Involvement of D-amino-acid oxidase in D-amino acid utilization in the mouse

Mutant ddY/DAO- mice lacking D-amino-acid oxidase were examined for their ability to utilize D-phenylalanine in place of its L-isomer. Chemically defined milk powder devoid of phenylalanine was used as a basal diet. Adult ddY/DAO- mice and normal ddY/DAO+ mice having D-amino-acid oxidase lost weight every day when fed this diet. However, they maintained their weight when fed the milk powder diet supplemented with 0.33% L-phenylalanine. Although adult ddY/DAO+ mice maintained their weight when fed the milk powder diet supplemented with 0.33% D-phenylalanine, ddY/DAO- mice lost weight while feeding on this diet, which indicated that the ddY/DAO- mice could not utilize D-phenylalanine in place of its L-isomer. Both ddY/DAO- and ddY/DAO+ mice maintained their weight when feeding on the milk powder diet enriched with 0.41% sodium phenylpyruvate, which suggested to us that the ddY/DAO- mice had the ability to invert this alpha-keto acid to L-phenylalanine. Therefore, these results indicate that D-amino-acid oxidase is indispensable for D-amino acid utilization. This is consistent with the concept that D-amino acids are oxidatively deaminated to the corresponding alpha-keto acids by D-amino-acid oxidase and that these keto intermediates are then asymmetrically reaminated to their L-amino acids.     

D-amino acid utilization in infants measured with the 15N-tracer technique

The utilization rates of D-[15N] valine, D-[15N] leucine, D-[15N] phenylalanine and D-[15N] alanine were investigated in seven infants being fed parenterally. Retention of the (15)N in the protein pool varied from one amino acid to another and ranged from 23.2% for D-[15N] valine to 48.6% for D-[15N] alanine. In the case of valine it was shown that cumulative renal excretion amounted to 70% of the applied (15)N-dose, 44% being overflow of unchanged D-[15N] valine, 16.6% appearing as [15N] urea and 1.2% as [15N] ammonium. This indicates that doubling the concentrations of D-amino acid racemates compared with their L-isomer counterparts in parenteral feeding solutions must inevitably lead to imbalances. The use of D-amino acids for the purposes of parenteral nutrition remains however ineffective due to their poor and variable utilization compared to L-amino acids.     

Biophysical and physicochemical methods differentiate highly ligand-efficient human D-amino acid oxidase inhibitors

Many early drug research efforts are too reductionist thereby not delivering key parameters such as kinetics and thermodynamics of target-ligand binding. A set of human D-Amino Acid Oxidase (DAAO) inhibitors 1-6 was applied to demonstrate the impact of key biophysical techniques and physicochemical methods in the differentiation of chemical entities that cannot be adequately distinguished on the basis of their normalized potency (ligand efficiency) values. The resulting biophysical and physicochemical data were related to relevant pharmacodynamic and pharmacokinetic properties. Surface Plasmon Resonance data indicated prolonged target-ligand residence times for 5 and 6 as compared to 1-4, based on the observed k_off values. The Isothermal Titration Calorimetry-derived thermodynamic binding profiles of 1-6 to the DAAO enzyme revealed favorable contributions of both ΔH and ΔS to their ΔG values. Surprisingly, the thermodynamic binding profile of 3 elicited a substantially higher favorable contribution of ΔH to ΔG in comparison with the structurally closely related fused bicyclic acid 4. Molecular dynamics simulations and free energy calculations of 1, 3, and 4 led to novel insights into the thermodynamic properties of the binding process at an atomic level and in the different thermodynamic signatures of 3 and 4. The presented holistic approach is anticipated to facilitate the identification of compounds with best-in-class properties at an early research stage.     

Utilization of riboflavin homologues by D-amino acid oxidase and xanthine oxidase.

D-Amino acid oxidase and xanthine oxidase, two enzymes possessing ionically bound flavin coenzymes have been studied with their flavin coenzymes derived from either 7-ethyl-8-methyl-flavin or 7-methyl-8-ethyl-flavin, vitamin-like homologues of riboflavin. 7-Ethyl-8-methyl-flavin caused a significant reduction of both D-amino acid oxidase and xanthine oxidase in the liver, but not in the kidney. 7-Methyl-8-ethyl-flavin caused a significant reduction of D-amino acid oxidase in both the liver and kidney, a significant reduction of xanthine oxidase in the liver, but a large and significant increase of the latter enzyme in the kidney. An improved procedure for the assay of xanthine oxidase has been described.     

五倍子酸对辐射损伤小鼠造血系统的防护作用

目的 研究中药五倍子的主要有效成分五倍子酸对⁶⁰Co-γ射线诱导的小鼠造血系统损伤的防护作用,并对其作用机制进行初步探讨。方法 实验动物选用ICR小鼠和BALB/c小鼠。分为正常对照组、辐照组、五倍子酸低剂量组（100 mg/kg GA+辐照）、五倍子酸高剂量组（200 mg/kg GA+辐照）和阳性对照组（WR-2721+辐照）共5组。观察五倍子酸对电离辐射诱导的小鼠脾重、脾系数、脾结节形成能力、外周血中WBC、RBC、LYM、PLT数目以及脾脏中凋亡相关蛋白Bax、Bcl-2、P53含量和凋亡相关激酶Caspase3变化的影响。结果 100 mg/kg 和200 mg/kg的五倍子酸能显著减轻辐照所致小鼠脾重下降的程度（P<0.05）,200 mg/kg的五倍子酸能显著改善脾系数下降的程度,并能明显提高受照小鼠脾结节形成能力（P<0.05）。100 mg/kg 和200 mg/kg的五倍子酸能抑制小鼠外周血中RBC、WBC下降的程度,并能明显改善辐射诱导的PLT含量减少（P<0.05）。100 mg/kg 和200 mg/kg的五倍子酸能显著降低小鼠脾脏细胞Bax/Bcl-2 的比值（P<0.05）,但并没有引起p53 和Caspase3水平显著下降（P>0.05）。结论 五倍子酸对辐射所致小鼠损伤具有一定防护作用,其作用机制可能与保护造血系统和减轻细胞凋亡有关。     

Structure of a novel thrombin inhibitor with an uncharged D-amino acid as P1 residue

Thrombin, the ultimate proteinase of the coagulation cascade, is an attractive target for the treatment of a variety of cardiovascular diseases. Previously, a series of novel thrombin inhibitors, discovered by employing a powerful and new computer-assisted multiparameter optimization process (CADDIS), have been synthesized. We have now crystallized the complex of human alpha-thrombin with the most potent of these inhibitors, 8-5 (K(i)=3 nM), and have determined its 2.3A X-ray crystal structure. The Fourier map displayed clear electron density for the inhibitor. The central part of the inhibitor binds in an improved melagatran-like mode, while the structure identifies a d-tyrosine as P1 residue which forms a charged hydrogen bond with Asp 189 of thrombin. This is the first crystal structure of a thrombin-inhibitor complex, where an uncharged inhibitor residue makes hydrogen bonds within the thrombin S1 pocket. Additionally, novel favourable intermolecular hydrogen bonds of the inhibitor with the thrombin backbone become possible due to the d-configuration of the P1 residue. Two flanking voluminous side chains increase the strength of the subjacent hydrogen bonding system by shielding it from the bulk solvent.     

Schistosoma mansoni: decay of resistance induced by gamma irradiated cercariae in the mouse

The level of resistance induced by a single percutaneous infection of cercariae which had been previously exposed to 20 kr of gamma irradiation was compared in two strains of mice. Challenge cercariae were given at several time intervals after the preliminary immunization either to the same skin site as that used for immunization or to a previously unexposed skin site. No significant difference in resistance to infection was observed when a different skin site was used for the challenge. A higher degree of resistance to challenge was observed in CBA/Ca mice than in BALB/c mice. Immunity in both strains declined to about two thirds of the original level after six months and could not be detected when challenge cercariae were given 70 weeks after the single immunizing dose of irradiated cercariae.     

Influence of erythorbic acid on ascorbic acid retention and elimination in the mouse

Large quantities of ascorbic acid or erythorbic acid were administered to Swiss mice over a period of seven months. Urinary ascorbic acid and erythorbic acid were determined two weeks before termination of the experiment. At the end of the experiment, ascorbic acid and erythorbic acid contents in plasma, liver and brain tissues were measured. In the ascorbic acid-treated mice, there was a marked elevation in plasma and urine ascorbate levels, and there was a 38% increase of ascorbate level in the liver but there was no substantial increase in ascorbate levels in the four brain regions studied, namely the cerebrum, cerebellum, medulla and brain stem, upon large intake of ascorbic acid. In the erythorbic acid-treated mice, erythorbic acid is well absorbed by the gastrointestinal tract, enters the blood stream, and is rapidly excreted in the urine. The results show that erythorbic acid is able to replace 45% of ascorbic acid in the liver and 28-39% of ascorbic acid in the brain tissues. Although erythorbic acid appears in the blood at significantly high level, it does not lower blood ascorbate levels.     

Protective effects of an aged garlic extract on doxorubicin-induced cardiotoxicity in the mouse

Protective effects of an aged garlic extract on the cardiotoxicity of doxorubicin (DOX) was evaluated using the mouse. DOX (1.5 mg/kg body wt i.p.) was administered three times per week for 40 days. An aged garlic extract, WG-1 (a preserved stock solution; Wakunaga Pharmaceutical) was administered intraperitoneally six times weekly. DOX caused changes in the electrocardiogram. In the control mice, the width of the QRS complex was 20 +/- 2.8 milliseconds, the R-R interval was 130 +/- 2.8 milliseconds, and the P-Q interval was 30 +/- 1.4 milliseconds. In mice treated with DOX for 40 days, the width of the QRS complex was 50 +/- 10 milliseconds (p < 0.05), the R-R interval was 240 +/- 30 milliseconds (p < 0.05), and the P-Q interval was 45 +/- 1.0 milliseconds (p < 0.01). These values were significantly smaller in mice treated with WG-1 + DOX than in mice treated with DOX. The width of the QRS complex was 29.3 +/- 5.8 milliseconds (p < 0.05), the R-R interval was 145.8 +/- 17.9 milliseconds (p < 0.01), and the P-Q interval was 37.8 +/- 3.5 milliseconds (p < 0.05). The lipid peroxidation in the heart homogenates prepared from DOX-treated mice, as measured by thiobarbituric acid-reactive substance (TBARS, nmol malondialdehyde/100 mg protein) was 332.5 +/- 67.0, which was significantly larger than that in the control mice (186.6 +/- 42.2) (p < 0.05). WG-1 decreased the level of TBARS in DOX-treated mice significantly. In the mice treated with WG-1 + DOX, TBARS was 221.3 +/- 31.6, which was significantly smaller than that of DOX-treated mice (p < 0.05). Histological study demonstrated that the heart treated with DOX had vacuolization in muscle cells, disrupted myofibrils, and swollen mitochondria. Mice that received WG-1 + DOX had no significant pathological lesions in the heart.     

D-氨基酸调节细菌生物被膜解离的研究进展

<正>自然环境和医疗设备中普遍存在细菌生物被膜,往往引起难见治疗成效的慢性感染,探索和开发新的药物以防止细菌生物被膜的形成和/或破坏已形成的生物被膜引起了研究人员极大兴趣。本文就细菌D-氨基酸的生成及其在调节生物被膜解离过程中的作用进行综述。一直以来,人们认为在生命物质中只存在L-氨基酸,随着分析方法的发展,相继在海洋动物、陆生动物、脊椎和无脊椎动物、藻类、种子植物,以     

Direct effects of high concentrations of dimethylsulfoniopropionate, vitamin E and ferulic acid on the senility of aged scenescene-accelerated mouse (SAMP8)

The effects of high concentrations of dimethylsulfoniopropionate (DMSP), vitamin E and ferulic acid solutions on the aging of male and female scenescene-accelerated mouse (SAMP8) at the age of 50 wk were examined by direct supplementation to their stomachs twice a week for 28-30 d. The addition of 1 mL of DMSP, vitamin E and ferulic acid solutions (21% each) to the male and female mice in each group in this order rather elevated their growth and significantly suppressed their total grading score and loss of learning and memory with increasing rearing times for the short experimental period. However, there were no significant differences found between the male and female mice during the experimental period. The antioxidant and hormonal actions for the effects of the test compounds on the aged SAMP8 were possibly considered.     

Extracellular vesicles released from irradiated neonatal mouse cheek tissue increased cell survival after radiation

Alopecia is one of the common symptoms after high-dose radiation exposure. In our experiments, neonatal mice that received 7 Gy X-ray exhibited defects in overall hair growth, except for their cheeks. This phenomenon might suggest that some substances were secreted and prevented hair follicle loss in the infant tissues around their cheeks after radiation damage. In this study, we focused on exosome-like vesicles (ELV) secreted from cheek skin tissues and back skin tissues, as control, and examined their radiation protective effects on mouse fibroblast cell lines. We observed that ELV from irradiated cheek skin showed protective effects from radiation. Our results suggest that ELV from radiation-exposed cheek skin tissue is one of the secreted factors that prevent hair follicle loss after high-dose radiation.     

中老年人群血清尿酸水平和高甘油三酯血症关系的研究

血清尿酸(UA)水平升高与体内核酸代谢异常和肾脏排泄减少相关,高尿酸血症常与传统的心血管危险因素如高血压、高脂血症、2型糖尿病及肥胖等伴发.国内外许多流行病学资料显示,在人群中UA和甘油三酯(TG)之间存在相关性~([1,2]),中老年人群UA和TG更容易发生代谢紊乱,但关于中老年人群UA水平和高甘油三酯血症患病关系的研究较少,为此,本研究利用横断面调查资料探讨中老年人群的上述关系.     

Folic acid supplementation for 4 weeks affects liver morphology in aged rats

Several countries have approved universal folic acid (FA) fortification to prevent neural tube defects and/or high homocysteine levels; this has led to a chronic intake of FA. Traditionally, the vitamin is considered to be safe and nontoxic, except for the potential masking of vitamin B-12 deficiency. Recent reports from our laboratories showed several effects of high-dose folate supplementation in rats. In this work, we compared the effect of FA on the liver of weanling (3 wk) and aged (18 mo) male rats fed either a diet supplemented with 40 mg FA/kg diet or a control diet (1 mg FA/kg diet) for 4 wk. FA supplementation did not alter serum aspartate aminotransferase, alanine aminotransferase, urea, glucose oxidase, total bilirubin, or uric acid. Routine histological staining as well as immunohistochemistry with proliferating cell nuclear antibody for dividing cells, and cytokeratin-8 against bile ductal cells, showed that aged, supplemented rats had the same number of hepatocytes as both control and supplemented weanling rats, and tended to have more (17%, P = 0.07) hepatocytes than aged, control rats. Moreover, the bile duct cells of aged, control rats proliferated and transformed into cholestatic rosettes at a higher frequency than in aged, supplemented rats. The morphology of the liver in weanling rats was similar in both diet groups, and comparable to the supplemented, aged rats, thus indicating that a high intake of FA improves normal liver morphology in livers of aged rats.     

Dietary folic acid intake differentially affects methionine metabolism markers and hippoccampus morphology in aged rats

Purpose

Folic acid (FA) is an emerging nutritional factor in the pathogenesis of diverse neurodegenerative disorders by still unknown mechanisms. The hippocampus is altered during the loss of cognitive abilities in humans and selectively affected when homocysteine increases. The aim was to evaluate the potential protective role of folic acid in the maintenance of biochemical markers related to the methionine cycle, as well as the integrity of the hippocampus as part of the brain in aged rats.

Methods

Male Sprague–Dawley rats (18 months old) were assigned to four different folic acid groups (0 mg FA/kg diet, deficient; 2 mg FA/kg diet, control; 8 mg FA/kg diet, moderate supplementation; 40 mg FA/kg diet, extra supplementation) for 30 days. We evaluated several parameters related to the methionine cycle. In addition, hippocampus areas were immunostained for specific neuronal markers and astrocytes.

Results

Serum folate levels increased according to FA dietary level (p < 0.01). There was a significant increase in the serum homocysteine concentrations in the folic acid-deficient diet group (p < 0.01). However, brain S-adenosylmethionine and S-adenosylhomocysteine did not differ significantly between the folic acid groups. Consequently, the methylation ratio was also unchanged. The morphometric analysis did not show any differences in the number of neurons and astrocytes between groups, except when comparing the folic acid-deficient diet versus folic acid-supplemented diet in the striatum of the hippocampus.

Conclusions

Clearly, the dietary FA deficiency negatively affects the methionine metabolism biomarkers, while excessive supplementation seems to be unnecessary for optimal maintenance of the methylation cycle and hippocampus integrity.