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21.
Spectrophotometric assay for ornithine decarboxylase 总被引:11,自引:0,他引:11
That T. Ngo Kurt L. Brillhart Rowland H. Davis Raphael C. Wong Jack H. Bovaird Joseph J. Digangi Janet L. Ristow J. Lawrence Marsh Andrew P. H. Phan Howard M. Lenhoff 《Analytical biochemistry》1987,160(2):290-293
A rapid and sensitive spectrophotometric assay for ornithine decarboxylase is described. It is based on the observation that the product of ornithine decarboxylase, putrescine, reacts with 2,4,6-trinitrobenzenesulfonic acid to give a colored product soluble in 1-pentanol whereas ornithine does not. The amount of putrescine produced by the enzyme was determined by measuring the absorbance of the 1-pentanol extract of the reaction mixture at 420 nm, and by comparing the results to those obtained by the trapping of 14CO2 and by HPLC assays. The three assays were found to be equivalent in sensitivity, with the spectrophotometric assay having the advantages of being relatively rapid, requiring only common laboratory equipment, and not requiring the use of radioactive isotopes. 相似文献
22.
A study was conducted to investigate endocrine and testicular changes in the male chicken associated with the ingestion of 10 or 20 ppm aflatoxin at 3 different stages of development. Weekly body weight gain, absolute and relative combined testes weights, and plasma testosterone concentrations were reduced in aflatoxin-fed males as compared to controls, with the greatest differences seen at 12 wk of age. The effect of dietary aflatoxin on levels of plasma luteinizing hormone (LH) was dependent on age at exposure. Concentrations of plasma LH in 6-wk-old control males were significantly higher than in aflatoxin-fed birds, whereas no treatment differences were observed in older males. Additionally, few changes were observed in static levels of monoamines in any of the brain regions assayed, regardless of age at exposure. The delay in peak levels of LH, as well as the suppression of plasma testosterone and testicular weight, indicate a possible delay in the onset of sexual maturation associated with aflatoxicosis in this species. 相似文献
23.
Rose C. Wade Janet V. Powers Cyril Ponnamperuma 《Origins of life and evolution of the biosphere》1989,19(2):199-220
This bibliography is the seventeenth annual supplement to the comprehensive bibliography on the same subject which was published in Space Life Sci. 2(1970), 225-295; 3(1972), 293-304; 4(1973), 309-329 and in Origins of Life 5(1974), 505-527; 6(1975), 285-300; 7(1976), 75-85; 8(1977), 59-66; 9(1978), 67-74; 10(1980), 69-87; 10(1980), 379-404; 11(1981), 273-288; 12(1982), 93-118; 13(1983), 61-80; 15(1984), 55-69; 17(1987), 171-184; 17(1987), 185-206. 相似文献
24.
Transformation by Complementation of an Adenine Auxotroph of the Lignin-Degrading Basidiomycete Phanerochaete chrysosporium 总被引:4,自引:1,他引:3
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Margaret Alic Janet R. Kornegay David Pribnow Michael H. Gold 《Applied microbiology》1989,55(2):406-411
Swollen basidiospores of an adenine auxotroph of Phanerochaete chrysosporium were protoplasted with Novozyme 234 and transformed to prototrophy by using a plasmid containing the gene for an adenine biosynthetic enzyme from Schizophyllum commune. Transformation frequencies of 100 transformants per μg of DNA were obtained. Southern blot analysis of DNA extracted from transformants demonstrated that plasmid DNA was integrated into the chromosomal DNA in multiple tandem copies. Analysis of conidia and basidiospores from transformants demonstrated that the transforming character was mitotically and meiotically stable on both selective and nonselective media. Genetic crosses between double mutants transformed for adenine prototrophy and other auxotrophic strains yielded Ade− progeny, which indicated that integration occurred at a site(s) other than the resident adenine biosynthetic gene. 相似文献
25.
Glass-beads (diam. = 250 μm) were buried 10 cm deep in the sediment of a stream. After an exposure of eight weeks, bacterial
densities on the beads varied between 2.7 × 105 and 2.4 × 107/cm2, and the length of the fungal mycelium between 0.2 and 5.3 mm/cm2. Bacterial densities did not show any correlation with the DOC content of the water, but were positively correlated with
respiration on the beads. Fungal mycelium was negatively correlated with water temperature. Acid hydrolysis of stream-exposed
beads released sugars and amino acids, whose combined carbon content exceeded that of the microbial cells by a factor of at
least 4. Gut extracts of Gammarus tigrinus and Tipula caloptera released amino acids and sugars from stream-exposed beads. 相似文献
26.
Hair morphology was exammed on developing seedlings and mature plants of ten species from five of seven series inPhysalis. The taxonomic importance of hair development and the distribution of hair types then was evaluated with respect to other comparative data. Two classes of hair types were observed, as found in earlier investigations ofSolanum andRhododendron. The first hair class comprises a sequence from unbranched hairs to dendroid-stelliform hairs. Hairs of this class show considerable variability among taxa in size, presence or absence of glandular tips, and presence and degree of branching, and so were useful in making taxonomic comparisons. The second hair class consists of short hairs, each tipped with a multicellular gland. This second hair class was not useful taxonomically because of its lack of variability in morphology and its often rare occurrence on a plant. The taxa studied exhibit distinctive trichome features which serve to distinguish series and, in some cases together with other data, provided new insight into previously enigmatic species relationships. 相似文献
27.
Control of myogenesis in the mouse myogenic C2 cell line by medium composition and by insulin: Characterization of permissive and inducible C2 myoblasts 总被引:14,自引:0,他引:14
Christian Pinset Didier Montarras Janet Chenevert Adrian Minty Paul Barton Christine Laurent Francois Gros 《Differentiation; research in biological diversity》1988,38(1):28-34
Using subcloning and manipulations of culture conditions we have isolated from the mouse myogenic cell line C2 a variant cell line that we named inducible. Unlike the progenitor cells that are referred to as permissive, inducible myoblasts differentiate poorly in Dulbecco modified Eagle medium plus fetal calf serum (FCS) and require the presence of insulin at a high concentration (1.6 10(-6) M) or insulin-like growth factor I (IGFI) at a lower concentration (2.5 10(-8) M) to differentiate. Permissive and inducible myoblasts fail to differentiate when grown in MCDB202 medium plus 20% FCS, even after a prolonged arrest in G1 phase. This shows that an arrest in G1 is in itself insufficient to trigger terminal differentiation. Both cell types also exhibit distinct patterns of accumulation of muscle mRNAs corresponding to sarcomeric actins and myosin light chain MLC1A. The possibility that these two cell lines might represent two different stages of the progression of myoblasts toward terminal differentiation is discussed. 相似文献
28.
Geraldine E. Oliva George W. Rutherford Moses Grossman Janet Shalwitz Abigail English Frances Taylor David Werdegar 《The Western journal of medicine》1988,148(5):586-589
Although adolescents account for only 0.4% of reported cases of the acquired immunodeficiency syndrome (AIDS) in the United States, they are sexually active and, therefore, at risk of acquiring human immunodeficiency virus (HIV) infection. To address issues of HIV control in adolescents, we developed guidelines that emphasize education and medical care and deemphasize antibody testing. For adolescents known to be infected with HIV, we recommend no restrictions on access to educational or treatment programs except when their health providers recommend such restrictions to protect them from exposure to opportunistic infections. For adolescents of unknown antibody status with a possible previous exposure to HIV, we recommend that as long as the incidence of HIV infection and clinical AIDS remains low, there should be no restrictions on residential placements and no routine antibody testing. 相似文献
29.
Judith R. Turnlund Leslie Wada Janet C. King William R. Keyes Lorra L. Acord 《Biological trace element research》1988,17(1):31-41
Copper absorption was measured at two levels of dietary zinc in six healthy young men who were confined to a metabolic unit
for a 75 d study of zinc utilization. A diet of conventional foods was fed, providing either 16.5 or 5.5 mg zinc and 1.3 mg
copper daily. Copper absorption was determined by feeding65Cu, a stable isotope of copper, once during the 16.5 mg Zn diet and near the beginning and end of the 5.5 mg Zn diet. Apparent
copper absorption averaged 48.1% when the 16.5 mg Zn diet was fed. This was significantly higher than the averages of 37.2
and 38.5% when the 5.5 mg Zn diet was fed. Absorption also differed significantly among subjects. Fecal copper did not differ
between diets or among subjects. All subjects were in positive copper balance at both levels of dietary zinc. These results
suggest that a dietary zinc intake slightly above the Recommended Dietary Allowance of 15 mg/d does not increase fecal copper
loss and does not interfere with copper absorption. 相似文献
30.
Age structure of nematode populations around maize growing in sandy soils in Iowa was studied at soil depths of 0-15and 15-30 cm for 2 years. Numbers of Longidorus breviannulatus were generally greater at 0-15 cm than at 15-30 cm deep until mid to late season. The decline in numbers of females as the season progressed indicates that fecundity slowed and is evidence of only one generation per year. Peak populations of Pratylenchus scribneri and Xiphinema americanum occurred in late August or early September. Adults of Hoplolaimus galeatus were few in the roots but common in the soil, indicating that fertilization occurred mostly in the soil. Numbers of P. scribneri were generally greater at the lower depth, especially late in the season. Community diversity (H'') was less when nematode biomass was used instead of numbers. Numbers of H. galeatus did not decline over the winter. Numbers of L. breviannulatus, P. scribneri, and X. americanum declined significantly over the winter, but not between spring cultivation and planting. 相似文献