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31.
Noritsugu Yabe Yutaka Matsuya Isao Yamane Mitsuru Takada 《In vitro cellular & developmental biology. Plant》1986,22(7):363-368
Summary A newly developed, serum-free medium (NYSF-404) selects for antibody-producing hybridomas after fusion of antigen-sensitized
mouse spleen cells with myeloma cell lines P3-X63-Ag8-U1 (P3-U1), P3-X63-Ag8-6.5.3 (Ag8.653), or P3-NSI/1-Ag4-1 (NS-1). Without
the need for hypoxanthine-aminopterinthymidine (HAT) selection of hybrid cells, frequency of hybridoma formation in medium
NYSF-404 is higher (twice) than that in serum- and HAT-containing medium. Colonies developed upon limiting dilution in the
presence of the mortal parent myeloma cells in medium NYSF-404 and pure culture of antibody-secreting cells could be subsequently
established. The results suggest that fusions can be done in serum-free medium and that the clonal growth of hybridomas is
dependent on factors produced by parent myeloma cells under serum-free culture conditions. Such factors seem deficient in
serum- and HAT-containing medium or are masked by serum. 相似文献
32.
A relation between gene dosage and UDP-glucose:flavonoid 3-O-glucosyl-transferase (UFGT) activity was found in homozygous dominant and recessive parental lines and their F1 progeny for both of the genes An1 and An2. In both F2 crosses, progeny plants could be classified as belonging to groups showing either a low or a medium to high UFGT activity. Test crosses showed that heterozygous and homozygous dominant plants were present throughout the medium- to high-active group. The dosage relation in F2 plants is most probably confounded by the segregation of modifiers. Thermal inactivation experiments indicated that structurally different UFGT enzymes are formed in homozygous dominant lines as well as in lines homozygous recessive for either An1 or An2. Lines homozygous recessive for the gene An4 contain a UFGT with a half-life time at 55° C of less than 8 min, whereas UFGTs from lines homozygous dominant for An4 show a half-life time of 25 min or above, with one exception. This relation was confirmed in the F2 progeny; heterozygotes for An4 showed an intermediate half-life time. It is concluded that An4 might be the structural gene for the enzyme; An1 and An2 are both regulatory genes. UFGT activity in flowerbuds of An4/An4 plants seems to be lower than in an4/an4 plants. Anthers of flowers of an4/an4 lines, however, are virtually devoid of UFGT activity. 相似文献
33.
A combined single-turnover flash and 35Cl NMR technique has been used to monitor S-state dependence of Cl− binding to PS-II particles derived from mangrove (Avicennia marina). No detectable high-affinity binding was found to particles in the S0 and S1 states, but binding with an affinity comparable to that which activates O2 evolution was found in the S2 and S3 states. 相似文献
34.
K. D. Hahn F. Buck H. Rüterjans B. K. Chernov K. G. Skryabin M. P. Kirpichnikov 《European biophysics journal : EBJ》1985,12(2):87-95
The 17 base pair operator O
R
3 oligonucleotide, which is the preferential binding site for the Cro repressor of phage , was studied by two-dimensional NMR spectroscopy. A sequential assignment procedure based on two-dimensional Nuclear Overhauser Effect (NOESY) and scalar coupling correlated (COSY) NMR spectroscopy, together with the knowledge of the oligodesoxynucleotide sequence, made it possible to assign the non-exhangeable base protons and the H1 and the H2-H2 sugar protons of the O
R
3 operator DNA. The pattern of the observed NOE connectivities is consistent with a right-handed helical DNA structure. The base and sugar proton assignments provide the necessary information for further studies of the O
R
3 operator — Cro repressor interaction.Abbreviations COSY
correlated spectroscopy
- FID
free induction decay
- NOE
nuclear Overhauser effect
- NOESY
nuclear Overhauser effect spectroscopy
- RD
relaxation delay
- TSP
sodium 3-trimethylsilyl-(2,2,3,3-2H4)propionate
- EDTA
sodium ethylendiamine tetraacetate 相似文献
35.
V. G. Tumanyan Yu. A. Neyfack M. K. Pirtskhalava J. H. Männik 《Journal of biosciences》1985,8(3-4):593-602
On the basis of complete scanning through conformational space of dihedral angles, twelve structural genera were obtained.
Subsequent energy minimization within these genera yielded a limited set of duplexes with stacking: right-handed B-form (Wilkins
type), B2-form (Watson and Crick type) and left-handed Ll-form (Sasisekharan type) and the new L2-form. In the polymeric DNA
only right-handed double-helices are possible, the left-handed helices are forbidden due to poor 1–5 interchain contacts.
In contrast, for short fragments the left- and right-handed helicek have practically the same energies providing some physical
ground for side-by-side form, which biologically is possible as recombination form and may be as replication form. 相似文献
36.
Prof. L. Vollrath M. Karasek B. Kosaras J. Kunert-Radek A. Lewinski 《Cell and tissue research》1985,242(3):607-611
Summary Previous studies have shown that the synaptic ribbons (SR) and spherules (SS) of the mammalian pineal gland may respond differently under physiological and various experimental conditions. The aim of the present study was to gain insight into the mechanisms that may be responsible for the numerical changes of these organelles during a 24-h cycle. As the possibility exists that the structures are influenced by substances synthesized within the pinealocyte, rat pineal glands were cultured with and without added melatonin or serotonin, using an experimental protocol such that the addition of melatonin and serotonin mimicks the circadian changes of the respective substances within the pineal. The tissue was processed for electron microscopy and the numbers of SR and SS were counted in a unit area of pineal tissue. The results obtained indicate that melatonin added to the incubation medium increases the number of SR in the first half of the night; serotonin decreases SR numbers in the morning. SS numbers, by contrast, decrease following melatonin administration in the afternoon, and increase in the morning following serotonin administration. It thus appears that the numbers of SR and SS are influenced by melatonin and serotonin and that the two structures are regulated by differential, but nevertheless biochemically closely related mechanisms.Financial support of the Deutsche Forschungsgemeinschaft (Schwerpunktprogramm Neuroendokrinologie, Vo 135/8-4), the Polish Academy of Sciences (Research Program 10.4.04.6), and the Freunde der Universität Mainz e.V. is gratefully acknowledged.On leave from Department of Anatomy, University Medical School, Pécs, Hungary 相似文献
37.
Optimum growth conditions for the fermentation of non-concentrated whey permeate by Kluyveromyces fragilis NRRL 665 have been defined. Use of 3.75 g yeast extract l?1, a growth temperature of 38°C and a pH of 4.0 allowed a maximum productivity of 5.23 g ethanol l?1 h?1 in continuous culture with a yield 91% of theoretical. Complete batch fermentation of permeate with 100 g lactose l?1 was possible with a maximum specific growth rate of 0.276 h?1 without any change in ethanol yield. Fermentation of concentrated permeate resulted, however, in a general decrease of specific substrate consumption rate, demonstrated by the inability to completely convert an initial 90 or 150 g lactose l?1 in continuous culture, even at dilution rates as low as 0.05 and 0.08 h?1, respectively. The decrease could be related to substrate inhibition, to an increase in osmotic pressure caused by lactose and salts, and to ethanol inhibition of both alcohol and biomass yield. The decrease in specific productivity could be counterbalanced by use of high cell density cultures, obtained by cell recycle of K. fragilis. Fermentation of a non-concentrated permeáte at a dilution rate of 1 h?1 resulted in a productivity of 22 g l?1 h?1 at 22 g ethanol l?1. Cell recycle using flocculating Kluyveromyces lactis NCYC 571 was also tested. With this strain a productivity of 9.3 g l?1 h?1 at 45 g product l?1 was attained at a dilution rate of 0.2 h?1, with an initial lactose concentration of 95 g l?1. 相似文献
38.
Abstract Glycine added to the growth medium of Caulobacter crescentus was found to substitute Cterminal alanine in the peptide side chains of the murein of this species. Murein synthesized in vivo and in vitro in the presence of glycerine was poorly crosslinked as was new murein formed in the presence of the amino acid. The reduced cross-linkage seems to be due to the effect of glycine on the formation of trimeric muropeptides as revealed by high-performance liquid chromatography (HPLC) muropeptide analysis of murein formed in the presence and absence of the amino acid. 相似文献
39.
Detection of rapid induction kinetics with a new type of high-frequency modulated chlorophyll fluorometer 总被引:21,自引:0,他引:21
U. Schreiber 《Photosynthesis research》1986,9(1-2):261-272
A newly developed modulation fluorometer is described which operates with 1 sec light pulses from a light-emitting diode (LED) at 100 KHz. Special amplification circuits assure a highly selective recording of pulse fluorescence signals against a vast background of non-modulated light. The system tolerates ratios of up to 1:107 between measuring light and actinic light. Thus it is possible to measure the dark fluorescence yield and record the kinetics of light-induced changes. A high time resolution allows the recording of the rapid relaxation kinetic following a saturating single turnover flash. Examples of system performance are given. It is shown that following a flash the reoxidation kinetics of photosystem II acceptors are slowed down not only by the inhibitor DCMU, but by a number of other treatments as well. From a light intensity dependency of the induction kinetics the existence of two saturated intermediate levels (I1 and I2) is apparent, which indicates the removal of three distinct types of fluorescence quenching in the overall fluorescence rise from F0 to Fmax.Abbreviations QA and QB
consecutive electron acceptors of photosystem II
- PS II
photosystem II
- P 680
reaction center chlorophyll of photosystem II
- F0
minimum fluorescence yield following dark adaptation
- Fmax
maximum fluorescence yield
- DCMU
3-(3, 4-dichlorophenyl)-1, 1-dimethyl-urea
- DCCD
N,N-dicyclohexylcarbodiimide
- PQ
plastoquinone
- DAD
diaminodurene
Dedicated to Prof. L.N.M. Duysens on the occasion of his retirement. 相似文献
40.
Summary Mutations in seven different maternal-effect loci on the second chromosome of Drosophila melanogaster all cause alterations in the anterior-posterior pattern of the embryo. Mutations in torso (tor) and trunk (trk) delete the anterior- and posterior-most structures of the embryo. At the same time they shift cellular fates which are normally found in the subterminal regions of the embryo towards the poles. Mutations in vasa (vas), valois (vls), staufen (stau) and tudor (tud) cause two embryonic defects. For one they result in absence of polar plasm, polar granules and pole cells in all eggs produced by mutant females. Secondly, embryos developing inside such eggs show deletions of abdominal segments. In addition, embryos derived from staufen mothers lack anterior head structures, embryos derived from valois mothers frequently fail to cellularize properly. Mutations in exuperantia (exu) cause deletions of anterior head structures, similar to torso, trunk and staufen. However in exu, these head structures are replaced by an inverted posterior end which comprises posterior midgut, proctodeal region, and often malpighian tubules.The effects of all mutations can be traced back to the beginning stages of gastrulation, indicating that the alterations in cellular fates have probably taken place by that time. Analysis of embryos derived from double mutant mothers suggests that these three phenotypic groups of mutants interfere with three different, independent pathways. All three pathways seem to act additively on the system which specifies anterior-posterior cellular fates within the egg. 相似文献