生物活性肽-蛋氨酸脑啡肽对成骨细胞增殖的影响

蛋氨酸脑啡肽（Methionine Enkephalin,MENK）作为内源性物质,通过与阿片受体结合,发挥阿片样物质的生物学作用。研究表明,MENK在成熟的骨组织和成骨细胞中均有分布,并且在成骨细胞表面发现了阿片受体。实验旨在进一步研究MENK对成骨细胞增殖的影响。体外培养MC3T3-E1成骨细胞,MTT方法检测MENK对成骨细胞增殖的影响。结果表明,10-7、10-8、10-9mol/L的MENK对成骨细胞的增殖具有促进作用（P〈0.05）。提示MENK可在骨缺损疾病中发挥促进骨组织重建的作用。     

Endogenous Signaling Complexity in Neuropeptides- Leucine- and Methionine-Enkephalin

1. In addition to his many fine contributions in furthering our understanding of the neurochemical action of ecosanoids, catchelomines, steroids, anandamines, cannabinoids, endorphins, and the many modifications made to these neural factors, twenty years ago Julius Axelrod published a noteworthy paper concerning the nature of neuropeptides and their potential for multiple neurophysiological effects (Redgate et al., 1986).2. In that report, Axelrod and coworkers described the neurological actions of the then recently discovered leucine- and methionine-enkephalins, and their biological functions which were novel, atypical, and in possession of neurological effects that were significantly “much more than additive.”3. In this short communication I would like to expand on this observation concerning the “additive effects” contained within the amino acid sequence of the atypical neurotransmitter peptides leucine- and methonine-enkephalin.     

高盐饮食对大鼠血压和脑内脑啡肽含量的影响

大鼠47只,高盐饮食饲养4个月后,尾部收缩期血压为135±2mmHg((?)±SEM),较对照组(40只)102±1mmHg明显升高(P<0.001)。高盐饮食组大鼠的纹状体和脑干的甲硫氨酸脑啡肽(MEK)和亮氨酸脑啡肽(LEK)的含量,均较对照组明显增加(p<0.01),下丘脑区亦增加(P<0.01或P<0.05),而丘脑和海马区与对照组相比,无显著差别。高盐饮食组大鼠血浆中的血管紧张素Ⅰ浓度,比对照组为低(P<0.05)。     

Cell-free translation of human pheochromocytoma messenger RNA yields protein(s) containing methionine-enkephalin

Cell-free translation of messenger RNA extracted from a human pheochromocytoma yields protein(s) of apparent molecular weight >70,000 daltons which contain the pentapeptide methionine-enkephalin. It is estimated that 0.8–1.0% of the total pheochromocytoma mRNA codes for the methionine-enkephalin-containing protein, based on percent incorporation of [³⁵S]methionine into methionine-enkephalin during cell-free translation. These results demonstrate that human pheochromocytoma mRNA contains the message for a high-molecular weight methionine-enkephalin-containing protein or proteins, presumably the methionine-enkephalin precursor molecule(s).     

Radioimmunochemical methods for the quantitative autoradiographic determination of antigens in brain and other tissues

1. We have used horseradish peroxidase-conjugated protein A- and 125I-protein A to develop immunohistochemical and radioimmunohistochemical methods for the localization of antigens in brain and other tissues of the rat. 2. We visualized methionine-enkephalin fibers in the rat brain by incubating tissue sections with a specific polyclonal antibody and peroxidase-conjugated protein A. The method is simple, fast, and less expensive and more sensitive than classical immunohistochemical techniques and the principle could be used to visualize many other tissue antigens. 3. Incubation of tissue samples with specific polyclonal antibodies and 125I-protein A, followed by autoradiography, allows the permanent recording of the radioimmunohistochemical localization of brain methionine-enkephalin, tyrosine hydroxylase, and angiotensin-converting enzyme and of pituitary vasopressin and could be applied to the localization of many other tissue antigens. 4. A new quantitative radioimmunohistochemical technique for methionine-enkephalin allows the determination of the endogenous peptide content in discrete brain nuclei from 16-microns-thick sections. The method is based on the quantitative determination of the amount of 125I-protein A bound to specific tissue areas after incubation with a specific polyclonal antibody, followed by autoradiography and computerized microdensitometry. To quantify the endogenous peptide content, the values obtained are interpolated into a methionine-enkephalin internal standard curve. This standard curve was constructed by measuring endogenous concentrations of methionine-enkephalin by radioimmunoassay in specific brain regions and correlating these values with quantitative autoradiographic determinations in homologous areas of adjacent sections. Similar methods can be developed for other tissue antigens. 5. These new methods allow for the localization and quantification of tissue antigens in very discrete areas of the brain and other tissues and have a wide application in neurobiology and pathology.     

柄袋沙蠋体壁和消化系统甲硫氨酸脑啡肽免疫组织化学定位

采用免疫组织化学SABC法,对甲硫氨酸脑啡肽(M-ENK)在柄袋沙蠋体壁及其附属物鳃、疣足和消化系统各器官中的分布进行了研究.结果 表明,柄袋沙蠋体壁、鳃、疣足以及各消化器官的上皮细胞中均有不同程度的M-ENK阳性反应,且体壁、消化道的食管、肠、直肠中阳性反应多集中在上皮细胞的游离端;体壁肌肉中环肌层M-ENK阳性反应比纵肌层强;食道侧囊上皮细胞和结缔组织中也有M-ENK分布.M-ENK在柄袋沙蠋的体壁、鳃、疣足及消化系统各器官中均有分布,且分布密度不同,可能与各部位的功能有关.     

β-Endorphin: Characteristics of binding sites in the rabbit cerebellar and brain membranes

Specific binding of human β-endorphin to rabbit cerebellar and brain membranes was measured using $\text{[}{}^3\text{H}{}_2\text{-Tyr}{}^{27}\text{]-β}{}_{\mathrm{h}}\text{-endorphin}$ as the primary ligand. In both tissues binding was time dependent and saturable, with apparent equilibrium dissociation constants of 0.275 nM and 0.449 nM in the cerebellum and brain, respectively. The binding capacity of cerebellum is greater than that of brain. Kinetic studies showed that the association rate constants were 2.7 × 10⁷ M^?1min^?1 for cerebellum and 2.4 × 10⁷ M^?1min^?1 for brain. Dissociation of tritiated β_h-endorphin from both cerebellum and brain is not consistent with a first order decay from a single site. In the cerebellum, these is a time-dependent increase in slowly dissociating complex. The potency of several opioid peptides and opiates to inhibit the binding of tritiated β_h-endorphin was determined. Ligands with preference for μ, δ, and κ opiate receptor (morphine, Metenkephalin and ethylketocyclazocine) all have similar affinities toward β_h-endorphin sites in both brain and cerebellar membranes.     

Thyroid Hormone Replacement Restores Circulating Enkephalin Concentrations in Hypophysectomized Fetal Sheep

Abstract: We have investigated the effects of fetal hypophysectomy (HX) with or without thyroxine (T₄) replacement on the plasma concentrations of free methionine-enkephalin (free Met-Enk), noradrenaline, and adrenaline in late gestation sheep fetus. Plasma adrenaline concentrations were significantly higher in intact fetal sheep (1.05 ± 0.12 pmol/L) between 125 and 140 days of gestation when compared with the HX + saline (0.64 ± 0.10 pmol/L) and HX + T₄ (0.61 ± 0.08 pmol/L) groups. During the first 15 days of the T₄ or saline infusion, the plasma concentrations of free Met-Enk were significantly higher in the HX + T₄ group (392 ± 40 pmol/L) than in the HX + saline group (299 ± 43 pmol/L). At this stage of gestation, however, circulating concentrations of free Met-Enk were significantly higher in intact fetal sheep (556 ± 51 pmol/L) than in either of the HX groups. Between 125 and 140 days of gestation, plasma free Met-Enk concentrations were similar and significantly higher in the intact and HX + T₄ groups than those measured in the HX + saline fetal sheep. We conclude that the decrease in circulating free Met-Enk concentrations after removal of the fetal pituitary is primarily a consequence of functional athyroidism.     

A novel nuclease from mitochondria of rat liver

Alkaline RNase partially purified from rat liver mitochondria hydrolyzes both RNA and denatured DNA. The behaviors of RNase activity of the nuclease are closely similar to those of the DNase activity. The nuclease has a pH optimum between 9.0 and 9.5, and the activity is absolutely dependent on Mg²⁺ and reversibly inhibited by $\text{p}$-hydroxymercuribenzoate.