广西北部罗汉果根结线虫病研究

罗汉果根结线虫是罗汉果的一个重要病害。在室内盆栽接种条件下,该线虫年发生6代。本文叙述了线虫的生物学及其寄主植物。防治试验结果表明。穴施灭克磷等是有效的。土壤翻晒也能消灭大部分土中线虫,病薯用热处理也有很好的效果。     

中药灵香草及其混淆品种的比较鉴别

本文比较了中药灵香草Lysimachia foenum-graecum Hance及其混淆品种垂花香草Lysimaehia nutantiflora Chen et C.M.Hu的植物形态、药材性状以及茎、叶组织显微特征。指出垂花香草无灵香草特有的芳香。也无药用记载。应仔细区别,不宜混用。     

水翁花蕾和水翁叶精油的化学成分研究

水翁的花营和鲜叶经水蒸汽蒸馏得到一种淡黄色的精油,前者出油率为0.18％。后者为0.08％。我们应用毛细管气相色谱,气相色谱/质谱联用,红外光谱和紫外光谱等方法,对两种精油进行化学分成分析,分别鉴定出35个和27个已知化学成分。两者相同的化学成分有:β-罗勒烯(Z)、β-罗勒烯(E)、α-蒎烯、β-蒎烯、月桂烯、小茴香烯、香叶醇、顺式-丁香烯、橙花叔醇等23个化学成分,分别占花营精油全油的90％和叶精油95％以上。     

Gene deletion, a mechanism of induced mutation by arabinosyl nucleosides

9-β- -Arabinofuranosyl-2-fluoroadenine (F-ara-A) and 9-β- -arabinofuranosyladenine (ara-A) are purine nucleoside analogues which are incorporated into nucleic acids. This study demonstrates the mutagenic properties of F-ara-A and ara-A and provides evidence for mechanisms by which the arabinosyl nucleosides induce mutation. At the drug dosages that evoked exponential cell killing, F-ara-A and ara-A caused a significant increase in the number of 6-thioguanine-resistant mutants in Chinese hamster ovary cells. Southern analyses showed that 15 of 16 drug-induced mutants had lost all or part of the HPRT gene, whereas no loss of the gene was found in 4 spontaneous mutants. We conclude that both F-ara-A and ara-A induced mutation predominantly by causing deletion of genetic method. The remarkable frequency of gene deletion among these drug-induced mutations is discussed with respect to possible mechanisms of action of arabinosyl nucleosides in mutational studies.     

Maintenance of low cl concentrations in mesophyll cells of leaf blades of barley seedlings exposed to salt stress

The concentrations of vacuolar Na⁺ and Cl⁻ in the epidermal and mesophyll cells of the leaf blade and sheath of Hordeum vulgare seedlings (cv California Mariout and Clipper) were measured by means of quantitative electron probe x-ray microanalysis. A preferential accumulation of Cl⁻ in vacuoles of epidermal cells in both blade and sheath and a low level in mesophyll cells of the blade were evident in plants grown in full strength Johnson solution. The concentration of Cl⁻ in the mesophyll cells of the blade remained at a low level after exposure to 50 or 100 millimolar NaCl for 1 day or to 50 millimolar for 4 days, while at the same time the concentration of Cl⁻ in the epidermis and mesophyll of the sheath showed a dramatic increase. Clipper generally contained more Cl⁻ in the mesophyll cells of the blade than California Mariout. A greater accumulation of Na⁺ in the mesophyll of the sheath relative to that of the blade was only apparent after treatment with 100 millimolar NaCl for 1 day or 50 millimolar for 4 days. These results confirm the suggestion that sheath tissue is capable of accumulating excess Cl⁻ (and to a lesser extent Na⁺) and suggest that the site of regulation of Cl⁻ concentration in the barley leaf is located in the mesophyll cells of the blade.     

Lysophosphatidate acyltransferase activities in the microsomes from palm endosperm, maize scutellum, and rapeseed cotyledon of maturing seeds

Lysophosphatidate (LPA) acyltransferase (EC 2.3.1.51) in the microsomes from palm endosperm (Syagrus cocoides Martius), maize scutellum (Zea mays L.), and rapeseed cotyledon (Brassica napus L.) of maturing seeds were studied for their specificities toward the acyl moiety of the substrates lysophosphatidate and acyl coenzyme A (CoA). The LPA acceptor greatly influenced the acyl CoA specificity of the enzyme and vice versa. With 1-oleoyl-lysophosphatidate (LPA-18:1), the palm enzyme was equally active on oleoyl CoA and lauroyl CoA, whereas the maize and rapeseed enzymes were more active on oleoyl CoA than on lauroyl CoA. With 1-lauroyl-lysophosphatidate (LPA-12), which generated less activity than LPA-18:1, the palm enzyme was three times more active on lauroyl CoA than on oleoyl CoA. LPA-12 was an inactive substrate for the maize and rapeseed enzymes. The selectivity of the enzymes was also studied using a mixture of LPA-18:1 and LPA-12, as well as lauroyl CoA and oleoyl CoA. Under this selectivity condition and compared to the specificity condition, the enzymes from all the three seeds exerted stronger preference for oleoyl moiety in either the LPA or acyl CoA, and again, only the palm enzyme could act on LPA-12. Similar studies, although in lesser detail, showed that the enzymes from soybean and castor bean were similar to the maize and rapeseed enzymes in having little activity on substrates containing lauroyl moiety. The results demonstrate the importance of the acyl group in the sn-1 position of LPA in determining the acyl preference in the sn-2 position in phosphatidate synthesis. The palm enzyme appears to be the only one capable of synthesizing phosphatidates containing high amounts of lauric moieties.     

Localization and Pattern of Graviresponse across the Pulvinus of Barley Hordeum vulgare

Pulvini of excised stem segments from barley (Hordeum vulgare cv `Larker') were pretreated with 1 millimolar coumarin before gravistimulation to reduce longitudinal cell expansion and exaggerate radial cell enlargement. The cellular localization and pattern of graviresponse across individual pulvini were then evaluated by cutting the organ in cross-section, photographing the cross-section, and then measuring pulvinus thickness and the radial width of cortical and epidermal cells in enlargements of the photomicrographs. With respect to orientation during gravistimulation, we designated the uppermost point of the cross-section 0° and the lowermost point 180°. A gravity-induced increase in pulvinus thickness was observable within 40° of the vertical in coumarin-treated pulvini. In upper halves of coumarin-treated gravistimulated pulvini, cells in the inner cortex and inner epidermis had increased radial widths, relative to untreated gravistimulated pulvini. In lower halves of coumarin-treated pulvini, cells in the central and outer cortex and in the outer epidermis showed the greatest increase in radial width. Cells comprising the vascular bundles also increased in radial width, with this pattern following that of the central cortex. These results indicate (a) that all cell types are capable of showing a graviresponse, (b) that the graviresponse occurs in both the top and the bottom of the responding organ, and (c) that the magnitude of the response increases approximately linearly from the uppermost point to the lowermost. These results are also consistent with models of gravitropism that link the pattern and magnitude of the graviresponse to graviperception via statolith sedimentation.     

Thrombolysis using liposomal-encapsulated streptokinase: an in vitro study

The clot-lysing ability of streptokinase (SK) was examined using membrane-bound thrombi. Encapsulation of SK in large unilamellar phospholipid vesicles (liposomes) resulted in entrapping approximately 30% of its original activity. Measurements of streptokinase activity for liposomal-encapsulated streptokinase (LESK) indicated little loss of activity or leakage in Tris-buffered saline over a 24-hr period at temperatures of 4 and 23 degrees C. However, incubation of free SK and LESK in platelet-poor plasma (PPP) at 37 degrees C resulted in a decrease of SK activity. The retention of SK activity in LESK was considerably higher than that of unentrapped SK. Clot-dissolving time (CDT) was measured by monitoring the pressure drop during slow filtration in plasma through membrane-bound thrombi. The results indicated that both LESK and free SK were able to activate the fibrinolytic system. Without prior incubation in PPP at 37 degrees C, the CDT of a SK and PPP mixture (SK/PPP) was 10.7 +/- 1.9 min (n = 12), while that of a LESK and PPP mixture (LESK/PPP) was 12.4 +/- 1.7 min (n = 12). The CDT-detected clot-lysing abilities of both SK and LESK were diminished by incubation in PPP, but to different extents. After 15- and 30-min incubations, the CDT of SK/PPP increased significantly to 15.5 +/- 1.5 and 24.1 +/- 2.4 min (n = 5, P less than 0.05), respectively. In contrast, the CDT of LESK/PPP increased to 13.3 +/- 0.8 min (n = 5) after 15 min of incubation and to 16.0 +/- 1.1 min (n = 5, P less than 0.05) after a 30-min incubation. These results suggest that entrapment of SK in liposomes preserves the thrombolytic potential of the plasminogen activator by limiting its exposure to the components of the plasma.     

Two structural genes on different chromosomes are required for encoding the major subunit of human red cell glucose-6-phosphate dehydrogenase

Structural analysis revealed the existence of two types of subunits in human red cell glucose-6-phosphate dehydrogenase. The two subunits have the same COOH region consisting of 479 amino acid residues, but their NH2-terminal regions are different in size and sequence. The minor subunit can be fully encoded by the X-linked G6PD cDNA, but the NH2-terminal region of the major subunit cannot. The cDNA and the gene for the NH2-terminal region of the major subunit were cloned and characterized. Southern blot hybridization indicated that the gene for the NH2-terminal region is on chromosome 6, not on the X chromosome. Northern blot hybridization demonstrated an existence of two separate mRNA components, one for the COOH-terminal region and the other for the NH2-terminal region. Two separate structural genes, the X-linked and chromosome 6-linked genes, must be coresponsible for encoding the single chain subunit. Either cross-translation of two mRNAs, or transpeptidation, or some other mechanism must be involved in the synthesis of human red cell G6PD.