PHYSICAL CHEMICAL STUDIES ON THE SPECIFIC INTERACTION OF AN ACRIFLAVINE-PHOSPHOTUNGSTIC ACID COMPLEX WITH DOUBLE-STRANDED NUCLEIC ACIDS

The detailed definition of the structure of DNA in chromosomes and in interphase chromatin is important for correlating the structure of the genetic material with various states of physiological activity. A general approach to developing specific reagents for a variety of such studies in solution and in tissues is to combine a chemically specific organic cation with the electron-opaque phosphotungstic acid (PTA) molecule. The reagent described in this paper was made from the interaction of acriflavine and phosphotungstic acid. The acriflavine-PTA complex (a) displays some unique absorption and fluorescence properties, (b) binds specifically to DNA and RNA by intercalation of the acriflavine moiety, and (c) is electron opaque. In addition, it binds to double-stranded synthetic polynucleotides, but not to a variety of proteins, nucleoproteins, or polysaccharides.     

光周期对三带喙库蚊发育期间体内核酸动态的影响

作者测试了长短光周期处理的三带喙库蚊Culex tritaeniornynchus(Giles)各虫态与滞育及解滞蚊体内RNA与DNA的变化.结果表明:幼虫与蛹核酸含量最高,成虫期变化比较稳定.短光周期可以降低该蚊发育期间核酸的合成作用.雌蚊卵形成期间DNA相对稳定,吸血后卵巢开始发育,RNA含量明显增加,36—48小时达到高峰,然后逐渐下降.10—15日龄的滞育蚊体内DNA比发育蚊低,解滞蚊RNA与DNA含量均比发育蚊为高.新蚊、发育、滞育与解滞蚊间DNA、RNA含量不同,DNA、RNA减少与增加可用作判断滞育发生与解除的一个生化指标.     

核酸序列重复片段的统计分析

对核酸序列编码区的重复片段进行了统计分析。发现不同物种的序列具有近似相等的约化重复长度和次数,研究了重复区内碱基分布的特点,并讨论了此结果可能的生物学涵义。     

KINETICS OF THE SODIUM-DEPENDENT TRANSPORT OF GAMMA-AMINOBUTYRIC ACID BY SYNAPTOSOMES

The kinetics of transport of gamma-aminobutyric acid [2,3-³H] by synaptosomes from rat brain was studied by means of a rapid filtration technique. The rate of uptake was proportional to the protein concentration over the range 0.05—0.2 mg of synaptosomal protein per ml. Although apparent allosteric kinetics were observed with sodium, transport followed simple saturation kinetics with respect to GABA and no heterotropic, cooperative effects of GABA on sodium on kinetics were observed. A minimum of three interacting sodium sites is suggested the basis of Hill plots of the sodium data. Both the apparent K_m and V_max for GABA were functions of the sodium ion concentration but the effect of sodium was considerably greater on V_max than on the apparent K_m The V_max for GABA was 1.1 ± 0.5 nmol.min^?1 mg^?1 of protein at 95 mm sodium and decreased to 12 per Cent of this value at 19 mm sodium. The apparent K^m for GABA increased from 4.0 ± 1.0 μm at 95 mm sodium to 8.4 ± 2.0 μm at 19 mm sodium. Potassium was a noncompetitive inhibitor with respect to GABA and did not affect the apparent cooperativity observed with sodium. These findings are discussed in terms of models of GABA transport.     

THE BIOCHEMICAL ROLE OF NATURALLY OCCURRING POLYAMINES IN NUCLEIC ACID SYNTHESIS

1. The polyamines, putrescine, spermidine and spermine occur in free or acetylated form in a wide variety of living organisms. Putrescine is biosynthesized from ornithine or arginine; spermidine and spermine from methionine and either ornithine or arginine. 2. It is difficult to determine the intracellular distribution of polyamines since they are all very soluble in water and they are readily redistributed when cells are disrupted. Evidence suggests that a substantial proportion of the intracellular polyamines is attached to the ribosomes and that spermidine is not concentrated in the nucleus. 3. Polyamines bind strongly to both DNA and RNA. The strength of binding is:spermine > spermidine > putrescine. Polyamines stabilize the double helix of DNA, probably by forming a bridge across the narrow groove, by involving electrostatic bonding with the phosphate group. However, they do not appear to alter the overall conformation of DNA. Spermine enables single-stranded RNA to fold into a more compact configuration which is less susceptible to attack by ribonuclease. 4. Spermine and spermidine are able to stimulate the DNA primed RNA polymerase. They facilitate the removal of RNA from the DNA-RNA-enzyme complex. 5. Polyamines promote the association of ribosomal subunits and also the binding of amino acyl transfer RNA to ribosomes. They cause increased coding ambiguities in the process of translation in certain bacterial systems. 6. There is a close correlation between the intracellular concentration of spermidine and the rate of RNA synthesis both in rat liver and in Escherichia coli. Conditions which affect the rate of RNA synthesis also affect the concentration of free intracellular spermidine. 7. Bacteria usually contain putrescine and spermidine, whereas animal tissues contain spermine and spermidine. Spermidine probably fulfils the same role in both bacteria and animal tissues, but the presence of spermine, which is common to eucaryotes, is possibly associated with their more complex mechanisms for regulating RNA and protein synthesis.     

ENZYMES OF NUCLEIC ACID METABOLISM IN THE BRAINS OF YOUNG AND ADULT RATS

A number of precursors of RNA are incorporated several-fold more readily into the RNA of brain slices from 10-day-old rats than into RNA of slices from adult animals. The brains of the young animals show moderately higher levels of some of the anabolic enzymes of RNA metabolism including RNA polymerase (nucleosidetriphosphate: RNA nucleotidyltransferase; EC 2.7.7.6) and substantially lower levels of the degradative enzymes, the nucleoside phosphorylases. The data suggest that all the enzymes work in a concerted fashion to produce an increased rate of synthesis in young animals rather than that any single controlling enzymic event is responsible.     

THE THERAPEUTIC INDEX OF CHEMOTHERAPEUTIC AGENTS: THE EFFECT OF NUCLEIC ACID ON DIMIDIUM BROMIDE

SUMMARY: The complexes of dimidium bromide with nucleic acids are less toxic and bactericidal than dimidium bromide itself, but the toxicity is reduced more than the antibacterial activity. The therapeutic activity is, therefore, raised.     

ROLE OF NUCLEIC ACID AND PROTEIN METABOLISM IN THE INITIATION OF GROWTH AT GERMINATION

When dry decotyledonized embryos of Raphanus are supplied withwater, a brief period of water absorption (phase A) is followedby a period of no fresh weight increase (phase B) which lastsfor 8 hr at 30°. In this period, embryos become ready toadvance into the period of fresh weight increase (phase C). When embryos were exposed to various concentrations of thiouracilor actinomycin D solution from 0 hr of water supply, increasesin fresh weight and in RNA content measured at 13 hr were inhibitedin parallel with each other. Chloramphenicol and puromycin inhibitedthe fresh weight increase without affecting the RNA increase.When embryos were exposed to thiouracil or puromycin for 2,4 and 6 hr, beginning at 0 hr of water supply, the start ofphase C delayed 2, 4 and 6 hr, respectively. When these drugswere given after phase B had progressed at least for 2 hr, thedelay of the start of phase C was shorter than the period ofthe drug treatment. If given at the end of phase B, thiouraciland actinomycin D inhibited the incorporation of ¹⁴C-uracilbut not the fresh weight increase, while chloramphenicol andpuromycin inhibited the latter without inhibiting the former. During phase B, protein content per dry weight of embryo didnot increase, but the rate of ¹⁴C-leucine incorporation increasedremarkably to reach the level in phase C. Incorporation of labeledleucine was inhibited if embryos were subjected to thiouracilor actinomycin D action during phase B, but not if the drugswere given when phase B had been completed. Puromycin and chloramphenicolinhibited the incorporation whenever they were given. The increase in respiratory activity during phase B was inhibitedrelatively little by the above mentioned four drugs. In conclusion syntheses of RNA and protein seem to be essentialfor the progress of phases B and C, protein synthesis havinga more direct effect. (Received September 17, 1965; )     

INTERRELATIONS BETWEEN POLYAMINES AND NUCLEIC ACIDS: CHANGES OF POLYAMINE AND NUCLEIC ACID CONCENTRATIONS IN THE DEVELOPING RAT BRAIN

The rat brain concentrations of protein, RNA, DNA, putrescine, and of the polyamines spermidine and spermine, were studied during development. Putrescine formation is apparently controlled by ornithine decarboxylase. Spermidine and spermine concentrations change in inverse directions to their anabolic enzymes. It has been presumed, therefore, that the low concentrations of the polyamine-synthesizing enzymes in immature brain are compensated for, by high putrescine and S-adenosylmethionine concentrations. In agreement with previous findings for fish brain, the changes in RNA and spermidine concentrations were most closely correlated. The functions of DNA: spermine are directly correlated only during the periods of brain maturation, after cell proliferation has nearly ceased.     

家蚕后丝腺亚细胞组分中核酸和蛋白质的分布

丝心蛋白是家蚕后丝腺的分泌产物。在家蚕五龄早期,后丝腺细胞中迅速形成丝心蛋白合成所必需的一些亚细胞结构,在后丝腺细胞质中粗糙内质网迅速增多,平滑内质网迅速形成空泡状或管状。而且生化测定表明,在五岭早期后丝腺中DNA,RNA、蛋白质和脂肪的含量皆迅速增加,这些为在五龄后期丝心院的合成,即为丝心蛋白信息的转录和翻译,提供亚细胞结构和生化代谢的物质基础(Tashiro等1968;赤井弘1973)。因此有必要对家蚕后丝腺亚细胞组分如细胞核、线粒休、微粒体和105,000g上清液中核酸和蛋白质代谢进行研究。本文初步建立一种分离家蚕后丝腺亚细胞组分的差级离心方法,并测定各亚细胞组分中核酸和蛋白质的含量。     

昆虫核酸分子系统学研究进展

本文从研究对象、方法、类群、内容等方面综述了近十年来昆虫核酸分子系统学研究进展概况。文中首先介绍了ＲＦＬＰＡ、探针杂交及ＤＮＡ指纹、ＰＣＲ与ＲＡＰＤ－ＰＣＲ、顺序分析方法及应用情况,列举了在双翅目、膜翅目、同翅目、直翅目等目昆虫中的研究进展,并从居群遗传结构、分类学研究、系统发育和分子进化４个方面总结了昆虫核酸分子系统学的研究内容和主要成果,最后指出ＲＡＰＤ－ＰＣＲ与ＲＦＬＰ联合用于测序是近期昆虫分子系统学上最有应用价值的方法。     

KINETICS OF COMPETITIVE INHIBITION OF NEUTRAL AMINO ACID TRANSPORT ACROSS THE BLOOD-BRAIN BARRIER

The transport of tryptophan across the blood-brain barrier is used as a specific example of a general approach by which rates of amino acid influx into brain may be predicted from existing concentrations of amino acids in plasma. The kinetics of inhibition of [¹⁴C]tryptophan transport by four natural neutral amino acids (phenylalanine, leucine, methionine, and valine) and one synthetic amino acid (α-methyl tyrosine) is studied with a tissue-sampling, single injection technique in the barbiturate-anesthetized rat. The equality of the K₁ (determined from cross-inhibition studies) and the K_m (determined from auto-inhibition data) for neutral amino acid transport indicate that these amino acids compete for a single transport site in accordance with the kinetics of competitive inhibition. Based on equations derived for competitive inhibition, apparent K_m values are computed for the essential neutral amino acids from known data on amino acid transport K_m and plasma concentrations. The apparent K_m values make possible predictions of the in vivo rates of amino acid influx into brain based on given plasma amino acid concentrations. Finally, a method is presented for determining transport constants from saturation data obtained with single injection techniques.     

THE KINETICS OF THE REACTION WHICH TAKES PLACE BETWEEN IODOACETIC ACID AND GLYCINE

1. The kinetics of the reaction which takes place between glycine and iodoacetic acid was studied by means of the polarographic method. 2. On the basis of kinetic equations, evidence was obtained that (a) The reaction proceeds in two steps in which the hydrogens of the amino group are consecutively replaced by the acetyl radicals, the velocity constants being in the ratio 2:1. (b) Only the anionic form of glycine is able to react since the velocity constants at any pH are proportional to the concentration of glycine anion. (c) The reaction is of the ionic type, showing a positive salt catalysis, which, according to Brönsted''s hypothesis, involves the primary and the secondary salt effects. 3. The fact that only the glycine anion is able to react was explained as being due to the existence of an unbonded pair of electrons on the nitrogen in the NH₂ group. The NH₃ ⁺ group, however, in which these electrons are shared by H⁺, must, therefore, be inactive.     

激光所致核酸损伤的分子机制

本文综述了近来有关紫外激光诱导核酸损伤(主要是碱基损伤、单链断裂和双链断裂)形成的化学过程的文献报导,主要是讨论了双光子激发核酸碱基,致使核酸产生单链断裂和双链断裂的光致电离过程,以及由此归纳出来的激光诱导核酸链断裂的化学模型     

TOPOCHEMICAL ASPECTS OF NUCLEIC ACID AND PROTEIN METABOLISM WITHIN THE NEURON-NEUROGLIA UNIT OF THE SPINAL CORD ANTERIOR HORN

Abstract— Using a two-wavelength modification of ultraviolet and visible cytospectro-photometric methods, the content of nucleic acids per cell was determined in neuronal cytoplasm and glial satellite cell-bodies from the spinal cord anterior horns in mice and rats. Mice which had been swimming for 3 and 4 h showed an increase in the content of RNA in the spinal motoneurons with no changes in the neuroglia. Stronger stimulation of the nervous system such as electrical skin irritation (20-40 V, approx. 40 impulses/min) for 5 min resulted in an increase of RNA in the motoneurons of rat spinal cord and a decrease in the surrounding glia. Exhausting actions upon the nervous system (60 min irritation of rat paws by the electrical current, acute clonic convulsions in rats injected with cardiazol (pentamethylenetetrazol, metrazol) or initial free motor activity after 3 weeks of restraint of mice) induced a marked decrease of RNA content throughout the whole neuron-neuroglia unit. After stimulation, return to normal amounts of RNA and protein was more rapid in glia than in neurons. After 1-3 days rest the level of RNA was normal in motoneurons, but a decrease in glial RNA was shown. These trace changes in the glia are believed to reflect an adaptation mechanism in the nervous system at the cellular level. The relationship between neuronal and glial compartments within the neuron-neuroglia unit is discussed; a supporting, homeostatic, secondary role of glial metabolism with respect to adequate reconstruction of neuronal metabolism is outlined.     

ADAPTATION OF NUCLEIC ACID EXTRACTION METHODS FOR ANIMAL FEEDS

Animal feeds contain a wide variety of microorganisms that may cause animal and human health problems. It would be desirable to rapidly detect as many of these organisms as possible. The objective of this study was the evaluation of nucleic acid extraction protocols to determine an optimal sample processing strategy for DNA isolation from different animal feeds. DNA extraction methods were applied to selected animal feeds to determine which could consistently provide DNA visible by gel electrophoresis. Comparable recovery of DNA extraction protocols was achieved after 20 g of each feed samples were mixed with 0.2% peptone containing 0.01% Triton X-100. For 9 different feeds visible DNA could be consistently detected for each feed indicating that a detergent-based dilution step prior to DNA extraction recovered sufficient DNA regardless of the feed matrix.