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71.
Bruce M. Campbell 《Plant Ecology》1986,66(1):3-16
The vegetation of the mountains of the Fynbos Biome is classified and described, mostly on the basis of vegetation structure and higher taxa. Various gradients can be recognized. A gradient in soil conditions runs from coarse textured, nutrient-poor soils in non-grassy fynbos (Mountain Fynbos) through grassy fynbos and grassy non-fynbos (Eastern Fynbos and Grasslands & Grassy Shrubland) to finer textured and less nutrient-poor soils in the non-fynbos Karroid & Renoster Shrubland. Another gradient of significance can be likened to the tropical gradient running from the dry conditions of hot semi-deserts to savannas or grasslands to woodlands. At the dry extreme an open shrubland occurs (Karroid & Renoster Shrubland, Asteraceous Fynbos), at intermediate positions a herbland occurs (Restioid Fynbos) and at the wet extreme another type of shrubland occurs (Ericaceous Fynbos). This kind of moisture gradient occurs on individual mountains with the xeric end being at the base of the north slopes, and the mesic end being on the upper south aspects. Soil characteristics are closely linked to this gradient; the better developed soils being found on the south aspects. Another moisture gradient is apparent in the vegetation. This gradient runs from the mesic southern coastal mountains to the north west where summer droughts are extremely severe although total rainfall may be similar.Nomenclature follows that used in the Government Herbarium, Stellenbosch.I thank William Bond, Richard Cowling, John Rushworth, Eddy van der Maarel and Marinus Werger for critical comments and discussion. 相似文献
72.
Bruce H. Allen 《Brittonia》1988,40(2):180-187
Fontinalis welchiana, a new species in the concave-leaved group ofFontinalis restricted to Arkansas, Missouri, and Illinois, differs fromF. novaeangliae by its slender size, dimorphic leaves, erect and strongly concave branch leaves, and lightly papillose exostome with ventral lamellae that are strongly rounded at the corners.Fontinalis allenii is a synonym ofF. antipyretica var.oreganensis. 相似文献
73.
Dopamine Metabolism in Hypoxanthine-Guanine Phosphoribosyltransferase-Deficient Variants of PC12 Cells 总被引:2,自引:1,他引:1
Lesch-Nyhan syndrome results from a deficiency of hypoxanthine-guanine phosphoribosyltransferase (HPRT). It is manifest by behavioral abnormalities, including self-mutilation, and evidence of abnormal 3,4-dihydroxyphenylethylamine (dopamine) metabolism. To assess whether an HPRT deficiency in a dopaminergic cell can adversely affect dopamine metabolism in that cell, dopamine metabolism was examined in HPRT-deficient variants of PC12 pheochromocytoma cells and in cells that had regained HPRT activity by virtue of transformation with a recombinant retrovirus containing the human gene for HPRT. There was no correlation between HPRT activity and endogenous dopamine levels, dopamine uptake, dopamine release, or monoamine oxidase activity. Transformation with the HPRT retrovirus did not adversely affect dopamine metabolism. 相似文献
74.
Alfredo Munoz-Rivas Charles A. Specht Bruce J. Drummond Eunice Froeliger Charles P. Novotny Robert C. Ullrich 《Molecular & general genetics : MGG》1986,205(1):103-106
Summary Protoplasts of aSchizophyllum commune tryptophan auxotroph (trp1), deficient in indole-3-glycerol phosphate synthetase (IGPS), were transformed to trp+ with plasmid DNA containing the SchizophyllumTRP1 sequence. Efficiencies up to 30 transformants per microgram of plasmid DNA were obtained. Southern blots reveal that the
transforming DNA is integrated in chromosomal DNA. The trp+ phenotype of transformants is stable in meiosis and mitosis. Transformants possess IGPS activity comparable to wild-type
cells. 相似文献
75.
Production of bulblets of Muscari armeniacum through tissue culture is enhanced when 1 g/l activated charcoal is added to a modified Murashige and Skoog (MS) medium. Bulblet regeneration is direct from bulb scale explants with no intermediate callus growth. Bulblets can be transferred successfully to a greenhouse environment directly from aseptic culture. 相似文献
76.
77.
Free radical damage to cultured porcine aortic endothelial cells and lung fibroblasts: Modulation by culture conditions 总被引:5,自引:0,他引:5
Clark T. Bishop Zermeena Mirza James D. Crapo Bruce A. Freeman 《In vitro cellular & developmental biology. Plant》1985,21(4):229-236
Summary Culture conditions modulating cell damage from xanthine plus xanthine oxidase-derived partially reduced oxygen species were
studied. Porcine thoracic aorta endothelial cells and porcine lung fibroblasts were maintained in monolayer culture. Cells
were prelabeled with51Cr before xanthine plus xanthine oxidase exposure. Endothelial cells showed 30 to 100% more lysis than fibroblasts and thus
seemed more sensitive to this oxidant stress. The effect of cell culture age, as indicated by population doubling level (PDL),
was examined. Response of low PDL endothelial cells and fibroblasts subjected to oxidant stress was compared with the response
of PDL 15 cells. Both low PDL endothelial cells and fibroblasts responded differently to the lytic effect of xanthine oxidase-derived
free radicals than did higher PDL cells. Specific activities of the antioxidant enzymes catalase, managanese superoxide dismutase,
copper-zinc superoxide dismutase, glutathione peroxidase, and glucose-6-phosphate dehydrogenase were measured in both low
and high PDL fibroblasts and endothelial cells. Antioxidant enzyme specific activities could only partially explain the differences
in response to oxidant stress between fibroblasts and endothelial cells and between low and high PDL cells. Cell culture medium
composition modulated the rate of production, and relative proportions of xanthine plus xanthine oxidase-derived partially
reduced species of oxygen, i.e. superoxide, hydrogen peroxide, and hydroxyl radical. Serum content of medium was important
in modulating free radical generation; superoxide production rates decreased 32%, H2O2 became undetectable, and hydroxyl radical generation decreased 54% in the presence of 10% serum. The medium protein and iron
content also modulated free radical generation. The data suggest that cell culture media constituents, cell type, and cell
culture age greatly affect in vitro response of cells subjected to oxidant stress.
Research supported by American Lung Association Fellowship Training Grant and Research Training Grant, the R. J. Reynolds
Corporation, and National Institutes of Health Grants HL29784 and 1 HL 23805. 相似文献
78.
The NAD glycohydrolase (NADase) from Bungarus fasciatus snake venom was adsorbed on concanavalin A-Sepharose, and demonstrated to retain both hydrolase and transglycosidase activities in the bound form. The matrix-bound enzyme was stable to repeated washing with buffer and storage at 4°C. The bound enzyme exhibited the same Km value for hydrolysis of nicotinamide-1,N6-ethenoadenine dinucleotide as previously measured with the soluble, purified form of the enzyme. The bound NADase was used repeatedly for a preparative-scale synthesis of 3-acetylpyridine adenine dinucleotide. It was further demonstrated that the immobilized enzyme could be prepared directly from crude snake venom, thus avoiding the time required for purification. The application of the immobilized snake venom NADase for the preparation of pyridine nucleotide coenzyme analogs has many advantages over procedures used previously for analog synthesis. 相似文献
79.
The effects of Ca2+ and calmodulin on endogenously catalyzed ADP-ribosylation were investigated in adipocyte plasma membranes. Four specific proteins of 70, 65, 61 and 52 kDa were labeled with [32P]ADP-ribose and ADP-ribosylation of the proteins was highly dependent upon the conditions employed. ADP-ribosylation of the 70 kDa protein was observed only in membranes supplemented with Ca2+. Maximal incorporation of [32P] into the protein was achieved with free Ca2+ concentrations of 90 μM. Calcium-stimulated ADP-ribosylation of the 70 kDa protein was inhibited by calmodulin. Half-maximal inhibition was observed in membranes incubated with 1.2 μM calmodulin. The effect of calmodulin was characterized by an inhibition of the incorporation of [32P]ADP-ribose as opposed to a stimulation of its removal. ADP-ribosylation of the 61 kDa protein was not altered by added Ca2+ and/or calmodulin whereas ADP-ribosylation of the 65 kDa protein was partially (50%) inhibited by free Ca2+ concentrations between 10−6 – 10−5 M. These results provide evidence that the adipocyte plasma membrane contains ADP-ribosyltransferase activities and demonstrate that ADP-ribosylation of a 70 kDa protein is regulated by Ca2+ and calmodulin. 相似文献
80.
Flavonoids of the Hydrangeaceae Dumortier 总被引:3,自引:0,他引:3
Fourteen species representing nine genera of the Hydrangeaceae Dumortier were surveyed for their flavonoid pigments. All taxa exhibited profiles based upon common flavonols. Myricetin was seen in two genera: Jamesia and Decumaria. Jamesia was further distinguished by the absence of kaempferol or its glycosides. A complex array of 3-O-mono-, 3-O-di- and 3-O-triglycosides was observed, although not all species had all levels of glycosylation. Decumaria barbara was unique within the species studied in its possession of 3,7-di- and 3,7-triglycosides. The overall pattern of flavonol glycosides observed for the Hydrangeaceae closely resembles that found in herbaceous genera of Saxifragaceae. The comparatively low frequency of myricetin contrasts with its high occurrence in herbaceous genera. 相似文献