Diet-induced hypercholesterolemia in mice: prevention by overexpression of LDL receptors

The current studies were designed to determine whether chronic overexpression of low density lipoprotein (LDL) receptors in the liver would protect mice from the increase in plasma LDL-cholesterol that is induced by high-fat diets. A line of transgenic mice was studied that express the human LDL receptor gene in the liver under control of the transferrin promoter. When fed a diet containing cholesterol, saturated fat, and bile acids for 3 weeks, the transgenic mice, in contrast to normal mice, did not develop a detectable increase in plasma LDL. The current data indicate that unregulated overexpression of LDL receptors can protect against diet-induced hypercholesterolemia in mice.     

Heritable allele-specific differences in amounts of apoB and low-density lipoproteins in plasma

Low-density lipoprotein (LDL) concentrations correlate with risk of coronary heart disease, and genetic variation affecting LDL levels influences atherosclerosis susceptibility. The principal LDL protein is apolipoprotein B (apoB); apoB is not exchangeable between lipoprotein particles and there is only one apoB per LDL particle. Plasma LDL therefore consists of two populations, one containing apoB derived from the maternal and one from the paternal apoB alleles. Products of the apob gene with high or low affinity for the MB-19 monoclonal antibody can be distinguished, and this antibody was used to identify heterozygotes with allele-specific differences in the amount of apoB in their plasma. A family study confirmed that the unequal expression phenotype was inherited in an autosomal dominant manner and was linked to the apob gene locus. Significant apoB genetic variation affecting plasma LDL levels may be more common than previously appreciated.     

苜蓿总黄酮对小鼠脂类代谢及氧自由基的影响

试验结果显示：灌胃给予苜蓿总黄酮（TFA）的小鼠全血中甘油三酯（TG）和低密度脂蛋白胆固醇（LDL—C）的含量明显降低（P〈0．05）,而高密度脂蛋白胆固醇（HDL—C）含量升高,而且其肝脏和肾脏组织匀浆中过氧化物歧化酶（SOD）的活性显著升高（P〈0．05）,丙二醛（MDA）的含量降低。因此得出结论：TFA具有降血脂、降低低密度脂蛋白胆固醇含量、预防和减轻动脉硬化的作用;同时也具有抑制氧自由基损伤、防止脂质过氧化的作用。     

Vitamin K and coumarin anticoagulants: dependence of anticoagulant effect on inhibition of vitamin K transport

Coumarin anticoagulants inhibit the release of plasma clotting factor VII by vitamin K in liver slices from vitamin K-deficient animals without inhibition of protein synthesis. When the ratio of vitamin K to coumarin anticoagulant is kept constant, but the concentrations are increased, the inhibition disappears. This suggests that the pharmacological action of coumarin anticoagulants depends on irreversible inhibition of normal vitamin K transport to its site of action. At higher concentrations of vitamin K the inhibition can be surmounted, because vitamin K can enter the cell by an alternate route that is not inhibited by coumarin anticoagulants.     

Malondialdehyde-altered protein occurs in atheroma of Watanabe heritable hyperlipidemic rabbits

It has been proposed that chemically reactive lipids released during lipid peroxidation convert low density lipoprotein (LDL), the major carrier of plasma cholesterol, to an abnormal form and that receptor-mediated clearance of this altered LDL produces cholesteryl ester deposition in macrophage-derived foam cells of atheroma. Immuno-cytochemical analyses now reveal the presence of protein modified by malondialdehyde, a peroxidative end product, which colocalizes with the extracellular deposition of apolipoprotein B-100 protein of LDL in atheroma from Watanabe heritable hyperlipidemic rabbits. These findings provide direct evidence for the existence in vivo of protein modified by a physiological product of lipid peroxidation within arterial lesions.     

Deletion in cysteine-rich region of LDL receptor impedes transport to cell surface in WHHL rabbit

The Watanabe heritable hyperlipidemic (WHHL) rabbit, an animal with familial hypercholesterolemia, produces a mutant receptor for plasma low-density lipoprotein (LDL) that is not transported to the cell surface at a normal rate. Cloning and sequencing of complementary DNA's from normal and WHHL rabbits, shows that this defect arises from an in-frame deletion of 12 nucleotides that eliminates four amino acids from the cysteine-rich ligand binding domain of the LDL receptor. A similar mutation, detected by S1 nuclease mapping of LDL receptor messenger RNA, occurred in a patient with familial hypercholesterolemia whose receptor also fails to be transported to the cell surface. These findings suggest that animal cells may have fail-safe mechanisms that prevent the surface expression of improperly folded proteins with unpaired or improperly bonded cysteine residues.     

渗透胁迫下小麦幼苗根质膜ATP酶活性与膜透性的关系

经-1．0MP。聚乙二醇PEG渗透胁迫处理72h的小麦根系质膜透性可逆升高，抗旱品种（陕合6号）增幅小于干旱敏感品种（郑引1号），反复胁迫易导致质膜透性的不可逆伤害；PMH^＋-ATPase活性降低下降比质膜透性严重受伤害早，且不易恢复，可能是渗透胁迫伤害的原初作用点；PMCa^2＋-ATPase活性强弱取决于小麦抗旱性强弱；渗透胁迫下的质膜透性变化与PM ATPase活性变化不呈现直接相关。     

鲤鱼抗体形成细胞分布的研究

用辣根过氧化物酶免疲鲤鱼,再通过免疫组化方法显示其抗体形成细胞(AFC)。AFC在头肾中分布的数量最多,其次是体肾和胸腺,脾脏较少。心脏、肝脏、睾丸及卵巢中未发现有AFC。酶抗酶技术(PAP法)显示:胸腺、头肾、体肾及脾脏中的淋巴细胞大多呈细胞膜表面免疫球蛋白阳性(SmIg~ );细胞质免疫球蛋白阳性(CIg~ )细胞的数量以头肾最多,体肾和脾次之,胸腺较少。可以推测:头肾是鲤鱼的主要免疫反应器官,体肾次之,脾脏在免疫应答中不起主要作用。胸腺中有大量的SmIg~ 细胞,而AFC却较少,表明胸腺虽可以合成抗体,但它主要是培育淋巴细胞的场所。     

肉鸭血浆脂类浓度与体脂含量关系的研究

以42日龄樱桃谷肉鸭(公、母各30只)为试验素材,测定其血浆甘油三酯、磷脂、胆固醇、高密度脂蛋白(HDL)、低密度脂蛋白(LDL)和极低密度脂蛋白(VLDL)的浓度,并屠宰测定其皮脂重(率)、腹脂重(率)和胸、腿肌肉的含脂率.结果表明公鸭血浆胆固醇、LDL、HDL和VLDL浓度极显著高于母鸭;肉鸭血浆胆固醇与甘油三酯呈显著相关,与HDL、LDL、磷脂呈极显著相关,血浆甘油三酯与LDL、VLDL呈极显著相关.HDL与LDL、磷脂呈极显著相关;LDL与磷脂、VLDL呈极显著相关;血浆胆固醇、甘油三酯、HDL、LDL、磷脂浓度与体脂性状相关均较弱,而血浆VLDL浓度与皮脂重、皮脂率、腹脂重呈显著负相关.     

Overexpression of low density lipoprotein (LDL) receptor eliminates LDL from plasma in transgenic mice

A complementary DNA encoding the human low density lipoprotein (LDL) receptor under control of the mouse metallothionein-I promoter was injected into fertilized mouse eggs, and a strain of mice expressing high levels of LDL receptors was established. After administration of cadmium, these mice cleared intravenously injected 125I-labeled LDL from blood eight to ten times more rapidly than did normal mice. The plasma concentrations of apoproteins B-100 and E, the two ligands for the LDL receptor, declined by more than 90 percent after cadmium treatment, but the concentration of another apoprotein, A-I, was unaffected. Therefore, overexpression of an endocytotic receptor can dramatically lower the ambient concentration of its ligand in vivo.     

Construction of synthetic immunogen: use of new T-helper epitope on malaria circumsporozoite protein

The circumsporozoite (CS) protein of Plasmodium falciparum is the focus of intense efforts to develop an antisporozoite malaria vaccine. Localization of sites for T-cell recognition on this molecule is critical for vaccine design. By using an algorithm designed to predict T-cell sites and a large panel of H-2 congenic mice, a major nonrepetitive T-cell site was located. When a synthetic peptide corresponding to this site was covalently linked to the major B-cell site on the molecule, an immunogen capable of eliciting a high-titer antibody response was formed. This peptide sequence could prime helper T cells for a secondary response to the intact CS protein. The new helper T-cell site is located outside the repetitive region of the CS protein and appears to be the immunodominant T site on the molecule. This approach should be useful in the rational design and construction of vaccines.     

丙硫苯咪唑在兔组织内的代谢动力学

本文以高效液相色谱(HPLC)法研究了广谱抗蠕虫药丙硫苯咪唑在兔体内的动力学特征。检测了兔以20mg/kg 单剂量 ig 后,血浆及心、肝、肾、肌肉等组织中丙硫苯咪唑、代谢物亚砜及砜、药物总浓度的 Tmax,Cmax,t(1/2),AUC 等药动学参数;分析了血浆及各组织中丙硫苯咪唑及其代谢物的相对比例;对血药总浓度与各组织中药物总浓度,组织药物总浓度与血浆药物总浓度的比值,对相应给药后的时间进行了回归分析。     

吡喹酮及其主要代谢产物在草鱼体内代谢动力学研究

[目的]研究吡喹酮及其主要代谢产物在草鱼体内的代谢动力学规律。[方法]运用高效液相色谱法(HPLC),研究淡水草鱼在单次口灌给药10 mg/kg剂量条件下,鱼体各组织中吡喹酮(PZQ)及吡喹酮一羟基代谢物(M1)的药动学差异。[结果]草鱼血浆、肠道、肝脏和肾脏内PZQ在各个时间点的药物浓度存在极显著差异(P0.01);PZQ在血浆、肠道、肝脏和肾脏的达峰时间分别为1.0、0.5、1.0和1.0 h,而药物峰浓度为0.41、0.45、0.72和0.44 mg/L,M1在血浆、肠道、肝脏和肾脏的达峰时间分别为48.0、0.5、6.0和48.0 h,而药物峰浓度为0.72、0.45、0.42和0.42 mg/g。这表明PZQ在草鱼体内吸收分布快,M1的达峰时间滞后于PZQ。二者达峰浓度相似表明M1是PZQ在草鱼体内主要代谢物。PZQ在血浆、肠道、肝脏和肾脏的消除半衰期(t_(1/2))分别为16.41、4.77、37.16和8.74 h,M1在血浆、肠道、肝脏和肾脏的消除半衰期(t_(1/2))分别为124、71、246和162 h,其消除半衰期明显比PZQ长,说明在鱼体中M1的残留时间比PZQ更长。[结论]在实际生产中,应注意对M1的检测。     

Three-dimensional structure of the LDL receptor-binding domain of human apolipoprotein E

Human apolipoprotein E, a blood plasma protein, mediates the transport and uptake of cholesterol and lipid by way of its high affinity interaction with different cellular receptors, including the low-density lipoprotein (LDL) receptor. The three-dimensional structure of the LDL receptor-binding domain of apoE has been determined at 2.5 angstrom resolution by x-ray crystallography. The protein forms an unusually elongated (65 angstroms) four-helix bundle, with the helices apparently stabilized by a tightly packed hydrophobic core that includes leucine zipper-type interactions and by numerous salt bridges on the mostly charged surface. Basic amino acids important for LDL receptor binding are clustered into a surface patch on one long helix. This structure provides the basis for understanding the behavior of naturally occurring mutants that can lead to atherosclerosis.     

Mutation in LDL receptor: Alu-Alu recombination deletes exons encoding transmembrane and cytoplasmic domains

The molecular size of the plasma LDL (low density lipoprotein) receptor synthesized by cultured fibroblasts from a patient with the internalization-defective form of familial hypercholesterolemia (FH 274) was smaller by 10,000 daltons than the size of the normal LDL receptor. The segment of the gene encoding the truncated portion of the FH 274 receptor was cloned into bacteriophage lambda. Comparison of the nucleotide sequences of the normal and FH 274 genes revealed a 5-kilobase deletion, which eliminated the exons encoding the membrane-spanning region and the carboxyl terminal cytoplasmic domain of the receptor. The deletion appeared to be caused by a novel intrastrand recombination between two repetitive sequences of the Alu family that were oriented in opposite directions. The truncated receptors lack membrane-spanning regions and cytoplasmic domains; they are largely secreted into the culture medium, but a small fraction remains adherent to the cell surface. The surface-adherent receptors bind LDL, but they are unable to cluster in coated pits, thus explaining the internalization-defective phenotype.     

A portal blood factor as the humoral agent in liver regeneration

It was demonstrated, by use of extracorporeal cross-circulation, that a humoral factor responsible for liver regeneration does not arise from the liver remnant. While intact livers of normal rats incorporated [methyl-(3)H]- thymidine in proportion to the amount of liver removed in the partner, the greatest response occurred after a total hepatectomy. Evidence from portacaval-shunted,partially hepatectomized animals connected to normal members indicates that the factor is in portal blood and that the onset of regeneration is the result of a quantitative imbalance between the available portal blood factor and the number of liver cells present.     

奶牛酮病与胰岛素抵抗关系探讨

为探讨奶牛酮病与胰岛素抵抗的关系,选取产后14 d的酮病组(T)16头和健康对照组(C) 24头奶牛,比较酮病与对照组在能量平衡、肝功能状况、氧化应激、胰岛素敏感性以及耐糖量试验的差异.结果显示:酮病奶牛机体处于能量负平衡状态;肝功能指标中酮病组奶牛血浆天门冬氨酸转移酶、直接胆红素含量极显著高于健康对照组(P＜0.01),总胆红素含量显著高于健康对照组(P＜0.05),胆碱酯酶含量极显著低于健康对照组(P＜0.01),总蛋白含量显著低于健康对照组(P＜0.05),丙氨酸氨基转移酶、间接胆红素、白蛋白、球蛋白含量与健康对照组差异不显著,表明病牛肝脏受到一定程度的损害;酮病组奶牛血浆丙二醛、超氧化歧化酶含量显著高于健康对照组(P＜0.05),表明病牛处于氧化应激状态;酮病奶牛血浆胰岛素敏感指数显著低于健康对照组(P＜0.05),表明病牛的胰岛素敏感性下降.葡萄糖耐量试验显示部分酮病奶牛血糖含量显著高于健康对照组(P＜0.05),在注射完葡萄糖120min后血糖浓度高达4.24 mmol/L,组间差异极显著(P=0.006),表明病牛存在胰岛素抵抗.奶牛酮病与胰岛素抵抗存在密切的关系,可能与肝功能与氧化应激有关.     

Alpha 1 antitrypsinin the livers of patients with emphysema

Parenchymal liver cells from emphysema patients with an inherited deficiency of alpha(1)-antitrypsin contain globules of glycoprotein that bind fluorescent antibody to alpha(1)-antitrypsin. The globules can be seen after hematoxylin and eosinstaining or on electron microscopy, but are more readily demonstrated by PAS stain of amylase-treated liver sections. It appears that an inappropriately large amount of alpha(1)-antitrypsin is found in the liver even when there is a deficiency in the serum. Genetic variants of the normal antitrypsin molecule may be unable to leave their site of synthesis in the liver cell because of some molecular aberration.     

Hepatic synthesis of alpha 2 (acute phase)-globulin of rat plasma

Synthesis of plasma alpha(2) (acute phase)-globulin was demonstrated in isolated perfused rat liver obtained from animals showing acute inflammatory reaction to injury. These findings indicate that the liver is a source of the globulin and that appearance of this protein in the serum results from de novo synthesis by the liver rather than from release of performed and stored globulin.     

The role of hemoglobin denaturation and band 3 clustering in red blood cell aging

As hemoglobin begins to denature, it forms hemichromes that cross-link the major erythrocyte membrane-spanning protein, band 3, into clusters. These clusters provide the recognition site for antibodies directed against senescent cells. These antibodies bind to the aged red cell and trigger its removal from circulation.