中国下泥盆统脊椎动物化石组合层序

本文综合了滇、黔、川、桂等地的一些早泥盆世地层剖面中的脊椎动物化石的出露情况,粗略地描绘出了早期脊椎动物演化的一般特征,归纳成三个发展阶段。并以此为依据,讨论了下泥盆统的分层与对比。     

大气氟污染对达乌尔黄鼠及其环境的影响

本文研究大气氟污染对达乌尔黄鼠及其环境的影响。研究区内的钢厂为大气氟污染的点源。在研究区内选6个取样点,分别取黄鼠大腿骨骨样、植物样和土样。 黄鼠大腿骨骨灰、植物和土壤的含氟量是随与污染源的距离和方向的不同而变化的,离污染源愈远各样品的含氟量愈低。污染源西北方向,靠近污染源的取样点污染特别严重。但是,黄鼠体重与其大腿骨骨灰含氟量间没有明显相关。黄鼠可认为是对氟污染的“耐干扰种”。 在研究区内,氟污染对植物群落的种类、生物量和群落的多样性没有明显地影响。大腿骨骨灰和植物含氟量间存在一定的回归关系,其关系式为Y=27.16X~1.02。     

Identification, characterization, and quantitative measurement of cyclic AMP receptor proteins in cytosol of various tissues using a photoaffinity ligand.

Two protein bands, present in cytosol fractions from each of seven rat tissues examined, specifically incorporated 32P-labeled 8-azidoadenosine 3':5'-monophosphate (8-N3-[32P]cAMP), a photoaffinity label for cAMP-binding sites. These proteins had apparent molecular weights of 47,000 and 54,000 on a sodium dodecyl sulfate-polyacrylamide gel electrophoresis system. These two proteins were characterized in three of the tissues, namely, heart, uterus, and liver, by the total amount of 8-N3-[32P]cAMP incorporation, by the dissociation constant (Kd) for 8-N3-[32P]cAMP, and by the nucleotide specific inhibition of 8-N3-[32P]cAMP incorporation. Several lines of evidence were obtained that the protein with an apparent molecular weight of 47,000 represents the regulatory subunit of a type I cAMP-dependent protein kinase, while the protein with an apparent molecular weight of 54,000 represents the regulatory subunit of a type II cAMP-dependent protein kinase. Almost all of the cAMP receptor protein found in the cytosol of these tissues, as measured by 8-N3-[32P]cAMP incorporation, was associated with these two protein kinases, in agreement with the idea that most effects of cAMP are mediated through protein kinases. The photoaffinity labeling with 8-N3-[32P]cAMP can be used to estimate quantitatively the amounts of regulatory subunit of type I and type II cAMP-dependent protein kinases in various tissues.     

Yeast mutants deficient in heme biosynthesis and a heme mutant additionally blocked in cyclization of 2,3-oxidosqualene.

Mutants of Saccharomyces cerevisiae were isolated which were blocked in heme biosynthesis and required heme for growth on a nonfermentable carbon source. They were rho+, and grew fermentatively on ergosterol or cholesterol and Tween 80, as a source of oleic acid. Cells grown on ergosterol and Tween 80 lacked cytochromes and catalase which were restored by growth on heme. The mutants comprised five nonoverlapping complementation groups. Tetrad analysis showed that the pleiotropic properties of each of the mutants resulted from a single mutation in one of five unlinked loci (hem1 to hem5) affecting heme biosynthesis. Biochemical studies confirmed that each mutation resulted in loss of a single enzyme activity. hem1 mutants grew on delta-aminolevulinate and lacked delta-aminolevulinate synthase activity, hem2 mutants lacked delta-aminolevulinate dehydratase, and hem3 mutants uroporphyrin I synthase. Mutants in hem1, hem2, and hem3 had an additional requirement for methionine on synthetic medium supplemented with either heme or ergosterol and Tween 80, owing to a lack of sulfite reductase which contains siroheme, a modified uroporphyrin III. Since hem4 and hem5 mutants have sulfite reductase activity under all growth conditions, they are blocked after uroporphyrin III. Cell extracts of a hem4 mutant incubated with delta-aminolevulinate accumulated coproporphyrin III suggesting a block in coproporphyrinogenase, the enzyme which converts coproporphyrinogen III to protoporphyrinogen. Cells and extracts of a hem5 mutant accumulated protoporphyrin IX. Since it was the only mutant that grew on heme but not on protoporphyrin IX, a block in ferrochelatase was suggested for this strain. Mutant strains grown on heme had the sterol composition of wild type cells, whereas without heme only squalene, small amounts of lanosterol, and added sterol was observed. A heme product therefore participates in the transformation of lanosterol to ergosterol. A hem3 mutant was isolated which was also blocked between 2,3-oxidosqualene and lanosterol (erg12). When grown on lanosterol or ergosterol (with Tween 80) it accumulated a compound which was identified as 2,3-oxidosqualene by comparison with the synthetic compound in thin layer and gas-liquid chromatography, and by proton magnetic resonance and mass spectroscopy. Supplementation with heme did not remove the requirement for sterol, but it enabled the mutant to convert lanosterol to ergosterol.     

Flavonoids from Artemisia ludoviciana var. ludoviciana

Nineteen flavonoids were isolated from Artemisia ludoviciana var. ludoviciana, including a new 2′- hydroxy- 6-methoxyflavone, 5,7,2′,4′-tetrahydroxy-6,5′-dimethoxyflavone. The known compounds include quercetagetin 3,6,3′,4′-tetramethyl ether, eupatilin, 5,7-dihydroxy-3,6,8,4′-tetramethoxyflavone, luteolin 3′,4′-dimethyl ether, jaceosidin, 5,7,4′-trihydroxy-3,6-dimethoxyflavone, tricin, hispidulin, chrysoeriol, kaempferol 3-methyl ether, apigenin, axillarin, eupafolin, selagin and luteolin together with three flavones which were previously isolated for the first time from Artemisia frigida: 5,7,4′-trihydroxy-6, 3′,5′-trimethoxyflavone, 5,7,3′-trihydroxy-6,4′,5′-trimethoxyflavone and 5,7,3′,4′-tetrahydroxy-6,5′- dimethoxyflavone.     

Novel topologically knotted DNA from bacteriophage P4 capsids: studies with DNA topoisomerases.

DNA molecules isolated from bacteriophage P4 are mostly linear with cohesive ends capable of forming circular and concatemeric structures. In contrast, almost all DNA molecules isolated form P4 tailless capsids (heads) are monomeric DNA circles with their cohesive ends hydrogen-bonded. Different form simple DNA circles, such P4 head DNA circles contain topological knots. Gel electrophoretic and electronmicroscopic analyses of P4 head DNA indicate that the topological knots are highly complex and heterogeneous. Resolution of such complex knots has been studied with various DNA topoisomerases. The conversion of highly knotted P4 DNA to its simple circular form is demonstrated by type II DNA topoisomerases which catalyze the topological passing of two crossing double-stranded DNA segments [Liu, L. F., Liu, C. C. & Alberts, B. M. (1980) Cell, 19, 697-707]. The knotted P4 head DNA can be used in a sensitive assay for the detection of a type II DNA topoisomerase even in the presence of excess type I DNA topoisomerases.     

Iatrogenic hyponatraemia of the newborn due to maternal fluid overload: a prospective study.

Over five weeks 136 out of 246 deliveries were studied. Maternal plasma sodium concentrations were normal at admission. At delivery no significant difference was found between maternal and infant cord plasma sodium concentrations. Twenty-four of the 41 mothers who had received only oral fluids during labour had infants whose cord plasma sodium concentrations were normal. Of the 95 mothers who had been given intravenous fluids, however, only 14 infants with normal plasma sodium concentrations, 31 had a concentrations of 130 mmol (mEq)/1 or less and nine of these had a concentration of 125 mmol/1 or less. There was a highly significant inverse relation between cord plasma sodium concentration and rate of fluid administration, suggesting that hyponatraemia was due to intravenous treatment with predominantly sodium-free solutions. Endogenous antidiuretic activity probably increases during labour, and synthetic oxytocin in large doses has been shown to have an antidiuretic effect. The dose used in this study did not appear to have such an effect. Glucose solutions are often used as a vehicle for oxytocin; 83% of all fluid intake in this study was 5% or 10% glucose in water. Fluid balance in labour should be supervised closely, and oxytocin should be given in a more concentrated solution.     

Ly-m19: The Lyb-2 region of mouse chromosome 4 controls a new surface alloantigen

Spleen cells from an SJL mouse immunized with 70'/3 cells, an established pre-B cell line, were fused with cells of the nonsecretor myeloma line NS.1. One established hybridoma cell line (clone K10.6) continuously secreted antibody that recognized a new antigenic specificity tentatively named Ly-m19. This newly found antigen is detectable on both T and B cells. Cytotoxicity assays reveal that 75 percent of the spleen and lymph-node cells, 35 percent of bone-marrow cells, and 15 percent of thymus cells reacted with antibody of clone K10.6. Strains expressing the specificity Ly-m19.1 are characterized by negative reactions and include the strains AKR, CE/J, RF/J, GR/A, SJL, P/J, BDP/J, and LG/J. All other strains so far tested are Ly-m19.2. This strain distribution pattern distinguishes Ly-m19 from any known murine lymphocyte alloantigen, but it parallels the Lyb-2 ^c haplotype. Linkage test of a set of AKXL recombinant inbred strains revealed close linkage of Ly-m19 and Lyb-2 loci on mouse chromosome 4.Abbreviations used in this paper LPS lipopolysaccharide - B6 C57BL/6 - Con-A concanavalin A - MLC mixed-lymphocyte culture The prefix m (monoclonal) is used following a suggestion by Klein and co-workers (1979).