促吸收剂癸酸钠对黄连素在大鼠肠道吸收的促进作用

目的:探讨黄连素(Ber)在大鼠肠道的吸收动力学,阐明癸酸钠(SC)对Ber在小肠段吸收的影响.方法:雄性Wistar大鼠建立在体肠段灌流模型,HPLC法测定不同浓度Ber(50、100和200 μmol·L-1)和Ber与质量浓度为0.2%SC合用在小肠的吸收情况;测定肠灌流液中乳酸脱氢酶(LDH)活性,观察SC对肠道黏膜细胞的损伤.结果:Ber浓度在50～200 μmol·L-1范围内Ber吸收呈浓度依赖性;吸收速率常数(Ka)组间差异无统计学意义(P>0.05);SC能显著提高Ber在小肠的吸收量(P<0.05);SC对Ber吸收速率常数Ka无显著影响(P>0.05);Ber组、SC+Ber组肠循环液中LDH的含量与空白对照组比较差异无统计学意义(P>0.05).结论:Ber在小肠吸收较差,吸收机制为被动扩散,吸收过程为一级动力学过程;SC能显著促进Ber在小肠的吸收,是一种安全、有效的促吸收剂.     

Energetics of isolated hepatocyte swelling induced by sodium co-transported amino acids

Many of the serious, potentially fatal complications of hematopoietic stem cell transplantation have similarities to the multiple organ dysfunction syndrome (MODS) in critically ill nontransplant patients. One of these similarities is the alteration in the hemostatic system in such a way as to lower the levels of the naturally occurring anticoagulant proteins, especially antithrombin III. As in MODS, the outcome of transplant patients with these complications correlates with the degree of change in antithrombin III levels. Preliminary studies suggest that antithrombin III concentrate in pharmacologic doses along with intensive supportive care efforts can improve the clinical outcome of patients with these transplant-related complications. Further work to confirm these findings and, it is hoped, provide insight into the mechanism of action of antithrombin III in this setting is obviously warranted. Until such studies are completed, however, the preponderance of evidence suggests that when subjected to a risk-benefit analysis, patients in the early stages of transplant-related complications would be better off receiving antithrombin III supplementation than not.     

Spasmogenic and potentiating actions of some amino acids on the guinea-pig myometrium

Ectothiorhodospira shaposhnikovii, Chromatium minutissimum and Thiocapsa roseopersicina were grown in the dark under anaerobic conditions on media containing glucose or fructose and organic acids. Their cell contained the following enzymes of the fructose diphosphate pathway: phosphofructokinase, fructose diphosphate aldolase, and 3-phosphoglyceraldehyde dehydrogenase. The activity of fructose diphosphate aldolase was higher in the cells grown in the dark than in the cells grown in the light. The same enzymes of the tricarboxylic acid cycle were found in the cells cultivated in the dark on media containing organic acids as in the cells grown in the light, though the activity of some enzymes was lower. Only the activity of isocitrate lyase increased in the cells cultivated in the dark on a medium containing acetate.     

Effects of amino acids on alcohol intake in stroke-prone spontaneously hypertensive rats

The concentration-dependent effects of several PCB, PCDD, and PCDF congeners and several commercial PCB preparations as antiestrogens were determined in the aryl hydrocarbon (Ah)-responsive MCF-7 human breast cancer cell lines. The inhibition of the 17 beta-estradiol-induced secretion of the 52-kDa protein (procathepsin D) was measured using a combination of polyacrylamide gel electrophoresis, double-staining of the protein bands with ISS ProBlue and silver stain, and quantitation by densitometric analysis. For the PCBs, the order of antiestrogenic potency was 3,3',4,4',5-pentachlorobiphenyl > 3,3',4,4',5,5'-hexachlorobiphenyl approximately 3,3',4,4'-tetrachlorobiphenyl > 2,3,3',4,4',5'-hexa, 2,3,3',4,4'- and 2,3,4,4',5-pentachlorobiphenyl > Aroclors 1221, 1232, 1248, 1254, and 1260 were inactive as antiestrogens at the highest concentrations used in this study (10(-6) M). For the PCDDs and PCDFs, the order of antiestrogenic potency was 2,3,7,8-tetrachlorodibenzo-p-dioxin > 2,3,7,8-tetrachlorodibenzofuran > 2,3,4,7,8-pentachlorodibenzofuran > 1,2,3,7,9-pentachlorodibenzofuran > 1,3,6,8-tetrachlorodibenzofuran. With few exceptions, the order of potency for all these congeners and mixtures paralleled their relative activities as agonists for other Ah receptor-mediated responses and their competitive binding affinities for the Ah receptor. The results of this study support the role for the Ah receptor in mediating the inhibition of the 17 beta-estradiol-induced secretion of the 52-kDa protein in MCF-7 cells and also points out the utility of this technique as a bioassay for this class of compounds.     

Effect of repeated stress on a number of plasma amino acids and related compounds in young and old rats

A number of amino compounds were studied in the plasma of young and old rats exposed to an immobilization stress on 3 different days. Baseline values were similar for all compounds between age groups except for slightly higher phenylalanine levels in old animals. Most differences were seen in the stress responses. Stress response intensities for alanine, aspartic acid, methionine, phenylalanine, and tyrosine were generally higher in old rats and recovery times from stress were usually longer. Although the stress responses decreased in young rats for some compounds over the three exposures, old rats showed no or less adaptation during this time. All the other amino acids showed no marked age effects. This study shows that certain plasma amino acids can serve as selective indicators of biological age and that their stress responses might be better markers of the aging process than their resting levels.     

Regulation of glutamate dehydrogenase by branched-chain amino acids in skeletal muscle from rats and chicks

Neurotrophin-4 (NT-4) is a member of a family of neurotrophic factors, the neurotrophins, that control survival and differentiation of vertebrate neurons (2-4). Besides being the most recently discovered neurotrophin in mammals, and the least well understood, several aspects distinguish NT-4 from other members of the neurotrophin family. It is the most divergent member and, in contrast to the other neurotrophins, its expression is ubiquitous and appears to be less influenced by environmental signals. NT-4 seems to have the unique requirement of binding to the low-affinity neurotrophin receptor (p75LNGFR) for efficient signalling and retrograde transport in neurons. Moreover, while all other neurotrophin knock-outs have proven lethal during early postnatal development, mice deficient in NT-4 have so far only shown minor cellular deficits and develop normally to adulthood. Is NT-4 a recent addition to the neurotrophic factor repertoire in search of a crucial function, or is it an evolutionary relic, a kind of wisdom tooth of the neurotrophin family?     

Effect of osmotic stress on tissue free amino acids in Pila virens

Tolerated doses of phalloidin, a toxin from the mushroom Amanita phalloides, protect mice against lethal doses of phalloidin. Resistance is conferred by the 1/10 LD95 of phalloidin and sets in at about 8 hours after the pretreatment.     

Effect of melatonin on the heart rate variability caused by lesions of the dorsal hippocampus in rats

Bilateral lesions of the hippocampus induced irregular shifts of the heart rate variability in rats. The shifts could be prevented with melatonin but not with diazepam.     

Effect of infusion of hypertonic saline solution of conscious heifers with hypoxemia caused by endotoxin infusion

Thirty male Sprague-Dawley rats were given ciclosporin (Cs) orally, 15 mg/kg daily for 80 days. Fifteen served as positive controls, while the other 15 were given daily colchicine at a dose of 30 microg/kg in addition to Cs. Additional 15 rats were given olive oil only and served as negative controls. The animals were subjected every other week to laboratory assessment of serum creatinine, sodium, potassium, and Cs whole-blood trough levels; also urine samples were examined for creatinine, sodium, potassium, and protein concentrations. At the end point, the animals were sacrificed, and kidney tissue was examined for histopathological changes. Comparing negative control versus Cs-treated and Cs-plus-colchicine-treated rats, there were no significant differences in serum creatinine, creatinine clearance, and serum and urine values of sodium and potassium as well as urinary protein/creatinine ratios. Yet histopathological examination of kidney tissues showed focal tubular atrophy and interstitial fibrosis in inner medulla and inner stripe of the outer medulla in all Cs-treated animals and in only 1 of the colchicine-treated group, but in none of the negative controls. Histological changes in other kidney zones in different animal groups were minor and not different. From this study, we may conclude that colchicine is of protective value against chronic Cs nephrotoxicity in Sprague-Dawley rats.     

Effect of salts on the interaction of oxidized glutathione with dibasic amino acids

This paper presents a Fourier rebinning algorithm for three-dimensional image reconstruction in PET that incorporates the concept of spectral transfer function. It suggests the need for discarding low-frequency components in the rebinning. It also includes the correction for rebinning efficiency which was evaluated by simulations as a function of oblique angle of projections. The performance was optimized by high-pass filters and axial smoothing. The algorithm yields satisfactory images with negligible axial cross-talk for a maximum oblique angle up to 26.6 degrees. The statistical noise was evaluated in terms of 'noise equivalent number of oblique angles', and reasonable results were obtained in view of the theoretical expectation. Ring artefacts due to noise are negligibly small.     

Correlation of blood and brain amino acids in hypoglycemic and normoglycemic rats

Utilization of gluconeogenic amino acids as a source of energy by brain can occur in starved newborn rats. This capacity is lost later in life as evidenced by changing ratios in blood and brain concentrations between fed and fasted animals.     

Effect of amino acids on purified rat intestinal brush-border membrane aminooligopeptidase

When a hexapeptide, Leu-Trp-Met-Arg-Phe-Ala, or a pentoapeptide, Leu-Trp-Met-Arg-Phe, was incubated in vitro with a purified aminooligopeptidase from rat small intestinal mucosa, the respective C-terminal dipeptides, Phe-Ala and Arg-Phe, were observed to be resistant to hydrolysis. The resistance of these C-terminal dipeptides to hydrolysis was found to be due mainly to the accumulation of inhibitory hydrophobic amino acids liberated in the incubation mixture. The hydrolysis of various peptides by the brush-border membrane peptidase is inhibited to a varying extent by the hydrophobic amino acids L-tryptophan, L-methionine, L-isoleucine, L-leucine, L-tyrosine, and L-phenylalanine, but not the D-form of these amino acids. The inhibition of the hydrolysis of three dipeptides by hydrophobic amino acids showed these amino acids to be competitive inhibitors (same Vmax, the maximal velocity of the enzyme reaction; different Km, the substrate concentration at which the enzyme reaction is half maximal) of one of the dipeptides while exhibiting a mode of inhibition that was not competitive (different Vmax, different Km) with either of the other two dipeptides. These data indicate that the effect of amino acids on the hydrolytic rate of the brush-border membrane aminooligopeptidases must be considered in studies of intestinal hydrolysis and absorption of peptides.     

Production of amino acids by yogurt bacteria

The dynamics of free amino acid production by the selected strains Streptococcus thermophilus 13a and Lactobacillus bulgaricus 2-11 were studied in pure and mixed cultivations during yogurt starter culture manufacture. L. bulgaricus 2-11 showed the highest activity for producing free amino acids with high individual concentrations over the first hour of growth (50% of the total amount). By the end of milk's full coagulation (4.5 h), 70% of the total amount of amino acids was released. S. thermophilus 13a showed poor proteolytic properties and consumed up to 70% of the free amino acids produced by L. bulgaricus 2-11 in the process of coagulation of milk with the mixed culture.     

Effects of stress on amino acids and related compounds in various tissues of fasted rats

The purpose of this study was to examine the effect of stress on the free amino acid pattern of plasma and various organs. Two groups of rats were deprived of food, for 24 hrs. One group was sacrificed after this time (fasting control representing mostly free endogenous amino acids) and the second group was first restrained in wire cages for 120 min before being sacrificed (fasting stress representing mostly the effects of stress on endogenous free amino acids). A third group had free access to food and was sacrificed at the same time (fed control representing mostly free amino acids absorbed from the gut and endogenous free amino acid metabolism). Fasting (as compared to fed controls) reduced alanine and arginine but increased ethanolamine, glutamic acid and glutamine in the plasma; increased ethanolamine, phosphoethanolamine and glutamic acid in the liver; increased carnosine, glutamic acid, phosphoethanolamine and glutamine in the ventricle; increased oxidized glutathione in the aorta; decreased alanine, aspartic acid, glutamic acid, leucine and methionine and increased glutamine in the pancreas; and decreased arginine in skeletal muscle. Fasting plus stress (as compared to fasting controls) reduced alanine and glutamine in the plasma; increased methionine in the liver; increased ethanolamine, GABA, and glutamic acid in the aorta; reduced arginine, glutamic acid, glutamine, leucine and methionine but increased ethanolamine in the ventricle; reduced ammonia and ethanolamine but increased histidine, isoleucine, leucine, lysine, phenylalanine, tyrosine and valine in the pancreas; and reduced ammonia in skeletal muscle. Fasting plus stress affects the amino acid composition of plasma and various of tissues but effects seen were individually different and strongly substance and tissue specific. Plasma changes did not coincide with tissue changes. Changes in the endogenous pattern of amino acids and related compounds in response to stress could be first indications of stress induced organ pathology.     

Effect of cycloleucine on renal uptake of dibasic amino acids and cystine

In 24% (18 out of 76) small-for-dates a "significant" though asymptomatic hypoglycemia was demonstrated during the first six hours of life. The cord blood glucose concentration was lower in the hypoglycemic compared to that of the small-for-date normoglycemic group. In the hypoglycemic infants, the disappearance rate of glucose was significantly elevated and the lipid mobilization disturbed. It is suggested that a lack of lipids for energy metabolism increases the glucose expenditure and hence increases the risk for hypoglycemia.     

Effect of undernutrition and amino acid deficiency on the timing of puberty in rats

Sexual maturation was examined in underfed or amino acid-deficient rats. We have demonstrated a highly significant negative linear relationship (r = -0.80, P less than 0.001) between the age at puberty and the growth rate in rats under conditions of food restriction. The weight at puberty in animals growing at different rates because of undernutrition was not constant but behaved as a quadratic function of growth rate, as predicted from the assumption that growth rate was an independent variable. Growth rate is therefore more important than arrival at a particular fixed weight in determining the timing of puberty. Feeding of low valine diets resulted in delayed sexual maturation. Both the weight at vaginal opening (182 +/- 5.9 g) and the weight at first estrus (187 +/- 6.1 g) were significantly greater in the valine-deficient group when compared with growth-matched control (139 +/- 10.7 g and 161 +/- 9.3 g, respectively, P less than 0.05). The valine-deficient group also had significantly later vaginal opening (98.8+/- 4.7 days) than growth-matched controls (76.6 +/- 6.6 days, P less than 0.02). Valine deficiency seemed to have a specific effect on the hypothalamic-pituitary-gonadal axis since puberty in valine-deficient animals was delayed more than could be accounted for by impairment of growth.     

Resolution of enantiomers of amino acids by HPLC

Application of HPLC as a prime tool in the area of enantiomeric resolution has opened doors of success and varied interest. Use of chiral reagents either indirectly (as derivatization reagent) or directly (added to stationary or mobile phase) has led to achieve resolution of a wide range of compounds. Amino acids, being important molecules with simple structure and easy availability, have been extensively studied. A bibliographic survey on HPLC resolution of amino acids and derivatives along with a brief discussion on general methods of enantiomeric separation has been presented.