Persistent enhancement of bile acid synthesis in guinea pigs following stimulation of cholesterol catabolism in neonatal life

Cholesterol catabolism to bile acids was stimulated in neonatal guinea pigs by feeding 1,11% cholestyramine (CT)-containing diet for 8 weeks. The animals were then switched to standard laboratory diet for an additional 4 weeks. At the end of the laboratory diet period: a) CT-pre-treated guinea pigs continued to excrete significantly higher (p<0.05) amounts of bile acids, b) the activity of hepatic 7α-hydroxylase was significantly elevated (p<0.01) in CT-pre-treated animals, and c) isolated hepatocytes from CT-pre-treated guinea pigs secreted significantly higher (p<0.05) amounts of bile acid when compared to controls during a 4-hour incubation. These data provide biochemical support for our contention that stimulation of cholesterol catabolism during neonatal life can have effects that persist into adult life.     

Early effects of salinity on nitrate assimilation in barley seedlings

The effect of NaCl and Na₂SO₄ salinity on NO₃⁻ assimilation in young barley (Hordeum vulgare L. var Numar) seedlings was studied. The induction of the NO₃⁻ transporter was affected very little; the major effect of the salts was on its activity. Both Cl⁻ and SO₄²⁻ salts severely inhibited uptake of NO₃⁻. When compared on the basis of osmolality of the uptake solutions, Cl⁻ salts were more inhibitory (15-30%) than SO₄²⁻ salts. At equal concentrations, SO₄²⁻ salts inhibited NO₃⁻ uptake 30 to 40% more than did Cl⁻ salts. The absolute concentrations of each ion seemed more important as inhibitors of NO₃⁻ uptake than did the osmolality of the uptake solutions. Both K⁺ and Na⁺ salts inhibited NO₃⁻ uptake similarly; hence, the process seemed more sensitive to anionic salinity than to cationic salinity.

Unlike NO₃⁻ uptake, NO₃⁻ reduction was not affected by salinity in short-term studies (12 hours). The rate of reduction of endogenous NO₃⁻ in leaves of seedlings grown on NaCl for 8 days decreased only 25%. Nitrate reductase activity in the salt-treated leaves also decreased 20% but its activity, determined either in vitro or by the `anaerobic' in vivo assay, was always greater than the actual in situ rate of NO₃⁻ reduction. When salts were added to the assay medium, the in vitro enzymic activity was severely inhibited; whereas the anaerobic in vivo nitrate reductase activity was affected only slightly. These results indicate that in situ nitrate reductase activity is protected from salt injury. The susceptibility to injury of the NO₃⁻ transporter, rather than that of the NO₃⁻ reduction system, may be a critical factor to plant survival during salt stress.

     

Dependency of Nitrate Reduction on Soluble Carbohydrates in Primary Leaves of Barley under Aerobic Conditions

Nitrate reduction was studied as a function of carbohydrate concentration in detached primary leaves of barley (Hordeum vulgare L. cv Numar) seedlings under aerobic conditions in light and darkness. Seedlings were grown either in continuous light for 8 days or under a regimen of 16-hour light and 8-hour dark for 8 to 15 days. Leaves of 8-day-old seedlings grown in continuous light accumulated 4 times more carbohydrates than leaves of plants grown under a light and dark regimen. When detached leaves from these seedlings were supplied with NO₃⁻ in darkness, those with the higher levels of carbohydrates reduced a greater proportion of the NO₃⁻ that was taken up. In darkness, added glucose increased the percentage of NO₃⁻ reduced up to 2.6-fold depending on the endogenous carbohydrate status of the leaves. Both NO₃⁻ reduction and carbohydrate content of the leaves increased with age. Fructose and sucrose also increased NO₃⁻ reduction in darkness to the same extent as glucose. Krebs cycle intermediates, citrate and succinate, did not increase NO₃⁻ reduction, whereas malate slightly stimulated it in darkness.

In light, 73 to 90% of the NO₃⁻ taken up was reduced by the detached leaves; therefore, an exogenous supply of glucose had little additional effect on NO₃⁻ reduction. The results indicate that in darkness the rate of NO₃⁻ reduction in primary leaves of barley depends upon the availability of carbohydrates.

     

Characterization of antimicrobial resistance and seasonal prevalence of Escherichia coli O157:H7 recovered from commercial feedlots in Alberta,Canada

Aims: To characterize antimicrobial resistance (AMR) and determine the seasonal prevalence of Escherichia coli O157:H7 isolated from commercial feedlots. Methods and Results: Escherichia coli O157:H7 were isolated from faecal and oral samples collected at monthly intervals from three commercial feedlots over a 12‐month period. A total of 240 isolates were characterized using pulsed‐field gel electrophoresis (PFGE) technique. A subset of 205 isolates was analysed for AMR using Sensititre system and AMR genes (tet, sul and str) by PCR. Seven PFGE clusters (≥90% Dice similarity) were identified, and two clusters common to all three feedlots were recovered year‐round. The majority of isolates (60%) were susceptible to all antimicrobials and were closely related (P < 0.001), whereas isolates with unique AMR patterns were not related. The prevalences of AMR from feedlots A, B and C were 69%, 1% and 38%, respectively. Resistance to tetracycline (69%) and sulfisoxazole (68%) was more prevalent in feedlot A than other two feedlots. The presence of strA and strB genes was linked in the majority of isolates, and tet(A) and tet(B), and sul1 and sul2 genes were present individually. Escherichia coli O157:H7 were genetically diverse during summer and fall, and strains from winter and spring months were more closely related. Conclusions: Antimicrobial resistance was more common in E. coli O157:H7 obtained from two of the three commercial feedlots, and the phenotypic expression of resistance was correlated with the presence of resistant genes. A highly diverse E. coli O157:H7 population was found during summer and fall seasons. Significance and Impact of the Study: Information would help understanding the dynamics of AMR in E. coli O157:H7 from commercial feedlots.     

Salinity Stress in Wheat: Effects,Mechanisms and Management Strategies

Salinity stress is a major threat to global food production and its intensity is continuously increasing because of anthropogenic activities. Wheat is a staple food and a source of carbohydrates and calories for the majority of people across the globe. However, wheat productivity is adversely affected by salt stress, which is associated with a reduction in germination, growth, altered reproductive behavior and enzymatic activity, disrupted photosynthesis, hormonal imbalance, oxidative stress, and yield reductions. Thus, a better understanding of wheat (plant) behavior to salinity stress has essential implications to devise counter and alleviation measures to cope with salt stress. Different approaches including the selection of suitable cultivars, conventional breeding, and molecular techniques can be used for facing salt stress tolerance. However, these techniques are tedious, costly, and labor-intensive. Management practices are still helpful to improve the wheat performance under salinity stress. Use of arbuscular mycorrhizal fungi, plant growth-promoting rhizobacteria, and exogenous application of phytohormones, seed priming, and nutrient management are important tools to improve wheat performance under salinity stress. In this paper, we discussed the effect of salinity stress on the wheat crop, possible mechanisms to deal with salinity stress, and management options to improve wheat performance under salinity conditions.     

Facile synthesized NaGdF4:Yb,Er peanut-shaped,highly biocompatible,colloidal upconversion nanospheres

A facile method was used for the synthesis of peanut-shaped very emissive NaGdF₄:Yb, Er upconversion nanospheres (UCNSs) at lower temperatures with uniform size distribution. Crystallographic structure, phase purity, morphology, thermal robustness, biocompatibility, colloidal stability, surface chemistry, optical properties, and luminesce properties were explored by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), zeta potential, thermogravimetric/differential thermal analysis (TGA/DTA), Fourier-transform infrared (FTIR), ultraviolet (UV)-visible and photoluminescence spectroscopic tools. XRD pattern verified the construction of a single-phase, highly-crystalline NaGdF₄ phase with a hexagonal structure. Peanut-shaped morphology of the sample was obtained from SEM micrographs which were validated from high-resolution TEM images, to have an equatorial diameter of 170 to 200 nm and a length of 220 to 230 nm, with irregular size, monodispersed, porous structure, and rough surface of the particles. The positive zeta potential value exhibited good biocompatibility along with high colloidal stability as observed from the absorption spectrum. The prepared UCNSs revealed high dispersibility, irregular size peanut-shaped morphology, rough surface, good colloidal stability, and excellent biocompatibility in aqueous media. A hexagonal phase NaGdF₄ doped with ytterbium (Yb) and erbium (Er) UCNSs revealed the characteristics of highly dominant emissions located at 520–525, 538–550, and 659–668 nm corresponding to the ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2, and ⁴F_9/2 → ⁴I_15/2 transition of Er³⁺ ions, respectively, as a result of energy transfer from sensitizer Yb³⁺ ion to emitter Er³⁺ ion.     

Human colon tissue in organ culture: preservation of normal and neoplastic characteristics

Normal and neoplastic human colon tissue obtained at surgery was used to establish conditions for organ culture. Optimal conditions included an atmosphere of 5% CO₂ and 95% O₂; tissue partially submerged with mucosa at the gas interface; and serum-free medium with 1.5 mM Ca²⁺ and a number of growth supplements. Histological, histochemical, and immunohistochemical features that distinguish normal and neoplastic tissue were preserved over a 2-d period. With normal tissue, this included the presence of elongated crypts with small, densely packed cells at the crypt base and mucin-containing goblet cells in the upper portion. Ki67 staining, for proliferating cells, was confined to the lower third of the crypt, while expression of extracellular calcium-sensing receptor was seen in the upper third and surface epithelium. E-cadherin and β-catenin were expressed throughout the epithelium and confined to the cell surface. In tumor tissue, the same disorganized, abnormal glandular structures seen at time zero were present after 2 d. The majority of cells in these structures were mucin-poor, but occasional goblet cells were seen and mucin staining was present. Ki67 staining was seen throughout the abnormal epithelium and calcium-sensing receptor expression was weak and variable. E-cadherin was seen at the cell surface (similar to normal tissue), but in some places, there was diffuse cytoplasmic staining. Finally, intense cytoplasmic and nuclear β-catenin staining was observed in cultured neoplastic tissue.