Ruminal transport and metabolism of short-chain fatty acids (SCFA) in vitro: effect of SCFA chain length and pH

The unidirectional transport and metabolism of 14C-labeled acetate, propionate and butyrate across the isolated bovine rumen epithelium was measured in vitro by the Ussing chamber technique. There was a significant, but relatively small, net secretion of acetate and propionate, and a large and significant net absorption of butyrate. The results demonstrate that the mucosal-serosal (MS) pathway for short-chain fatty acids (SCFA) is different from the serosal-mucosal (SM) pathway, and that butyrate is treated differently from acetate and propionate by the epithelium. The results support that the main route for epithelial SCFA transport is transcellular. The correlation between SCFA lipophility and the flux rate was positive but weak at both pH 7.3 and 6.0. Decreasing pH increased all SCFA fluxes significantly, but not proportionally to the increase of protonized SCFA in the bathing solution. There was a significant and apparently non-competitive interaction between the transport of acetate, propionate and butyrate. It seems that mediated transport mechanisms must be involved in epithelial SCFA transport in the bovine rumen, but the data do not exclude that passive diffusion could account for a significant part of the flux. The metabolism of SCFA in the Ussing chamber system was considerable, and there was a clear preference for excretion of CO2 from this metabolism to the mucosal side, while side preference for non-CO2 metabolite excretion was not studied. Of the propionate and butyrate transported in the MS direction, 78 and 95% was metabolised, while only 37 and 38% was metabolised in the SM direction (acetate metabolism could not be measured). There was, however, no simple relation between the degree of metabolism and the transport rate or the transport asymmetry of the SCFA.     

Tumour necrosis factor-alpha interacts with biglycan and decorin

The interaction of beta-arrestin-1 with the somatostatin receptor type 2A (sst2A) was monitored using both biochemical and confocal imaging approaches. We show that, using transient transfection of either beta-arrestin-1 or its dominant negative Delta-arrestin-1 in CHO cells stably transfected with the sst2A, beta-arrestin-1 is colocalized with the receptor in endosomal vesicles after somatostatin-induced sequestration. However, this interaction leads to a role of beta-arrestin-1 in the desensitization of the sst2A rather than in the internalization process of the receptor-ligand complex.     

Structure and the energy of base pairing in non-natural bases of nucleic acids: the azaguanine-cytosine and azaadenine-thymine base pairs

Watson-Crick optimized geometries and the energies of base pairing for the natural pairs of nucleic bases: adenine-thymine (AT) and guanine-cytosine (GC) have been recalculated by ab initio methods in order to compare results to those found for the non-natural azaadenine-thymine (AAT) and azaguanine-cytosine (AGC) pairs. Geometry optimizations carried out at the HF/6-31G** level and energies obtained at MP2/6-31G**, show that AAT and AGC have hydrogen bonding patterns similar to the natural AT and GC and that the interaction energies (DeltaH0int) for the former are ca. 7 kcal/mol more stable than the latter. Accordingly, the pairs based on azapurines would be favored with respect to the natural pairs. Some possible explanations why nature does not use extensively the azabases in base pairing are given.     

Characterization of CIM monoliths as enzyme reactors

The immobilization of the enzymes citrate lyase, malate dehydrogenase, isocitrate dehydrogenase and lactate dehydrogenase to CIM monolithic supports was performed. The long-term stability, reproducibility, and linear response range of the immobilized enzyme reactors were investigated along with the determination of the kinetic behavior of the enzymes immobilized on the CIM monoliths. The Michaelis-Menten constant K(m) and the turnover number k(3) of the immobilized enzymes were found to be flow-unaffected. Furthermore, the K(m) values of the soluble and immobilized enzyme were found to be comparable. Both facts indicate the absence of a diffusional limitation in immobilized CIM enzyme reactors.     

Coevolutionary interactions between a haploid species and a diploid species

We investigate a general model describing coevolutionary interaction between a haploid population and a diploid population, each with two alleles at a single locus. Both species are allowed to evolve, with the fitness of the genotypes of each species assumed to depend linearly on the frequencies of the genotypes of the other species. We explore the resulting outcomes of these interactions, in particular determining the location of equilibria under various conditions. The coevolution here is much more complex than that between two haploid populations and allows for the possibility of two polymorphic equilibria. To allow for further analysis, we construct a semi-symmetric model. The variety of outcomes possible even in this second model provides support for the geographic mosaic theory of coevolution by suggesting the possibility of small local populations coevolving to very different outcomes, leading to a shifting geographic mosaic as neighboring populations interact with each other through migration.     

Antisense Oligonucleotide of Clusterin mRNA Induces Apoptotic Cell Death and Prevents Adhesion of Rat ASC-17D Sertoli Cells

Clusterin has been known to play important roles in cell-cell and/or cell-substratum interactions. Recently we reported the transient expression of clusterin in pancreatic endocrine cells during the early developmental stages and suggested a role in aggregating the endocrine cells for islet formation. In the present study, we have investigated the involvement of clusterin in cell-substratum interaction by the inhibition of clusterin synthesis using antisense oligonucleotide. The expression of clusterin was transiently increased as early as 2–8 h after plating the ASC-17D Sertoli cells to the culture flask, which was the period of cell attachment. In addition, up-regulation of clusterin mRNA was so much greater when the Sertoli cells were plated on the petri dish for the bacterial culture instead of in a animal cell culture flask that therefore, the cells failed to attach to it. These findings suggested that interruption of cell to plate substratum interaction might lead to over-expression of clusterin from Sertoli cells to induce cell to cell aggregation or, perhaps, to re-establish attachment with the substratum. Transfection of ASC-17D Sertoli cells with a 20-base antisense oligonucleotide against clusterin mRNA resulted in extracellular release of LDH and DNA fragmentation. Sertoli cell death by antisense oligonucleotide of clusterin was sequence specific and dose dependent. Treatment of antisense oligonucleotide induced a marked reduction of synthesis for clusterin protein, but not for clusterin mRNA expression, suggesting the translational suppression of clusterin by antisense oligonucleotide. Further, microscopic observation showed that more noticeable cell death was induced by treating the antisense prior to plating the cells than by treating after cell attachment to the plate. From these results, we speculate that down-regulation of clusterin expression in the anchorage-dependent Sertoli cells prevents them from attaching to the plate, and therefore induces cell death.     

Nickel-quinolones interaction. Part 2 - Interaction of nickel(II) with the antibacterial drug oxolinic acid

The mononuclear nickel(II) complexes with the first-generation quinolone antibacterial agent oxolinic acid in the presence or absence of nitrogen-donor heterocyclic ligands (2,2′-bipyridine, 1,10-phenanthroline or pyridine) have been synthesized and characterized. The experimental data suggest that oxolinic acid acts as deprotonated bidentate ligand coordinated to Ni(II) ion through the ketone and carboxylato oxygens. The crystal structure of (2,2′-bipyridine)bis(oxolinato) nickel(II), 2 has been determined by X-ray crystallography. The cyclic voltammograms of the complexes recorded in dmso solution and in 1/2 dmso/buffer (containing 150 mM NaCl and 15 mM trisodium citrate at pH 7.0) solution have shown that in the presence of calf-thymus DNA (CT DNA) they can bind to CT DNA by the intercalative binding mode. UV study of the interaction of the complexes with CT DNA has shown that the complexes bind to CT DNA and bis(aqua)bis(oxolinato) nickel(II) exhibits the highest binding constant to CT DNA. Competitive study with ethidium bromide (EB) has shown that the complexes can displace the DNA-bound EB indicating that they bind to DNA in strong competition with EB. The complexes exhibit good binding propensity to human or bovine serum albumin protein having relatively high binding constant values.     

CdTe quantum dots (QDs) improve the affinities of baicalein and genistein for human serum albumin in vitro

Baicalein and genistein were studied for the affinities for human serum albumin (HSA) in the presence and absence of three CdTe quantum dots (QDs) with different sizes. Three typical CdTe QDs with maximum emissions of 535 nm (green-emitting, G-QDs), 598 nm (yellow-emitting, Y-QDs), and 654 nm (red-emitting, R-QDs) were tested. The fluorescence intensities of HSA decreased remarkably with increasing concentration of QDs. Baicalein resulted in an obvious blue-shift of the λ_em of HSA from 340 to 334 nm. However, the extents of blue-shifts induced by baicalein and genistein in the presence of QDs were much bigger than that in the absence of QDs. The quenching process of baicalein for HSA was easily affected by the QDs size than that of genistein. QDs increased the quenching constant from 136.97% to 162.24% for baicalein. However, QDs only increased the quenching constants from 20.56% to 32.23% for genistein. G-QDs, Y-QDs, and R-QDs increased the affinities of baicalein for HSA about 3.02%, 6.38% and 9.40%. G-QDs, Y-QDs, and R-QDs increased the affinities of genistein for HSA about 2.56%, 13.46% and 19.44%. The binding affinities of baicalein and genistein for HSA increased with increasing QDs size.     

蓝细菌别藻蓝蛋白ApcE与ApcF不形成复合物

进行了Anabaena sp.PCC7120的别藻蓝蛋白ApcE与ApcF的体内重组的光谱和apcE和apcF基因的细菌双杂交的研究。在提纯前PCB-ApcE/PCB-ApcF的吸收及荧光光谱峰与PCB-ApcF的峰位置一致,而提纯后PCB-ApcE/PCB-ApcF的吸收及荧光光谱峰与PCB-ApcE的峰位置一致,表明ApcE与ApcF不能形成复合物。pBT-apcF与pTRG-apcE的转化细胞能在无3氨基-1,2,4三氮唑（3-AT）的非选择性培养基上生长,而不能在有3AT的选择性培养基上生长,说明在转化过程中未产生能抗3-AT的HIS3报告基因,进一步证实ApcE与ApcF间没有相互作用。