青藏高原5种牧草木质素含量及其体外消化率研究

在海拔高度3200m的中国科学院海北高寒草甸生态系统定位站选取羊茅 Festucaovina 、早熟禾 Poaannua 、艹洽草 Koeoeriacristata 以及莎草科的矮嵩草 Kobresiahumilis 、黑褐苔草 Carexalrofusca 5种青藏高原重要牧草品种,分别测定羊茅、早熟禾、艹洽草、矮嵩草茎、矮嵩草叶、黑褐苔草茎和黑褐苔草叶的木质素含量,并采用二级离体培养法测定其体外消化率,比较不同牧草间木质素含量及消化率差异.1999和2000年两年的实验结果表明,牧草木质素含量与其体外消化率之间为极显著负相关 P<0.01 ;就同种牧草不同器官而言,牧草茎的木质素含量明显高于叶,其降解率较低;3种禾本科牧草及2种莎草科牧草不同牧草品种间木质素含量和体外消化率差异不显著.     

Carbohydrate content of bovine collagen preparations

Collagen preparations from bovine tissues were analysed for their carbohydrate content. Crude preparations of tropocollagen and polymeric collagen were found to be contaminated with considerable amounts of mannose, fucose and hexosamine, sugars known to be present in the mucoprotein of the interfibrillar material with which collagen is associated in vivo. A pure preparation of tropocollagen obtained by ethanol precipitation procedures contained only galactose and glucose in the approximate ratio of 7:3 residues/3000 amino acid residues. Purification of crude polymeric collagen by EDTA extraction or by crude bacterial amylase extraction considerably decreased the mucoprotein contamination, particularly in the enzymic treatment, which yielded a preparation containing predominantly galactose and glucose in the ratio of 4:2 residues/3000 amino acid residues. The results confirm previous work that demonstrated the purity of these collagen preparations as inferred by amino acid analysis. The results also indicate the suitability of the pure tropocollagen and the amylase-extracted polymeric collagen for studies on the role of the carbohydrate residues in intramolecular and intermolecular cross-linking in collagen.     

Transepithelial transport of ferulic acid by monocarboxylic acid transporter in Caco-2 cell monolayers

Our previous study (Biosci. Biotechnol. Biochem., 66, 2449-2457 (2002)), suggested that ferulic acid was transported via a monocarboxylic acid transporter (MCT). Transepithelial transport of ferulic acid was examined in this study by directly measuring the rate of its transport across Caco-2 cell monolayers. Ferulic acid transport was dependent on pH, and in a vectorical way in the apical-basolateral direction. The permeation of ferulic acid was concentration-dependent and saturable; the Michaelis constant was 16.2 mM and the maximum velocity was 220.4 nmol min-1 (mg protein)-1. Various substrates for MCTs, such as benzoic acid and acetic acid, strongly inhibited the permeation of ferulic acid, demonstrating that ferulic acid is obviously transported by MCT. Antioxidative phenolic acid compounds from dietary sources like ferulic acid would be recognized and transported by MCT by intestinal absorption.     

Reduction of the nucleic acid content of single-cell protein concentrates

Methods for reducing the content of nucleic acid in protein concentrates from disintegrated yeast and microalgae were investigated. Protein concentrates were prepared by acid precipitation of extracted protein after cell wall separation. The influence of alkaline protein extraction on the content of RNA in isoelectrically precipitated protein concentrates was studied. It was found that when a strong decrease in the RNA content was obtained, this was followed by a decrease in the yield of protein concentrate. Protein concentrates were also prepared without cell wall separation by precipitation with different agents after cell disintegration. In the precipitates from microalgae, a RNA reduction was obtained. Precipitation of yeast, protein gave no essential reduction with the precipitants used. Precipitation of yeast protein by heating at an alkaline pH gave a protein concentrate with a low content of RNA. A slightly lower RNA content was obtained when the precipitation was performed in the presence of NaCl. The yield of amino acid nitrogen was 70–80% and the RNA content was 1–2%. A process with precipitation at alkaline pH for the production of microbial protein concentrates with a low content of nucleic acid is suggested.     

Role of monocarboxylic acid transport in intracellular pH regulation of isolated proximal cells

Isolated proximal cells were prepared from rabbit kidney cortex by mechanical dissociation. The intracytoplasmic pH (pHi) was measured in HCO3(-)-free media (external pH (pHe), 7.3) using the fluorescent dye 2,7-biscarboxyethyl-5,6-carboxyfluorescein (BCECF). Cells were acid-loaded by the nigericin technique. Addition of 70 mM Na+ to the cells caused a rapid pHi recovery, which was blocked by 0.5 mM amiloride. When the cells were exposed to 5 mM sodium butyrate in the presence of 1 mM amiloride, the H+ efflux was significantly increased and followed Michaelis-Menten kinetics. Increasing pHe from 6.4 to 7.6 at a constant pHi of 6.4 enhanced the butyrate activation of the H+ efflux. Increasing pHi from 6.5 to 7.2 at a constant pHe of 7.2 reduced the butyrate effect. 22Na uptake experiments in the presence of 1 mM amiloride showed that 1.5 mM butyrate increased the Na+ flux in the proximal cells (pHi 7.10). The efficiency of monocarboxylic anions in promoting a pHi recovery increased with the length of their straight chain (acetate less than propionate less than butyrate less than valerate). The data show that when the Na+/H+ antiporter is blocked, the proximal cells can regulate their pHi by a Na+-coupled absorption of butyrate followed by non-ionic diffusion of butyric acid out of the cell and probably also by OH- influx by means of the OH-/anion exchanger.     

Phagocytic activity and protein content of human monocytes cultivated in the presence of various homologous interferon preparations

We have studied the effect of different types of interferons (IFN) on phagocytic activity and protein content when present during in vitro cultivation of human blood monocytes. Recombinant IFN-alpha and partially and highly purified leukocyte IFN preparations blocked the increase in phagocytic activity and protein content that occurs during in vitro cultivation of human monocytes. Fibroblast IFN blocked the increase in protein content, but did not significantly alter the phagocytic activity. IFN-gamma slightly enhanced phagocytic activity and protein content, while lymphoblastoid IFN preparations had no effect. The phagocytic activity and protein content of monocytes matured in vitro without IFN and then treated with IFN for 24 h was also tested. Phagocytosis via the non-specific receptors and the protein content was reduced by treatment of these cells with the IFN-alpha preparations. On the other hand Fc-receptor mediated phagocytosis was stimulated by IFN-gamma. Our data indicate that IFN effects on monocytes in culture varies depending on type and possibly subtypes of IFNs, and also on the timing of the treatment.     

Role of protein degradation in the regulation of cellular protein content and amino acid pools

A decrease in the rate of protein degradation contributes to the accumulation of cellular protein during growth or storage of dietary amino acids. Examples of this process in the liver of live mice are reviewed. One aspect of this regulation is the direct effect of amino acids on the rate of protein breakdown. At least in the case of histidine starvation in Chinese hamster ovary cells, the regulatory mechanism recognizes the level of aminoacylation of tRNA.     

Effect of alpha-lipoic acid preparations on bilirubin and transferrin levels and ferritin iron and transferrin iron content

The influence of ethylendiamine salt of alpha-lipoic acid on the indices of iron metabolism in patients with occupational pathologies has been studied using quantitative electron spin resonance spectroscopy. In the cases of treatment in the patients suffering from hyperferremia the decrease in transferrin iron concentration in the whole blood and plasma occurs correlating with the enhancement of iron excretion from urine and decline of bilirubin level in serum. We have found that the preparation chelates iron from iron (III)-citrate complex and form stable iron (III) complexes. The conclusion is that the positive effects of lipoic acid preparation in the patients with hyperferremia at least partially could be associated with normalization of iron exchange and reduction in the labile iron pool.     

Biological decomposition of fulvic acid preparations

Decomposition of preparations of various fractions of fulvio acids in pure cultures of bacteria and in the soil was investigated. In the soils enriched with fulvic acids the amount of bacteria increased, oxygen consumption and formation of carbon dioxide followed a typical sigmoid curve. The above measurements indicated that mineralization occurred after a very short or negligible lag phase. During the decomposition of fulvic acids the ability of microorganisms to oxidize aromatic compounds,e.g. vanillio andphydroxybenzoic acid, increased. The presence of aromatic structures in the used preparations of fulvic acids was demonstrated on the basis of their IR spectra and according to the results of Chromatographic analyses of their hydrolysates. The results indicated a relationship between metabolism offulvio acids and aromatic oompounds. In samples of the soil preincubated with glucose the fulvic acids decomposed more rapidly than in untreated samples.     

Non-involvement of the human monocarboxylic acid transporter 1 (MCT1) in the transport of phenolic acid

Phenolic acids such as p-coumaric acid and microbial metabolites of poorly absorbed polyphenols are absorbed by the monocarboxylic acid transporter (MCT)-mediated transport system which is identical to the fluorescein/H(+) cotransport system. We focus here on the physiological impact of MCT-mediated absorption and distribution. We examined whether MCT1, the best-characterized isoform found in almost all tissues, is involved in this MCT-mediated transport system. The induction of MCT1 expression in Caco-2 cells by a treatment with sodium butyrate (NaBut) did not increase the fluorescein permeability. Moreover, the transfection of Caco-2 cells with an expression vector encoding MCT1 caused no increase in either the permeability or uptake of fluorescein. Furthermore, in the MCT1-expressing oocytes, no increase of p-coumaric acid uptake was apparent, whereas the uptake of salicylic acid, a substrate of MCT1, nearly doubled. Our data therefore establish that MCT1 was not involved in the MCT-mediated transport of phenolic acids.     

单羧酸类Cl-通道阻断剂对心室肌CFTR Cl-通道的影响

本文采用全细胞膜片箝与细胞内灌注技术,观察了单羧酸类Ｃｌ＾－通道阻断剂对豚鼠心室肌囊性纤维变性膜透性调节蛋白（ＣＦＴＲ）Ｃｌ＾－电流的影响,细胞包９－ＡＣ以可逆方式增强异丙肾上腺素（ＩＳＯ）激发的ＣＦＴＲＣｌ＾－的外向电流成分,５－ｎｉｔｒｏ－２－（３－ｐｈｅｎｙｌｐｒｏｐｙｌａｍｉｎｏ）－ｂｅｎｚｏａｔｅ（ＮＰＰＢ）和二苯胺羧酸（ＤＰＣ）对ＩＳＯ发的ＣＦＴＲＣｌ＾－电流的作用呈现先增强后抑制的双     

Amino acid incorporation into the protein of mitochondrial preparations from cerebral cortex and spinal cord

1. Washed guinea-pig cerebral-cortex mitochondria incorporate [(14)C]leucine into their protein at a rate comparable with the rates reported for liver or heart mitochondria only if the mitochondria are separated from myelin and nerve endings by density-gradient centrifugation. 2. The non-mitochondrial components (myelin and nerve endings) of brain mitochondrial preparations incorporated [(14)C]leucine at a negligible rate. 3. The mitochondria do not require an exogenous supply of energy or a full supply of amino acids to support the process. 4. The incorporation rate was linear up to 2hr. aerobic incubation at 30 degrees and was inhibited by chloramphenicol, only slightly by actinomycin D and not by penicillin or pretreatment with ribonuclease. The observed incorporation is considered to be unlikely to be due to contaminating cytoplasmic ribosomes or bacteria. 5. The process was also studied in mitochondrial preparations from rabbit cerebral cortex and spinal cord.     

Enzyme preparations for research on protein hydrolysates and amino acid mixtures not containing peptides

Some properties and the hydrolysing ability of two novel enzyme preparations, a proteolytic preparation "C" from Acremonium chrysogenum (Cephalosporium acremonium) and a peptidase preparation (the producer from the family Pseudomanadaceae), are described. The preparations can be used for obtaining protein hydrolysates with different ratios of free amino acids and peptides. The protein hydrolysis with the preparation "C" enables one to obtain hydrolysates containing 13-18% of free amino acids. The further treatment of the hydrolysates with the peptidase preparation results either in complete hydrolysis of the remained peptide fractions or in obtainment of solutions containing from 60 to 85% of free amino acids and low-molecular weight peptides.