Chemical Pathways of Peptide Degradation. V. Ascorbic Acid Promotes Rather than Inhibits the Oxidation of Methionine to Methionine Sulfoxide in Small Model Peptides

The effect of primary structure and external conditions on the oxidation of methionine to methionine sulfoxide by the ascorbate/Fe³⁺ system was studied in small model peptides. Degradation kinetics and yield of sulfoxide formation were dependent on the concentration of ascorbate and H⁺, with a maximum rate observed at pH 6–7. Phosphate buffer significantly accelerated the peptide degradation compared to Tris, HEPES, and MOPS buffers; however, the formation of sulfoxide was low. The oxidation could not be inhibited by the addition of EDTA. Other side products besides sulfoxide were observed, indicating the existence of various other pathways. The influence of methionine location at the C terminus, at the N terminus, and in the middle of the sequence was investigated. The presence of histidine in the sequence markedly increased the degradation rate as well as the sulfoxide production. The histidine catalysis of methionine oxidation occurred intramolecularly with a maximum enhancement of the oxidation rate and sulfoxide production when one residue was placed between the histidine and the methionine residue.     

用氟离子选择电极测定牙膏游离氟

用氟离子选择电极测定牙膏中的氟含量，本法测定回收率为９８．６３％～１０４．００％，变异系数为３．８３％。     

电针对大鼠脑局部缺血-再灌流损伤的保护作用

再灌流前电针“环跳”穴３０ｍｉｎ，观察对左大脑中动脉（ＭＣＡ）缺血 再灌流模型大鼠早期运动功能、自由基代谢、脑水肿及神经电生理活动的影响。结果：缺血再灌＋针刺组大鼠再灌流后神经功能缺损状况有较明显的改善，病灶侧脑组织过氧化物歧化酶（ＳＯＤ）活性及丙二醛（ＭＤＡ）含量恢复到接近假手术对照组的水平。皮层体感诱发电位（ＳＥＰ）测量表明缺血侧Ｐ１潜伏期及Ｐ１ Ｎ１波幅亦有显著性改善。结果表明：于再灌流前电针处理对本模型脑缺血 再灌流损伤有保护作用     

The lateral arm free flap in lower extremity reconstruction

Reconstruction of skin defects of the distal third of the leg and foot is often a difficult task. Shape, resistance to shearing stresses in the weight-bearing surface and sensibility are the main features that have to be restored. For coverage of this region, the authors have used, in selected patients, the lateral arm flap (LAF) since 1994. This flap is thin, easy to dissect and has the possibility to be innervated through the posterior cutaneous nerve of the arm. Fourteen cases are presented. The drawbacks of this flap are the loss of sensibility in the forearm (partially transient) and the scar on the arm, which can be rather unsightly in young ladies and when big flaps are harvested skin graft is needed.     

Free flap reconstruction in massive upper extremity burns

In massive burns, early excision and a free flap reconstruction is, in some cases, limb saving. From October 1979 to August 1993, eleven patients with massive burn injury in the upper extremity were treated using a free flap reconstruction. Eight cases were acute or subacute and three were late reconstructions. The following free flaps were used: rectus femoris microneurovascular musculocutaneous flap (2), latissimus dorsi flap (4), rectus abdominis flap (3), gluteal thigh flap (1), lateral arm flap (1), and serratus flap (1). The gluteal thigh flap was lost and it was later replaced by a rectus abdominis flap. In three cases successful reanastomosis was performed. Functional late reconstructions were performed in nine patients. In all eleven patients the limb was saved and functional recovery was satisfactory. We recommend that a free musculocutaneous or muscle flap is used, proximal to the wrist, if after careful excision of nonviable tissue, tendons, bone joint or major vessels are exposed. The rectus femoris musculocutaneous flap is a useful solution to restore extensor musculature of the forearm after extensive injury.     

褐藻中高相对分子质量褐藻多酚的抗氧化活性研究

目的　评价鼠尾藻和海黍子两种褐藻中高相对分子质量褐藻多酚的抗氧化活性。方法　分别利用 3种体系 ,通过对羟自由基 (· OH)、超氧阴离子 ( O÷2 )和 1,1-二苯基 - 2 -苦味肼基自由基 ( DPPH· )清除效率来评价其抗氧化活性。结果　两种褐藻中高相对分子质量褐藻多酚对· OH、O÷2 和 DPPH·均有很高的清除效率 ,且效果相近。结论　鼠尾藻和海黍子两种褐藻中高相对分子质量褐藻多酚具有较强的抗氧化活性 ,是一类潜在的海洋生物天然抗氧化剂。     

SOD和Cu（Ⅱ）络合物脂质体的SOD样活性

用Cyt.c-HX-XO法分别测定了SOD和4种Cu（Ⅱ）络合物及脂质体的SOD样活性，结果表明：所有体系均有某种程度的SOD样活性，其中组氨酸酮脂质体的SOD样活性最高，Cu(Ⅱ）络合物与脂质体具有一些协同作用。     

Surface-related triggering of the neutrophil respiratory burst. Characterization of the response induced by IgG adsorbed to hydrophilic and hydrophobic glass surfaces

Hydrophilic and hydrophobic glass surfaces precoated with human albumin, fibrinogen, or IgG were investigated with respect to their ability to activate the neutrophil NADPH-oxidase. We found that IgG-coated surfaces induced a substantial and prolonged neutrophil production of reactive oxygen species (ROS). When a hydrophilic surface was used to support protein binding, a somewhat lower neutrophil response (around 35%) was obtained, compared with the response induced by IgG on a hydrophobic surface. The production of ROS was completely eliminated when cytochalasin B was added to the measuring system, suggesting the involvement of the cell cytoskeleton in the activation process. The relation between the intra- and extracellular generation of ROS was further assessed, and we found that most of the ROS produced were released from the cells, in agreement with a model in which the activating surfaces induce a ‘frustrated’ phagocytic response. Serum totally inhibited ‘frustrated’ phagocytosis provided that the IgG molecules were sticking to a hydrophilic surface.     

地塞米松对电光性眼炎防治作用的实验研究

本文对电光性眼炎家兔角膜上皮的超氧化物歧化酶（ＳＯＤ）活性及脂质过氧化反应主要代谢产物丙二醛（ＭＤＡ）含量进行测量。发现紫外线照射后３小时ＳＯＤ活性降低，伴随上述改变，ＭＤＡ含量增高。用地塞米松在照射前、后滴眼，３小时检测ＳＯＤ和ＭＤＡ，发现其可保护ＳＯＤ，并降低ＭＤＡ含量。透射电镜下显示，角膜上皮细胞的变化主要在其底部细胞，以水肿性改变为主。实验结果提示自由基损伤在急性电光性眼炎的发生、发展过程中起了重要作用，地塞米松可减轻这种变化。     

The estimation of the plasma free fraction of cyclosporine in rabbits and heart transplant patients: The application of a physiological model of renal clearance

We estimated the free fraction (f_u) of cyclosporine (CyA) in the plasma from concentrations of CyA in urine (C_u) and plasma (C_p), urine flow rate (UF), and glomerular filtration rate in rabbits and in heart transplant patients. Following intravenous administration of CyA (5–30 mg kg^?1) in ten NZW rabbits and oral administration of CyA (4.8–12.1 mg kg^?1) in nine heart transplant patients, CyA concentrations in urine and plasma were measured by HPLC. The ratios of C_u to C_p and UF data were fitted to a physiological model of renal clearance using NONMEM. The free fraction of cyclosporine in the rabbits and the heart transplant patients was 0.0122 and 0.14, respectively. Because of the relatively low permeability of CyA across the tubular epithelium, no apparent equilibrium between C_u and C_p at any urine flow rate was reached and, therefore, the C_u to C_p ratio will not be equal to f_u.