Exopolysaccharide production by Lactobacillus delbruckii subsp. bulgaricus and Streptococcus thermophilus strains under different growth conditions

Summary The optimal temperature, pH and incubation time for production of exopolysaccharide (EPS) by Lactobacillus delbruckii subsp. bulgaricus and Streptococcus thermophilus strains in MRS and M17 media, respectively, were determined. In all strains, the temperature and incubation time for EPS production were 45 °C and 18 h, respectively. At 45 °C, L. delbruckiisubsp. bulgaricus B3 and G12 and S. thermophilus W22 strains produced 263, 238 and 127 mg/l, respectively. At 18 h, B3, G12 and W22 strains produced 220, 152 and 120 mg/l, respectively. While the pH for highest EPS production by L. delbruckii subsp. bulgaricus strains was 6.2 (in B3 strain: 211 mg/l, in G12 strain: 175 mg/l), for highest EPS production byS. thermophilus strain it was 6.8 (114 mg/l).     

Treatment with AT(1) receptor blocker restores diabetes-induced alterations in intracellular Ca(2+) transients and contractile function of rat myocardium

We investigated the effect of treatment with an angiotensin II receptor blocker, candesartan-cilexetil, on the mechanical and electrophysiological properties of cardiomyocytes isolated from streptozotocin-induced diabetic (STZ) rats. Contractile activity and electrophysiological properties were measured in papillary muscle and ventricular cardiomyocytes from normoglycemic and STZ-induced diabetic rats given vehicle or 5mg/kg/day candesartan-cilexetil for 4 weeks. Alterations in the kinetics of contractile activity and intracellular Ca(2+) transients were observed as well as a typical prolongation of action potential duration and significant decrease of potassium currents in diabetic rat heart preparations. Candesartan-cilexetil treatment recovered significantly prolonged action potential and depressed potassium currents in diabetic rats. It was also shown that treatment with AT(1) blocker restored altered kinetics of both the Ca(2+) transients in cardiomyocytes and the contractile activity in papillary muscle strips of diabetic rats. We also showed that incubation of cardiomyocytes from diabetic rats with a protein kinase C (PKC) inhibitor bisindolylmaleimide I (BIM) had a similar effect to candesartan treatment on the Ca(2+) transients. Thus, angiotensin II receptor blockade protects the heart from the development of cellular alterations typically related with diabetes, and this action of AT(1) receptors seems to be related with the activity of PKC.     

Functional requirements for signaling through the stimulatory and inhibitory mouse NKR-P1 (CD161) NK cell receptors

The NK cell receptor protein 1 (NKR-P1) (CD161) molecules represent a family of type II transmembrane C-type lectin-like receptors expressed predominantly by NK cells. Despite sharing a common NK1.1 epitope, the mouse NKR-P1B and NKR-P1C receptors possess opposing functions in NK cell signaling. Engagement of NKR-P1C stimulates cytotoxicity of target cells, Ca2+ flux, phosphatidylinositol turnover, kinase activity, and cytokine production. In contrast, NKR-P1B engagement inhibits NK cell cytotoxicity. Nonetheless, it remains unclear how different signaling outcomes are mediated at the molecular level. Here, we demonstrate that both NKR-P1B and NKR-P1C associate with the tyrosine kinase, p56(lck). The interaction is mediated through the di-cysteine CxCP motif in the cytoplasmic domains of NKR-P1B/C. Disrupting this motif leads to abrogation of both stimulatory and inhibitory NKR-P1 signals. In addition, mutation of the consensus ITIM (LxYxxL) in NKR-P1B abolishes both its Src homology 2-containing protein tyrosine phosphatase-1 recruitment and inhibitory function. Strikingly, engagement of NKR-P1C on NK cells obtained from Lck-deficient mice failed to induce NK cytotoxicity. These results reveal a role for Lck in the initiation of NKR-P1 signals, and demonstrate a requirement for the ITIM in NKR-P1-mediated inhibition.     

In vitro inhibition effects on erythrocyte carbonic anhydrase I and II and structure-activity relationships of cumarylthiazole derivatives

Coumarin and heterocyclic compounds incorporating urea have clinical applications as antiepileptics, diuretics, and antiglaucoma agents due to their carbonic anhydrase inhibitory properties. We investigated inhibition of carbonic anhydrase I and II with a series of coumarylthiazole derivatives containing urea/thiourea groups. All the investigated compounds exhibited inhibitory activity on both hCA I and hCA II, with 1-(3-chlorophenyl)-3-(4-(2-oxo-2H-chromen-3-yl)thiazol-2-yl)urea being the strongest inhibitor. Structure–activity relationship study showed that most of urea derivatives were more inhibiting for hCA I and hCA II than thiourea derivatives. The electron-withdrawing groups at the phenyl ring increased the inhibitory activity compared to electron-donating groups.     

The effect of selenium and vitamin E on microvascular permeability of rat organs

The effects of dietary sodium selenite and vitamin E on the microvascular permeability of rat organs such as heart, brain, kidney, liver and eye were investigated by using the Evans blue leakage method. Combined deficiency of selenium and vitamin E caused an increase in the permeability of the heart and eye with respect to their controls while it had no considerable effect on the permeability of other organs. On the other hand, toxic levels of selenium (4.2 mg/kg) in diet decreased the permeabilities in kidney, liver, and eye whereas this parameter of brain increased in the same animal group. These results suggested that low or high sodium selenite and vitamin E contents in diet could alter the microvascular permeability of different organs in different manners. It might be important to give reasonable explanations for the pathophysiology of some diseases that are characterized with organ damage and /or disfunction originated from selenium deficiency or toxicity.     

Identification of <Emphasis Type="Italic">Lactobacillus</Emphasis> strains from breast-fed infant and investigation of their cholesterol-reducing effects

Hypercholesterolemia has been reported to be the main cause of cardiovascular diseases and the leading cause of death. Therefore, decreasing serum cholesterol level is very important for preventing the cardiovascular diseases. It has been supposed that probiotics in human gastrointestinal tract have the ability to decrease serum cholesterol level by reducing the absorption of cholesterol from the intestinal tract and the bile salt deconjugation. In this study, 28 strains of Lactobacillus spp., isolated from breast-fed infant’s feces, were identified and investigated for their bile salt deconjugation ability. The deconjugation ability of the strains was determined by the release of cholic acid resulting from the deconjugation of conjugated bile salts. Research results showed that four of the strains had bile salt deconjugation ability. The strains with deconjugation ability have been identified in species level by using biochemical test, and molecular techniques, API 50CHL test and 16S rRNA gene sequence analysis respectively. LP1, E3, and E9 strains with deconjugation activity were identified as Lactobacillus rhamnosus and GD2 strain as Lactobacillus plantarum. Even if oxgall decreases the viability of bacteria, the highest amount of cholesterol precipitation (42%) was performed by GD2 strain in the presence of 0.3% (w/v) bile. This study demonstrated that the identified Lactobacillus strains had an excellent ability to survive at low pH, a high bile deconjugation ability, and hypocholesterolemic effect in in vitro conditions.