Histone phosphorylation: stimulation by adenosine 3',5'-monophosphate

Adenosine cyclic 3',5'-monophosphate at a concentration of 10-(7)M causes a four-to sixfold increase in the rate of histone phosphorylation catalyzed by a liver enzyme preparation. This observation suggests a mechanism for the induction of RNA synthesis by those hormones that cause increases in the concentration of cyclic AMP.     

Turnover of rat liver tyrosine transaminase: stabilization after inhibition of protein synthesis

Turnover of the rat liver tyrosine transaminase in vivo was measured by a label and chase procedure under conditions where the amount of enzyme undergoes no change. Half-life of the (14)C-labeled enzyme in this basal condition was found to be 1.5 +/- 0.3 hours. Inhibitors of protein synthesis (cycloheximide or puromycin) do not appreciably influence the basal enzyme level over a 5-hour period, although these drugs will block hormonal induction of this enzyme. In pulse-labeling experiments, cycloheximide blocked transaminase synthesis almost completely. The conclusion that enzyme degradation, as well as synthesis, must be blocked when protein synthesis is stopped was confirmed in experiments showing that labeled enzyme is stable in the liver of rats treated with cycloheximide The participation of a continuously synthesized polypeptide in the degradative phase of transaminase turnover is suggested.     

Significance of mitochondria for porphyrin and heme biosynthesis

It is concluded that mitochondria are involved in three steps of porphyrin and heme biosynthesis-first, in the formation of delta-aminolevulinic acid from glycine and active succinate; second, in the synthesis of protoporphyrin; third, in the incorporation of iron into the porphyrin ring-that is, in heme formation.     

氨基取代四苯基卟啉衍生物的结构剖析

用 HMO 方法计算了5个氨基取代四苯基卟啉的能级、净电荷、自由价和共振能,讨论了这些参数之间的线性关系,并预测了这类大环化合物的酸碱性。     

Failure of cycloheximide to induce tyrosine transaminase in the anesthetized rat

It was recently reported that cycloheximide, an inhibitor of protein synthesis, induces tyrosine transaminase in the liver of adrenalectomized rats. We have been unable to confirm this effect in the anesthetized animal and our data show that cycloheximide inhibits the induction caused by hydrocortisone in adrenalectomized rats or by stress in intact rats.     

Carcinogens 3,4-benzpyrene and 3-methylcholanthrene: induction of mitochondrial oxidative enzymes

Sections of liver from rats injected with 3,4-benzpyrene and 3-methylcholanthrene, when incubated in mediums specific for the histochemical demonstration of mitochondrial oxidative enzymes, show greater activity of several of these enzymes than do sections from control rats. This observation was confirmed by comparison of the staining of mitochondria isolated from the control and from "induced" rats. The fact that an inhibitor of protein synthesis, actinomycin D, effectively diminished the stimulation provided evidence that the stimulation of activity is due to an increase in enzyme synthesis, generally called induction.     

Search for porphyrins in lunar dust

Evidence for porphyrins was obtained in the Apollo 11 bulk sample of lunar dust by fluorescence spectrometry and analytical demetallation. The indicated porphyrins showed major fluorescence excitation at 390 nanometers. Abundance was about 10(-10) gram of porphyrin per gram of dust. Similar pigments were found in exhaust products from tests of a lunar descent engine. The similarity of results suggests that most if not all of the indicated porphyrin aggregate of the lunar sample probably was synthesized from rocket fuel during the landing of the lunar module. These compounds may be the product of a novel high-temperature synthesis of cosmochemical interest.     

Reversal of catecholamine refractoriness by inhibitors of RNA and protein synthesis

The generation of adenosine 3',5'-monophosphate (cyclic AMP) in response to catecholamines in the 2B subclone of RGC6 rat glioma cells previously exposed to norepinephrine and refractory to further norepinephrine addition is substantially increased by addition of inhibitors of RNA and protein synthesis. The time course of the effect of these inhibitors on cyclic AMP concentration suggests that rapid protein synthesis and turnover are involved in catecholamine refractoriness. Norepinephrine induction of cyclic nucleotide phosphodiesterase is demonstrable in RGC6 cells but not in the 2B subclone. Thus, catecholamine refractoriness cannot be attributed to induction of phosphodiesterase. This implies that induction of a protein or proteins, important in catecholamine refractoriness, affects the synthesis rather than the degradation of cyclic AMP.     

Cyclic adenosine 3',5'-monophosphate during glucose repression in the rat liver

Intragastric administration of glucose inhibits the induction of serine dehydratase and tyrosine aminotransferase by glucagon in rat liver, but has no effect on the increase in hepatic adenosine 3',5'-monophosphate resulting from administration of glucagon. Thus, glucose repression in mammalian liver, unlike catabolite repression in microorganisms, appears to operate independently of the amounts of cyclic nucleotide in the cells.     

诺卜醇及其新型四员环类化合物的合成分析

综述了由β－蒎烯合成诺卜醇及诺卜醇衍生物合成的研究状况，分析了由诺卜醇及其衍生物合成新型四员环类化合物的可行性，并对几种合成方法进行了探讨。     

Platelet-derived serotonin mediates liver regeneration

The liver can regenerate its volume after major tissue loss. In a mouse model of liver regeneration, thrombocytopenia, or impaired platelet activity resulted in the failure to initiate cellular proliferation in the liver. Platelets are major carriers of serotonin in the blood. In thrombocytopenic mice, a serotonin agonist reconstituted liver proliferation. The expression of 5-HT2A and 2B subtype serotonin receptors in the liver increased after hepatectomy. Antagonists of 5-HT2A and 2B receptors inhibited liver regeneration. Liver regeneration was also blunted in mice lacking tryptophan hydroxylase 1, which is the rate-limiting enzyme for the synthesis of peripheral serotonin. This failure of regeneration was rescued by reloading serotonin-free platelets with a serotonin precursor molecule. These results suggest that platelet-derived serotonin is involved in the initiation of liver regeneration.     

2,3-二甲氧基-5-甲基苯酚衍生物的合成及生物活性

以2-羟基-5-甲基苯乙酮为原料,经溴化、甲醚化、Baeyer-Villiger氧化、醇解、Ullman反应得到具有杀虫活性的苦皮藤内生菌代谢产物2,3-二甲氧基-5-甲基苯酚。以对甲酚为原料,经溴化、Ullman反应和甲醚化反应得到3,4,5-三甲氧基甲苯,所合成化合物结构经核磁共振确认。测定了这些化合物对3龄粘虫（My-thimna separataWalker）幼虫的毒杀活性和对某些植物病原菌的抑菌活性。其中部分化合物在500 mg/kg的浓度下有较强的抑菌活性。     

抗四（4—三甲胺苯）卟啉抗体的酶学性质研究

制备了抗四 (4 三甲胺苯 )卟啉的单克隆抗体细胞株 3B6 ,测得了抗原 -抗体解离常数 (用ELISA法测定 )为 4 6 4× 10 -5;单抗 3B6为IgG2b ;抗体酶 3B6Km=33 0 0mmol/L ,Kcat=12 2 0 0min-1,说明该抗体酶是一种很好的新的生物催化剂     

Harderian gland: development and influence of early hormonal treatment on porphyrin content

The porphyrin content of the rat Harderian gland remains low until 12 days of age at which time both porphyrin content and concentration rapidly increase. Intraperitoneal administration of tetraiodothyronine (thyroxine) into newborn animals advances the appearance of porphyrin in the gland. Conversely, a single injection of cortisol acetate into newborns retards the appearance of porphyrin. The time of porphyrin appearance in the gland parallels the time for maturation of the evoked cortical response to visual stimulation in normal and hormone-treated animals.     

微波辐射下NH4Ac催化合成5-亚苄基绕丹宁乙酸衍生物

在微波辐射条件下,以NH4Ac为催化剂,芳香醛与3-羧甲基绕丹宁发生Knoevenagel缩合反应,以76%~93%的产率制备了一系列5-亚苄基绕丹宁乙酸衍生物,产物结构经1H NMR和IR确证。     

固醇调节元件结合蛋白-1c在肝脂肪合成中转录调节

固醇调节元件结合蛋白 -1c(SREBP -1c)是脂肪合成基因的重要转录调节因子 ,又称脂肪细胞决定和分化因子 1(AdipocyteDetermi nationandDifferentiationfactor -1,ADD1) ,它是动物肝脏中主要的转录物 ,主要调节动物脂肪合成和葡萄糖代谢相关基因的表达。研究发现 ,SREBP -1c的过度表达与肝脏等非脂肪组织的脂质积聚相关。SREBP -1c调节体内的脂肪合成主要是通过改变自身的mRNA水平来实现的 ,即生脂酶的转录调节是由SREBP- 1cmRNA的数量控制的。另一方面 ,LXRs、胰岛素、胰高血糖素等因素对SREBP- 1c的转录有调节作用。     

Macroscopic hierarchical surface patterning of porphyrin trimers via self-assembly and dewetting

The use of bottom-up approaches to construct patterned surfaces for technological applications is appealing, but to date is applicable to only relatively small areas (approximately 10 square micrometers). We constructed highly periodic patterns at macroscopic length scales, in the range of square millimeters, by combining self-assembly of disk-like porphyrin dyes with physical dewetting phenomena. The patterns consisted of equidistant 5-nanometer-wide lines spaced 0.5 to 1 micrometers apart, forming single porphyrin stacks containing millions of molecules, and were formed spontaneously upon drop-casting a solution of the molecules onto a mica surface. On glass, thicker lines are formed, which can be used to align liquid crystals in large domains of square millimeter size.     

具有农药活性的姜黄素类化合物研究进展

综述了近年来具有良好农药活性的姜黄素类化合物的合成及生物活性研究进展,并对该类化合物在农药开发方面的应用前景进行了展望,为其在农药中的应用提供了借鉴。