Differential regulation of the GLUT1 and GLUT3 glucose transporters by growth factors and pro-inflammatory cytokines in equine articular chondrocytes

Glucose serves as the major energy substrate for articular chondrocytes and as the main precursor for the synthesis of extracellular matrix glycosaminoglycans in cartilage. Chondrocytes have been shown to express several glucose transporter (GLUT) isoforms including GLUT1 and GLUT3. The aim of this investigation was to determine the effects of endocrine and cytokine factors on the capacity of equine articular chondrocytes for transporting 2-deoxy-d-[2,6-3H] glucose and on the expression levels of GLUT1 and GLUT3. Chondrocytes maintained in monolayer culture were stimulated for 24 h with TNF-alpha (100 ng mL(-1)), IL-1beta (100 ng mL(-1)), IGF-I (20 ng mL(-1)), TGF-beta (20 ng mL(-1)) and insulin (12.5 microg mL(-1)) before measuring uptake of non-metabolizable 2-deoxyglucose in the presence and absence of the glucose transport inhibitor cytochalasin B. Polyclonal antibodies to GLUT1 and GLUT were used to compare GLUT1 and GLUT3 expression in stimulated and un-stimulated alginate encapsulated chondrocytes by Western blotting. Results indicated that 2-deoxyglucose uptake was inhibited by up to 95% in the presence of cytochalasin B suggesting that glucose uptake into equine chondrocytes is GLUT-mediated. Insulin had no effect on glucose uptake, but treatment with IGF-I, TGF-beta, IL-1beta and TNF-alpha resulted in a significant increase (>65%) in 2-deoxyglucose uptake compared to control values. GLUT1 was found to be increased in chondrocytes stimulated with all the growth factors and cytokines but GLUT 3 was only upregulated by IGF-I. The data presented support a critical role for glucose in the responses of equine articular chondrocytes to pro-inflammatory cytokines and anabolic endocrine factors.     

Electron transfer-induced dynamics of oxygen molecules on the TiO2(110) surface

Diffusion of oxygen molecules on transition metal oxide surfaces plays a vital role for the understanding of catalysis and photocatalysis on these materials. By means of time-resolved scanning tunneling microscopy, we provide evidence for a charge transfer-induced diffusion mechanism for O2 molecules adsorbed on a rutile TiO2(110) surface. The O2 hopping rate depended on the number of surface donors (oxygen vacancies), which determines the density of conduction band electrons. These results may have implications for the understanding of oxidation processes on metal oxides in general.     

Soil-solution chemistry in a low-elevation spruce-fir ecosystem,Howland, Maine

Soil solutions were collected monthly by tension and zero-tension lysimeters in a low-elevation red spruce stand in east-central Maine from May 1987 through December 1992. Soil solutions collected by Oa tension lysimeters had higher concentrations of most constituents than the Oa zero-tension lysimeters. In Oa horizon soil solutions growing season concentrations for SO₄, Ca, and Mg averaged 57, 43, and 30 μmol L^?1 in tension lysimeters, and 43, 28, and 19 μmol L^?1 in zero-tension lysimeters, respectively. Because tension lysimeters remove water held by the soil at tensions up to 10 kPa, solutions are assumed to have more time to react with the soil compared to freely draining solutions collected by zero-tension lysimeters. Solutions collected in the Bs horizon by both types of collectors were similar which was attributed to the frequency of time periods when the water table was above the Bs lysimeters. Concentrations of SO₄ and NO₃ at this site were lower than concentrations reported for most other eastern U.S. spruce-fir sites, but base cation concentrations fell in the same range. Aluminum concentrations in this study were also lower than reported for other sites in the eastern U.S. and Ca/Al ratios did not suggest inhibition of Ca uptake by roots. Concentrations of SO₄, Ca, K, and Cl decreased significantly in both the Oa and Bs horizons over the 56-month sampling period, which could reflect decreasing deposition rates for sulfur and base cations, climatic influences, or natural variation. A longer record of measured fluxes will be needed to adequately define temporal trends in solution chemistry and their causes.     

A rapid aflatoxin B1 ELISA: development and validation with reduced matrix effects for peanuts, corn, pistachio, and Soybeans

Among the competitive ELISAs for aflatoxins that have been described, few have been adequately validated for reduced matrix effects. Using an aflatoxin B(1) (AFB(1))-specific polyclonal antibody (produced from AFB(1)-oxime conjugated to bovine serum albumin (BSA)) and AFB(1)- and AFB(2)-enzyme conjugates, four direct competitive ELISAs based on 96-microwell plates (two standard assays and two rapid assays) were developed, paying special attention to producing a robust assay relatively free of interferences for a range of agricultural products. The antibody was AFB(1)-specific, detecting only AFB(1) in a mixture of four aflatoxins (AFB(1), AFB(2), AFG(1), and AFG(2)), but showed significant cross-reaction with AFG(1) (57-61%) when an individual compound was tested. Standard assays (long assays) exhibited higher sensitivities than rapid assays (short assays) with IC(50) values of 12 +/- 1.5 and 9 +/- 1.5 microg/kg in sample (with 1 in 5 dilution of sample extract) for AFB(1) and AFB(2)-enzyme conjugates, respectively. These assays have narrower detection ranges (7.1-55.5 microg/kg in sample) and required dilution of sample extracts to overcome solvent and matrix interferences, making these assays less ideal as analytical methods. Rapid assays exhibited IC(50) values of 21.6 +/- 2.7 and 12 microg/kg in sample for AFB(1)- and AFB(2)-enzyme conjugates, respectively. These assays have ideally broader detection ranges (4.2-99.9 microg/kg in sample) and showed no methanol effects up to 80% with significantly reduced matrix interferences as a result of the shorter incubation times and increasing the amounts of enzyme conjugate used. Therefore, the rapid assays were formatted to perform without a need for extract dilution. The rapid assays can be completed within 15 min, potentially suitable for receival bays where quick decision-making to segregate low and high contamination is critical. Further validation using the rapid assay with AFB(1)-enzyme conjugate indicated relatively good recoveries of AFB(1) spiked in corn, peanuts, pistachio, and soybeans, which were free from significant matrix effects. It can be concluded that this rapid assay would be suitable for monitoring aflatoxin AFB(1) at current legal maximum residue limits of 10 microg/kg in food such as corn, peanuts, pistachio, and soybeans.     

Aroma Compounds in Buckwheat (Fagopyrum esculentum Moench) Groats,Flour, Bran,and Husk

Buckwheat is a pseudocereal with a strong characteristic aroma. Compounds responsible for the aroma of buckwheat groats were recently identified, but the distribution of aromatic compounds between different fractions of the buckwheat kernel (flour, bran, and husk) is not yet known. In this study, the composition of aromatic compounds in buckwheat seed fractions was investigated and compared to the composition of aromatic compounds in groats produced from the same batch of buckwheat seeds. Volatiles from each sample were extracted with simultaneous distillation/extraction with a Likens‐Nickerson apparatus. Extracts were analyzed by gas chromatography coupled with mass spectrometry (GC‐MS) with electron ionization. Apart from the aroma molecules present in all fractions, compounds that are present only in flour or bran, but not in groats, were also found. Furthermore, some compounds were identified only in buckwheat groats but not in buckwheat flour or bran [octanal, (E,E)‐2,4‐heptadienal, (E)‐2‐decenal, and (E,E)‐2,4‐decadienal], others were identified only in husks [(E)‐2‐hexenal, heptanal, (E,E)‐2,4‐hexadienal, phenylacetaldehyde, and alpha‐bisabolol].     

Rapid quantification of humic components in concentrated humate fertilizer solutions by FTIR spectroscopy

Journal of Soils and Sediments - The use of humic substances is under thorough discussion of state-of-the-art agricultural science. They are marketed mostly as concentrated aqueous solutions of...     

Testcross performance and diversity analysis of white maize lines derived from backcrosses containing exotic germplasm

Introgression from exotic maize (Zea mays L.) into adapted breeding pools can broaden and diversify the genetic base of adapted germplasm. The first objective of this study was to determine the agronomic performance of white maize lines derived from adapted × exotic backcrosses in tropical environments. Six exotic white maize inbred lines were crossed to an adapted white line (1368) and the F₁s were backcrossed to 1368. Forty-one BC₁F₄ lines derived from these backcrosses and the recurrent parent were crossed with a common inbred tester (9071) and the progeny were evaluated at eight environments in Nigeria. The testcrosses × environment interaction mean square was not significant for all agronomic traits. The BC-derived lines containing exotic germplasm contributed significantly to the variation in testcross mean grain yields and other agronomic traits. Among the 41 testcrosses, only 5 yielded significantly less than 1368 × 9071, with the 7 best testcrosses producing between 304 and 867 kg ha⁻¹ more grain than 1368 × 9071. The second objective of this study was to assess the genetic divergence of the BC-derived white lines from their adapted recurrent parent. Thirty-nine BC-derived white lines along with 1368 and 9071 were genotyped with ten AFLP primer pairs that generated 506 polymorphic fragments. The average allelic diversity of the lines was 31 ± 0.07. The genetic distance (GD) estimates of each BC-derived line from 1368 varied from 0.76 to 0.84, with a mean of 0.80 ± 0.003. The average GD for all pairs of the BC-derived lines was 0.63 ± 0.005, varying from 0.31 to 0.89. The observed significant amount of variation among the BC-derived white lines suggests that they can contribute new alleles for expanding the genetic base of tropical maize and for developing high-yielding hybrids.