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11.
One hundred and thirty Atlantic sharpnose shark Rhizoprionodon terraenovae livers were collected from April 1999 to October 2001 from inshore waters of the Mississippi Sound to investigate seasonal and inter‐annual variation in their energetic condition. A decline in the hepato‐somatic index ( I H ) was observed from 1999 to 2001. In addition, I H , liver specific energy content and total energy content were lowest during the summer and highest during the spring and autumn, while liver water content was highest during the summer and lowest during the spring and autumn. 相似文献
12.
13.
Protoplasts isolated from beetroot tissue took up glucose preferentially whereas sucrose was transported more slowly. The 14C-label from [14C]glucose and [14C]sucrose taken up by the cells could be detected rapidly in phosphate esters and, after feeding of [14C]glucose was found also in sucrose. The temperature-dependent uptake process (activation energy EA about 50 kJ · mol–1) seems to be carrier mediated as indicated by its substrate saturation and, for glucose, by competition experiments which revealed positions C1, C5 and C6 of the D-glucose molecule as important for effective uptake. The apparent Km(20° C) for glucose (3-O-methylglucose) was about 1 mM whereas for sucrose a significantly lower apparent affinity was determined (Km about 10 mM). When higher concentrations of glucose (5 mM) or sucrose (20 mM) were administered, the uptake process followed first-order kinetics. Carrier-mediated transport was inhibited by N,N-dicyclohexylcarbodiimide, Na-orthovanadate, p–chloromercuribenzenesulfonic acid, and by uncouplers and ionophores. The uptake system exhibited a distinct pH optimum at pH 5.0. The results indicate that generation of a proton gradient is a prerequisite for sugar uptake across the plasma membrane. Protoplasts from the bundle regions in the hypocotyl take up glucose at higher rates than those derived from bundle-free regions. The results favour the idea that apoplastic transport of assimilates en route of unloading might be restricted to distinct areas within the storage organ (i.e. the bundle region) whereas distribution in the storage parenchyma is symplastic.Abbreviations CCCP
Carbonylcyanide m–chlorophenylhydrazone
- DCCD
N,N-dicyclohexylcarbodiimide
- DOG
deoxyglucose
- Mes
2-(N-morpholino)ethanesulfonic acid
- 3-OMG
3-O-methylglucose
- PCMBS
p–chloromercuribenzenesulfonic acid
- SDS
Sodium dodecyl sulfate
- Tris
2-amino-2-(hydroxymethyl)-1,3-propanediol 相似文献
14.
Studies were conducted to compare N mineralization rates in salt-amended nonsaline soils to naturally-occurring saline soils.
NaCl, CaCl2, and Na2SO4 were added to nonsaline soils at rates that produced electrical conductivities of the saturation extracts (ECe) of 5, 10, 15, and 20 dS m−1. Saline soils with similar properties were leached to the same ECc levels. N mineralization in the Chino soil was inhibited by salt addition, particularly with sodium and calcium chlorides.
In the Domino soil there was some inhibition of N mineralization with the chloride salts, but enhancement with Na2SO4 was observed. Nitrification in both soils was more sensitive to salt addition than ammonification.
N mineralization occurred more slowly in both leached saline soils compared to the salt-amended soils. Leached saline soils
often accumulated greater amounts of inorganic N compared to their native saline counterparts, particularly with the 5 dS
m−1 Chino soil (native, 44 dS m−1) and with the 5, 10, 15 and 20 dS m−1 Domino soils (native, 32 dS m−1). Kinetic parameters were estimated by the linear least squares (LLS) and the nonlinear least squares (NLLS) methods. Generally,
the LLS transformation estimated greater values of potentially mineralizable N (No) and lower rate constants (k). With the NLLS equation, No values for the leached saline soils were usually lower, and k values usually higher than in the salt-amended soils. The nonsaline
controls generally had the highest No and lowest k estimates. Average LLS rate constants for the salt-amended and leached saline soils were 0.055 and 0.083 for
the Chino, and 0.104 and 0.137 week−1, respectively, for the Domino soils. With the NLLS equation, average k values for the salt-amended and leached saline soils
were 0.087 and 0.089 for the Chino, and 0.181 and 0.387 week−1, respectively, for the Domino soils. These results suggest that N mineralization rates obtained in salt-amended nonsaline
soils may not be representative of those in naturally-occurring saline soils. 相似文献
15.
Katsuya Koike Masato Mori Yukishige Ito Yoshiaki Nakahara Tomoya Ogawa 《Glycoconjugate journal》1987,4(2):109-116
The first total synthesis of glycosphingolipids isolated from wheat flour has been achieved in a regio- and stereo-controlled manner.Abbreviations THF
tetrahydrofuran
- DMF
dimethylformamide
Part 53 in the series Synthetic Studies on Cell Surface Glycans 相似文献
16.
Effect of maltose on the response of potato anthers in culture 总被引:1,自引:0,他引:1
Anthers of the Solanum tuberosum genotype H3703 were cultured on medium containing equimolar concentrations of sucrose or maltose. It was found that significantly more pollen embryos became plants after culture on maltose and hence the yield of plants per 100 anthers cultured increased significantly. Mechanisms by which carbohydrate source may influence response to anther culture are discussed. 相似文献
17.
Arthur H. L. From Dwight S. Fullerton Khalil Ahmed 《Molecular and cellular biochemistry》1990,94(2):157-165
The structure-activity relationships of the genin moieties of digitalis glycosides are commonly elucidated by determining the inhibitory potency of a variety of genins toward the plasma membrane Na+, K+-ATPase; qualitatively these relationships appear to be fairly independent of the specific Na+, K+-ATPase preparation utilized for the analysis. To determine whether this is the case with regard to the sugar moieties of glycosides, the inhibitory effects of 12 monoglycosides of digitoxigenin toward four Na+, K+-ATPase preparations of different origin were measured. It was found that while recognition of the major structural determinants of sugar activity appeared to be independent of enzyme source, recognition of the minor structural determinants of activity showed some source dependence. It was also observed that the intrinsic sensitivity to sugar potentiation may be source dependent and unrelated to intrinsic sensitivity to inhibition by digitoxigenin. These observations are compatible with a model of the Na+, K+-ATPase sugar binding site(s) in which intrinsic sensitivity to sugar attachment as well as recognition characteristics (for sugar structural features) both determine the extent to which a sugar moiety may contribute to the activity of monoglycosides. Further, in these studies one of the Na+, K+-ATPase preparations employed was obtained from rat brain, a tissue known to contain a mixture of ouabain sensitive and insensitive isoforms. We have observed that the rigorous purification techniques employed appear to have selectively removed from or denatured the less ouabain sensitive al isoform found in this enzyme preparation. 相似文献
18.
Alan J. Slusarenko 《Plant Molecular Biology Reporter》1990,8(4):249-252
A procedure which avoids the use of phenol-chloroform and RNAase for the isolation of total DNA fromA. tumefaciens is described. Specific precipitation of protein by 2.5 M ammonium acetate is employed and much of the RNA is removed by an isopropanol
precipition step. The procedure yields easily restrictable, good quality DNA and is probably applicable to other Gramnegative
bacteria. 相似文献
19.
Respiration and soluble sugar metabolism in sugar pine embryos 总被引:1,自引:0,他引:1
Embroys excised from dormant seeds of sugar pine ( Pinus lambertiana Dougl.) incubated at 25°C (non-dormancy-breaking) or stratified at 5°C (dormancy-breaking) were analyzed to determine temperature effects on the relative activities of respiration and fermentative metabolism, the levels of soluble sugers and the activities of the hydrolytic enzymes, invertase and sucrose synthase, as related to the release of dormancy and germinatio. At 25°C, despite a sharp drop in embryo oxygen uptake after 48 h, a simultaneous decline in acetaldehyde and ethanol concentrations indicated that there was not a shift to fermentative metabolism. The concentrations of soluble sugars showed no treatment effects. Embryo invertase (EC 3.2.1.26) activity changed only slightly at either temperature, while stratification was accompanied by a 4-fold increase in sucrose synthase (EC 2.4.1.13) activity (cleavage direction). Upon transfer of stratified seeds to 25°C, embryo sucrose synthase activity rapidly increased almost 10-fold, with the increase beginning prior to germination, while mvertase activity increased 20-fold, concomitant with germination. 相似文献
20.
Victor Chude 《Plant and Soil》1988,112(2):293-295
The profile distribution of total and extractable B was determined in 16 Nigerian cacao-growing soil profiles formed from
different parent materials. Total B for all soils ranged from 8 to 54μgg−1 with a mean of 24μgg−1. The soils formed from sandstones in the rainforest zone contained higher amounts of total B than soils derived from basement
complex. Boron extractable in hot water, in 0.1% CaCl2, and in 1N NH4OAc varied from 0.13 to 1.38, 0.44 to 1.20 0.03 to 0.56μgg−1 respectively. The corresponding means were 0.66, 0.75 and 0.27μgg−1 B. Soils on metamorphic rocks gave the highest values. All extractable B values were related to organic matter while only
CaCl2-extractable B correlated with total B. Generally total and extractable B values were higher in the top soils than in the
subsoils. 相似文献