oxidation genes, which could be reversed by 200 mg/kg or 400 mg/kg PAMK supplementation. Nevertheless, there is no difference between the addition of 40 mg/kg PAMK and the HELP group. Collectively, these results showed that PAMK supplements could ameliorate HELP diet-induced liver injury through regulating activities of antioxidant enzymes and hepatic lipid metabolism. Therefore, PAMK could be a potential feedstuff additive to alleviate FLHS in laying hens.

The exchange factor Ras-GRF2 activates Ras-dependent and Rac-dependent mitogen-activated protein kinase pathways.

Ras and Rac are membrane-associated GTPases that function as molecular switches activating intracellular mitogen-activated protein kinase (MAPK) cascades and other effector pathways in response to extracellular signals [1]. Activation of Ras and Rac into their GTP-bound conformations is directly controlled by specific guanine-nucleotide exchange factors (GEFs), which catalyze GDP release. Several Ras-specific GEFs that are related to the budding yeast protein Cdc25p have been described, whereas GEFs for Rac-related GTPases contain a region that is homologous to the oncoprotein DbI [2-3]. The Ras-GRF1 and Ras-GRF2 proteins, which couple Ras activation to serpentine receptors and calcium signals, contain both Cdc25 and DbI homology (DH) regions [3-4]. Here, we demonstrate that Ras-GRF2 is a bifunctional signaling protein that is able to bind and activate Ras and Rac, and thereby coordinate the activation of the extracellular-signal-regulated kinase (ERK) and stress-activated protein kinase (SAPK) pathways.

Cloning and characterization of Ras-GRF2, a novel guanine nucleotide exchange factor for Ras.

Conversion of Ras proteins into an activated GTP-bound state able to bind effector proteins is catalyzed by specific guanine nucleotide exchange factors in response to a large number of extracellular stimuli. Here we report the isolation of mouse cDNAs encoding Ras-GRF2, a multidomain 135-kDa protein containing a COOH-terminal Cdc25-related domain that stimulates release of GDP from Ras but not other GTPases in vitro. Ras-GRF2 bound specifically to immobilized Ras lacking bound nucleotides, suggesting stabilization of the nucleotide-free form of Ras as a mechanism of catalyzing nucleotide exchange. The NH2-terminal region of Ras-GRF2 is predicted to contain features common to various signaling proteins including two pleckstrin homology domains and a Dbl homology region. Ras-GRF2 also contains an IQ motif which was required for its apparent constitutive association with calmodulin in epithelial cells ectopically expressing Ras-GRF2. Transient expression of Ras-GRF2 in kidney epithelial cells stimulated GTP binding by Ras and potentiated calcium ionophore-induced activation of mitogen-activated protein kinase (ERK1) dependent upon the IQ motif. Calcium influx caused Ras-GRF2 subcellular localization to change from cytosolic to peripheral, suggesting a possible mechanism for controlling Ras-GRF2 interactions with Ras at the plasma membrane. Epithelial cells overexpressing Ras-GRF2 are morphologically transformed and grow in a disorganized manner with minimal intercellular contacts. Northern analysis indicated a 9-kb GRF2 transcript in brain and lung, where p135 Ras-GRF2 is known to be expressed, and RNAs of 12 kb and 2.2 kb were detected in several tissues. Thus, Ras-GRF2 proteins with different domain structures may be widely expressed and couple diverse extracellular signals to Ras activation.

Calmodulin-independent coordination of Ras and extracellular signal-regulated kinase activation by Ras-GRF2.

Ras-GRF2 (GRF2) is a widely expressed, calcium-activated regulator of the small-type GTPases Ras and Rac. It is a multidomain protein composed of several recognizable sequence motifs in the following order (NH(2) to COOH): pleckstrin homology (PH), coiled-coil, ilimaquinone (IQ), Dbl homology (DH), PH, REM (Ras exchanger motif), PEST/destruction box, Cdc25. The DH and Cdc25 domains possess guanine nucleotide exchange factor (GEF) activity and interact with Rac and Ras, respectively. The REM-Cdc25 region was found to be sufficient for maximal activation of Ras in vitro and in vivo caused Ras and extracellular signal-regulated kinase (ERK) activation independent of calcium signals, suggesting that, at least when expressed ectopically, it contains all of the determinants required to access and activate Ras signaling. Additional mutational analysis of GRF2 indicated that the carboxyl PH domain imparts a modest inhibitory effect on Ras GEF activity and probably normally participates in intermolecular interactions. A variant of GRF2 missing the Cdc25 domain did not activate Ras and functions as an inhibitor of wild-type GRF2, presumably by competing for interactions with molecules other than calmodulin, Ras, and ligands of the PH domain. The binding of calmodulin was found to require several amino-terminal domains of GRF2 in addition to the IQ sequence, and no correlation between calmodulin binding by GRF2 and its ability to directly activate Ras and indirectly stimulate the mitogen-activated protein (MAP) kinase ERK in response to calcium was found. The precise role of the GRF2-calmodulin association, therefore, remains to be determined. A GRF2 mutant missing the IQ sequence was competent for Ras activation but failed to couple this to stimulation of the ERK pathway. This demonstrates that Ras-GTP formation is not sufficient for MAP kinase signaling. We conclude that in addition to directly activating Ras, GRF2, and likely other GEFs, promote the assembly of a protein network able to couple the GTPase with particular effectors.