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951.
The dynamics of individual endogenous cytokinins within the growth cycle (subculture interval) of an auxin-dependent and cytokinin-independent cell suspension culture ofNicotiana tabacum L. (strain VBI-0) were determined using high performance liquid chromatography and radioimmunoassay. In cells grown at an optimum auxin concentration the transient maxima of N6-(2-isopentenyl)adenine and N6-(2-isopentenyl)-adenosine correlated with the onset of cell division. Cultivation of the cells in a partially auxin-deprived medium resulted in ca. tenfold increase of all endogenous cytokinins. A very distinct maximum of N6-(2-sopentenyl) adenine appeared at the beginning of subculture. This indicates that a lack of auxin induced an accumulation of cytokinins predominantly in the form of the free bases, which are physiologically more active than the corresponding ribosides.Abbreviations iP
N6-(2-isopentenyl)adenine
- [9R]iP
N6-(2-isopentenyl)adenosine
-
t-Z
trans-zeatin
-
t-[9R]Z
trans-zeatin riboside
- IAA
indole-3-acetic acid
- NAA
1-naphthaleneacetic acid
- 2,4-D
2,4-dichlorophenoxyacetic acid
- f.w.
fresh weight
- SBI
subculture interval
- C
complete medium
- PAD
partially auxin-deprived medium
- RP-HPLC
reverse phase high performance liquid chromatography
- RIA
radioimmunoassay
- PAL
L-phenylalanine ammonia lyase 相似文献
952.
M. T. Fernández-Espinar S. Vallés F. Piñaga J. A. Pérez-González D. Ramón 《Applied microbiology and biotechnology》1996,45(3):338-341
Using recombinant DNA techniques, an Aspergillus nidulans multicopy transformant for the gene xlnB coding for the minor X24 xylanase has been constructed. When grown on glucose as sole carbon source this transformant secretes 114 U of xylanase (mg
protein)-1. In this culture condition, X24 is the only xylanase secreted and the predominant protein in the culture filtrate. This strategy has been used to purify
the X24 enzyme to homogeneity. The purified xylanase showed a single band on sodium dodecyl sulphate/ polyacrylamide gel electrophoresis
with a molecular mass of 24 kDa and had an isoelectric point of approximately 3.5. The enzyme was a non-debranching endo-1,4-β-xylan
xylanohydrolase highly specific for xylans and showed optimal activity at pH 5.5 and 52°C. The X24 xylanase had a Michaelis constant, K
m, of 12.43 mg oat spelt xylan ml-1 and a V
max of 1639 μmol min-1 (mg protein)-1.
Received: 17 May 1995/Received last revision: 25 September 1995/Accepted: 29 September 1995 相似文献
953.
Both synthetic and natural ammonium-sorbing zeolite were used to control the NH+
4 level in Bacillus amyloliquefaciens cultures producing extracellular α-amylase. The addition of biochemically inert calcium aluminosilicates significantly increased
the yield of the enzyme. A simple mathematical model explaining the mechanism has been formulated and its parameters estimated.
Received: 1 August 1995/Received revision: 20 October 1995/Accepted: 24 October 1995 相似文献
954.
Forty-one isolates ofFusarium obtained from the main Argentinian corn production area were tested for their ability to produce moniliformin. One of 22 isolates ofF. moniliforme, 2/10 of F.proliferatum and 3/9 ofF. subglutinans, produced moniliformin in a range between 0,3 to 2,7 mg/g. These data represent the first report of the production of moniliformin byFusarium species from section Liseola in Argentina. 相似文献
955.
Pelouch Václav Kolář František Khuchua Zaza A. Elizarova Galina V. Milerová Marie Ošt'ádall Bohuslav Saks Valdur A. 《Molecular and cellular biochemistry》1996,163(1):67-76
The effect of chronic administration of -guanidinopropionic acid (GPA) on the protein profiling, energy metabolism and right ventricular (RV) function was studied in the rat heart during the weaning and adolescence period. GPA was given in tap water (1–1.5%) using pair drink controls. The feeding of animals with GPA solution for a six week period resulted in elevation of heart to body weight ratio due to body growth retardation. GPA accumulated in the myocardium up to 67.37 ± 5.3 moles.g dry weight and the tissue content of total creatine, phosphocreatine and ATP was significantly decreased to 15%, 9% and 65% of control values respectively. Total activity of creatine kinase (CK) was not changed, but the proportion of mitochondrial (Mi) CK isoenzyme was decreased; the percentage of MB isoenzyme of CK was significantly higher. GPA treatment resulted in an elevation of the content of cardiac collagenous proteins and decrease of non-collagenous proteins in the heart; in parallel, a decrease of the collagen I to collagen III ratio was detected. The function of the RV was assessed using an isolated perfused heart with RV performing pressure-volume work. As compared to pair-drink controls, RV function was significantly impaired the GPA group: at any given right atrial filling pressure, the RV systolic pressure and the rate of pressure development were decreased by almost a factor of two. Elevation of the RV diastolic pressure with increasing pulmonary artery diastolic pressure was also significantly steeper in the GPA group which also showed decrease of cardiac output, especially at high outflow resistance. It may be assumed that chronic administration of GPA deeply influenced metabolic parameters, protein profiles and contractile function of the developing heart. On the other hand, concentrations of glucose, total lipids and triglycerides in blood plasma were not affected. All these data confirm the concept that the CK system is of central importance both for heart function and for the regulation of normal growth of cardiac myocytes. 相似文献
956.
In the present study we investigated if administration of vitamin A could protect rat liver microsomes and mitochondria from in vitro peroxidation. Appreciable decrease of chemiluminescence and lipid peroxidation was measured in microsomal membranes from rats receiving vitamin A, with respect to control animals. In membranes derived from control animals, the fatty acid composition was profoundly modified when subjected to in vitro peroxidation mediated by ascorbate-Fe++, with a considerable decrease of 20:4 n6 and 22:6 n3 in mitochondria and 18:2 n6 and 20:4 n6 in microsomes. As a consequence the peroxidizability index, a parameter based on the maximal rate of oxidation of specific fatty acids was higher in supplemented animals than in control group when both kind of membranes were analyzed. These changes were less pronounced in membranes derived from rats receiving vitamin A. These results are in agreement with previous results that indicated that vitamin A may act as an antioxidant protecting membranes from deleterious effects.Abbreviations BHT
butylated hydroxytoluene
- BSA
bovine serum albumin
- CL
chemiluminescence
- PI
peroxidizability index
Member of Carrera del Investigador Científico, Consejo Nacional de Investigaciones Cientificas y Técnicas de la Republica Argentina 相似文献
957.
V. Alvarez E. Coto S. González-Roces C. López-Larrea F. Setién C. López-Larrea 《Immunogenetics》1996,44(6):446-452
N-formyl peptides (FMLP) and complement fragment C5a are neutrophil chemoattractants. In humans, a single-copy gene was identified
for the C5a receptor, and the receptor for FMLP (FPR1) is encoded by a single gene that shows 53% amino acid similarity to
the C5aR. Two other humanFPR1 homologues,FPR-like 1 (FPR2/FPRL1) andFPR-like 2 (FPRL2) have been cloned. The human C5aR, FPR1, FPRL1, and FPRL2 are physically linked. By direct sequencing or by sequencing plasmid
clones we studied theC5aR andFPR genes from four non-human primates (chimpanzee, gorilla, orangutan, and macaque). The sequences showed 95%–99% similarity
to the human homologues, with the major divergences observed in macaque. In these genes, the transmembrane and the cytoplasmic
domains are highly conserved, while the highest divergence corresponded to the extracellular loops involved in ligand binding.
Additionally, we constructed a physical map of these genes in non-human primates. In all species the four genes were physically
linked and we defined the relative orientation of the four genes in primates:C5aR>FPR1>FPR2 (FPRL1)>FPRL2.
The nucleotide sequence data reported in this paper have been submitted to the EMBL/GenBank nucleotide sequence databases
and have assigned the accession numbers X97730 (PTC5aR), X97731 (MMC5aR), X97732 (PPC5aR), X97730 (GGC5aR), X97734 (MMFPR1), X97735 (PPFPR1), X97736 (GGFPR1), X97737 (MMFPRL1), X97738 (GGFPRL1), X97739 (PTFPRL1), X97740 (MMFPRL2), X97741 (PPFPRL2), X97742 (GGFPRL2), X97743 (PTFPRL2), X97744 (PPFPRL1), and X97745 (PTFPR1) 相似文献
958.
Summary Fe (III) and Cu (II) each at 50 M in four commercial strains of Saccharomyces cerevisiae induced an increase of NAD(P)+ reduction in one strain (Turkish), but two others (Chilean and Brazilian), the presence of Fe(III) and/or Cu(II) diminished NAD(P)+ reduction presumably due to free radicais formation inside these living cells. Suprisingly, in the American strain, Fe(III) induced a decrease and Cu (II) an increase of NAD(P)+ reduction. 相似文献
959.
In order to estimate the potential utilization of N2-fixing (heterocystous) cyanobacteria as natural biofertilizers in the Valencian rice fields (Spain), the distribution and seasonal variation of these microorganisms in water and sediment samples were evaluated, and the relationships among cyanobacterial abundance and physical and chemical characteristics of soil and water were investigated. N2-fixing cyanobacteria were present in all the samples analyzed (25 sampling points sampled three times per year during two years). The relative cyanobacterial abundance in soil and water followed contrasting patterns, maximum presence in soil coincided with minimum abundance in water. Correlation analysis showed that cyanobacterial abundance in the two phases (water and sediment) was influenced more by water than by soil properties. Salinity, mineralization variables, and soluble reactive phosphate (SRP) correlated positively with heterocystous cyanobacteria presence. Furthermore, dissolved inorganic nitrogen (DIN) and the ratio DIN: SRP correlated negatively with cyanobacterial abundance. However DIN: SRP ratio better described the cyanobacterial distribution, with a threshold effect: below the Redfield ratio value (7.2 in mass units) cyanobacterial abundance was clearly higher.
Correspondence to: A. Quesada. 相似文献
960.