Pineal gland: dibutyryl cyclic adenosine monophosphate stimulation of labeled melatonin production

In organ cultures of intact rat pineal glands, N(6)O(2')-dibutyryl adenosine 3', 5'-monophosphate stimulates the conversion of tritiated trytophan to tritiated melatonin, as does L-norepinephrine. Potential sites of stimulation of melatonin production by dibutyryl cyclic adenosine monophosphate are discussed, based on observations that the dibutyryl analog also stimulates the conversion of serotonin labeled with carbon-14 to carbon-14-labeled melatonin without altering hydroxyin-dole-O-methyl transferase activity or intracellular accumulation of serotonin labeled with carbon-14.     

Crystal and molecular structure of adenosine 3',5'-cyclic phosphate

The structure of adenosine 3',5'-cyclic phosphate has been determined by single-crystal x-ray diffraction. The two molecules in the asymmetric unit show different conformation about the glycosidic bond, while other structural details are essentially the same. The furanose rings are puckered with the C(4') atom out of the best four-atom plane. The bond lengths and angles appear to be normal.     

Cytidylic acid "a" trihydrate: structure and conformation

Cytidylic acid "a" (cytidine 2'-monophosphate) crystallizes in the triclinic space group P1 with two molecules of cytidine monophosphate (C(9)H(14)O(8)N(3)P) and six molecules of water in the unit cell. X-ray analysis of this crystal shows that in both molecules, the base is in the anti conformation, the ribose ring is C(2')-endo puckered, and the hydroxyl O(5') is gauche-gauche. The two molecules are linked by a short hydrogen bond through the phosphate oxygens.     

生物素标记犬瘟热病毒DNA探针的制备与纯化

用以选择犬瘟热病毒ＲＮＡ的有关碱基顺序，设计ＤＮＡ探针，并在５＇末端偶关一个氨基连接分子：５×ＡＧＧＧＣＴＣＡ－ＧＧＴＡＧＴＣＣＡＧＣＡＡＴＧ３＇，共２３个碱基和一个氨基连接分子。ＮＨ２－ＤＮＡ探针在ＤＮＡ合成仪上合成。合成产物同生物素酰氨基已酸盐Ｎ－羟琥珀酰亚胺酯反应，反应物经高效硅胶薄层板纯化，得到生物素标记犬温热病毒ＤＮＡ探针。     

Genetic and somatic effects of carbon-14

On the basis of information about carbon-14 given by Libby, calculations are made of the predicted genetic and somatic effects of the carbon-14 produced by the testing of nuclear weapons. It is concluded that 1 year of testing (30 megatons of fission plus fusion) is expected to cause in the world (stimated future number of births per year 5 times the present number) an estimated total of about 55,000 children with gross physical or mental defects, 170,000 stillbirths and childhood deaths, and 425,000 embryonic and neonatal deaths. (There is an unknown amount of overlap of these three categories.) These numbers are about 17 times the numbers usually estimated as the probable effects of the fallout fission products from 1 year of testing. In addition, the somatic effects of bomb-test carbon-14 are expected to be about equal to those of fission products, including strontium-90, with respect to leukemia and bone cancer and greater than those of fission products with respect to diseases resulting from radiation damage to tissues other than bone tissue and bone marrow. All of the estimated numbers are subject to great uncertainty; they may be as much as 5 times too high or 5 times too low. The uncertainty in the estimation of the relative effects of carbon-14 and fission products in world-wide fallout is not so great.     

Structure of a dinucleotide: thymidylyl-(5'-3')-thymidylate-5' (pTpT)

The crystal and molecular structure of the naturally occurring deoxyribose dinucleotide sodium thymidylyl-(5'-->3')-thymidylate-5' has been determined by x-ray diffraction. There are four molecules of dinucleotide and 52 water molecules in an orthorhombic unit cell of dimensions (in angstroms) a = 16.06, b = 15.13, c = 15.65, space group P2(1)2(1)2. There is a very high degree of conformational consistency between the two halves of the molecule when the dinucleotide is viewed as the combination of two 5'-mononucleotides. The planes of the two thymines are not parallel, but are tilted 38 degrees with respect to each other. An extensive system of hydrogen bonding exists involving the bases, waters, phosphates, and sodiums; no base-base hydrogen bonding occurs. The dinucleotide structural parameters should be of assistance in interpreting DNA fiber diagrams in terms of possible structures.     

Thyroxine: convesion to triiodothyronine by isolated perfused rat heart

Thyroxine labeled with carbon-14 and iodine-125 was perfused through surviving rat hearts. Only when unlabeled triiodothyronine was added as a carrier could the newly formed doubly labeled triiodothyronine be isolated. The fact that this triiodothyronine was labeled with the correct ratio of carbon-14 to iodine-125 indicated that it originated from thyroxine. Approximately 5 percent of the initial carbon-14 radioactivity was found in the recovered triiodothyronine.     

ISSR分子标记技术及其在园艺作物中的应用

ISSR是一种基于微卫星序列发展起来的新的分子标记,具有简便迅速、稳定高效、DNA多态性高等优点。ISSR标记呈孟德尔式遗传,大部分ISSR标记为显性标记。ISSR技术的基本原理是在SSR的3’或5’端加锚1~4个嘌呤或嘧啶碱基,引起特定位点退火,使引物与匹配SSR的一端结合,从而对基因组中特定片段进行扩增、检测,最后根据谱带的有无及相对位置分析不同样品间ISSR标记的多态性。目前ISSR分子标记技术在园艺作物的遗传多样性研究、遗传图谱构建、基因定位、分子标记辅助育种及品种纯度鉴定方面得到了广泛应用,但ISSR技术在解决交配系统、计算杂合度与父系分析等问题上效果不佳,今后仍需结合研究目的选择适宜的分子标记进行研究,以提高分子标记的选择效率。     

A gradient of sequence divergence in the human adult alpha-globin duplication units

The nucleotide sequences of the two 5'-homology blocks of human alpha-globin gene duplication units were determined. The sequence difference between the two blocks is essentially zero in the 5' portions, and increases gradually toward the 3' ends until it reaches a value of 18 percent. This gradient of sequence divergence is similar to the distribution of the frequencies of gene conversion along several loci in Ascobolus and yeast. Hot spots for initiation of gene correction processes appear to exist near the 5' ends of the human alpha-globin duplication units. The data provide the physical evidence for polar gene correction process in a mammalian genome.     

Interstellar carbon in meteorites

The Murchison and Allende chondrites contain up to 5 parts per million carbon that is enriched in carbon-13 by up to + 1100 per mil (the ratio of carbon-12 to carbon-13 is approximately 42, compared to 88 to 93 for terrestrial carbon). This "heavy" carbon is associated with neon-22 and with anomalous krypton and xenon showing the signature of the s-process (neutron capture on a slow time scale). It apparently represents interstellar grains ejected from late-type stars. A second anomalous xenon component ("CCFXe") is associated with a distinctive, light carbon (depleted in carbon-13 by 38 per mil), which, however, falls within the terrestrial range and hence may be of either local or exotic origin.     

Man-made carbon-14 in deep Pacific waters: transport by biological skeletal material

Calcareous particles present in Pacific waters at depths of 50 to 3500 meters were collected by filtering seawater through spongin matrix. The specific activity of carbon-14 could be measured in two of these collections from depths of 2300 and 3500 meters. The ratios of carbon-14 to carbon-12 correspond to values observed in surface waters in recent years as a result of the addition of manmade carbon-14, thus indicating that the calcareous particles resulted from recent biological productivity. The results are related to the mean settling rates and the sizes and dissolution rates of biogenic calcareous particles in transit through a seawater column.     

Banded corals: changes in oceanic carbon-14 during the little ice age

Radiocarbon analyses and stable isotope measurements are presented foro recent cores of banded corals from the Florida Straits. These values provide a record of variations in the ratio of carbon-14 to carbon-12 in the dissolved inorganic carbon in the surface waters of the Gulf Stream from A.D. 1642 to 1800. An increase in the carbon-14/carbon-12 ratio of 7 per mil for coral growth during the early 1700's was most likely induced by an increase in the carbon-14/carbon-12 ratio of 20 per mil in the atmospheric carbon dioxide that occurred at about 1700. The ratios of oxygen 18 to oxygen-16 in these coral bands show a small decrease of a water temperature ( approximately 1 degrees C) during the latter part of the Little Ice Age (1700 to 1725). These results support the hypothesis that the increase in atmospheric carbon-14 at about 1700, and possibly the temperature change as well, was caused by a decrease in solar activity (Maunder sunspot minimum).     

Oxidation of graphitic carbon in certain soils

Artificial graphitic carbon-14 was oxidized to carbon-14 dioxide in the presence of certain nonsterile soils. Treatment of these soils for the inhibition of biologic activity, by several methods including 5 megarads of electron-beam irradiation, yielded much-less-reactive systems in the oxidation of carbon. Intervention of a biologic agent in some of these oxidative processes is suggested.     

H9N2亚型AIV NA基因多聚腺苷酸化信号位点对病毒复制的影响

H9N2亚型禽流感病毒NA基因vRNA 5′端的多聚腺苷酸化信号位点具有多样性,突变发生时,该位点失去与聚合酶的结合能力或结合能力减弱,阻碍多聚腺苷酸化过程,影响病毒mRNA的转录过程。为探究H9N2亚型禽流感病毒NA基因5′端多聚腺苷酸化信号位点处5个或6个连续的尿嘧啶(U₅或U₆)碱基对病毒生物学特性的影响,以一株四川分离株A/Chicken/China/Sichuan/CQY/2014(H9N2)为骨架的反向遗传系统构建突变株。结果显示,含U₅的H9N2突变株(rCQYU₅-H9N2)的血凝效价、TCID₅₀和EID₅₀滴度均高于含U₅的H9N2突变株(rCQYU6-H9N2),但生长曲线无显著差异,表明H9N2 NA基因5′端多聚腺苷酸化信号位点U₅或U₆结构均不影响病毒的拯救,但U₅有助于提高病毒在鸡胚与细胞中的复制滴度。本实验研究结果可为H9N2亚型禽流感病...     

Carbon isotopic evidence for different feeding patterns in two hyrax species occupying the same habitat

The carbon-13/carbon-12 ratios of the carbonate and collagen fractions of bone of the sympatric hyrax species Procavia johnstoni and Heterohyrax brucei indicate that the former obtains most of its diet by grazing while the latter is primarily a browser. The carbon-13/carbon-12 ratios of these fractions in fossil bone will record information about diet if they have not been altered during diagenesis.     

Atmospheric radiocarbon calibration to 45,000 yr B.P.: late glacial fluctuations and cosmogenic isotope production

More than 250 carbon-14 accelerator mass spectrometry dates of terrestrial macrofossils from annually laminated sediments from Lake Suigetsu (Japan) provide a first atmospheric calibration for almost the total range of the radiocarbon method (45,000 years before the present). The results confirm the (recently revised) floating German pine chronology and are consistent with data from European and marine varved sediments, and combined uranium-thorium and carbon-14 dating of corals up to the Last Glacial Maximum. The data during the Glacial show large fluctuations in the atmospheric carbon-14 content, related to changes in global environment and in cosmogenic isotope production.     

Carbon-14 and tritium measurement by means of bremsstrahlung emissions

The feasibility of measuring carbon-14 and tritium in vivo has been demonstrated in the rat; thin scintillation detectors were used for the measurement of bremsstrahlung produced by these soft beta emitters. Measurements of tritium in vivo are limited to the study of surface phenomena, whereas bremsstrahlung produced by carbon-14 may be detected from depths of several centimeters.     

Carbon-13/carbon-12 ratio is relatively uniform among honeys

The variability of the carbon-13/carbon-12 ratio in honeys was evaluated preliminary to use of the ratio to detect the addition of high-fructose corn syrup to honey. Eighty-four honey samples representing 34 states and including 37 floral types from 17 plant families were analyzed. The mean value of the per mil increment in carbon-13 (delta13C) for all samples is -25.2 per mil, and the coefficient of variation is 3.7 percent. This is the smallest variation yet encountered for a honey constituent or physical property. The range and magnitude of the values suggest that the floral sources are C(3) plants.     

Carbon-13 and carbon-14 abundances in alaskan aquatic organisms: delayed production from peat in arctic food webs

Inputs of terrestrial peat carbon to the nearshore Alaskan Beaufort Sea from erosion and fluvial transport are of the same magnitude as in situ primary production within 10 kilometers of shore. Nevertheless, carbon-13/carbon-12 ratios and carbon-14 abundances in marine organisms show that only small amounts of the terrestrial carbon are transferred beyond the microbial level. Freshwater organisms, however, are heavily dependent on peat, as shown by pronounced seasonal radiocarbon depressions in resident fish and ducks. Tundra ponds and lakes are areas where accumulated terrestrial peat carbon is apparently transferred to aquatic insect larvae and passed on to higher organisms. The lack of functionally analogous abundant marine prey organisms may explain why peat carbon is not efficiently transferred to apical food web species in the marine environment.     

Synchronous radiocarbon and climate shifts during the last deglaciation

Radiocarbon data from the Cariaco Basin provide calibration of the carbon-14 time scale across the period of deglaciation (15,000 to 10, 000 years ago) with resolution available previously only from Holocene tree rings. Reconstructed changes in atmospheric carbon-14 are larger than previously thought, with the largest change occurring simultaneously with the sudden climatic cooling of the Younger Dryas event. Carbon-14 and published beryllium-10 data together suggest that concurrent climate and carbon-14 changes were predominantly the result of abrupt shifts in deep ocean ventilation.