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91.
Donald J. Cummings Léon Belcour Claude Grandchamp 《Molecular & general genetics : MGG》1979,171(3):239-250
Summary Mitochondrial (Mt) DNA from mitochondrial mutants of race s Podospora anserina and from senescent cultures of races s and A was examined. In mutants, we observed that fewer full length circles (31 ) were present; instead, smaller circles characteristic for each mutant sudied were found. Eco Rl digestion of these mutant MtDNAs indicated that in certain mutants, although specific fragments were absent, the total molecular weight of the fragments was not much different than wild-type.The properties of senescent MtDNA was strikingly different from either wild-type or mutant Mt DNA. First, a multimeric set of circular DNA was observed for both race s and A, with a monomeric repeat size of 0.89 . These circles ranged in size from 0.89 to greater than 20 ; only one molecule out of some 200 molecules was thought to be of full length (31 ). Density gradient analysis showed that there were two density species: a majority were at the same density as wild-type (1.694 g/cm3) and a second at 1.699 g/cm3. Most of the circular molecules from MtDNA isolated by either total DNA extraction or by extraction of DNA from isolated mitochondria were contained in the heavy DNA fraction. Eco R1 enzymatic digestion indicated that the light DNA had several fragments (amounting to about 23×106 daltons) missing, compared with young, wild-type MtDNA. Heavy senescent MtDNA was not cleaved by Eco R1. Analysis with Hae III restriction endonuclease showed also that light senescent MtDNA was missing certain fragments. Heavy MtDNA of average size 20×106 daltons, yielded only one fragment, 2,500 bp long, by digestion with Hae III restriction endonuclease. Digestion of heavy DNA with Alu I enzyme yielded 10 fragments totalling 2,570 bp. By three criteria, electron-microscopy, Eco R1 and Hae digestion, we conclude that the heavy MtDNA isolated from senescent cultures of Podospora anserina consisted of a monomeric tandemly repeating subunit of about 2,600 bp length.These results on the properties of senescent MtDNA are discussed with regard to the published properties of the rho
- mutation in the yeast, S. cerevisiae. 相似文献
92.
93.
Using a number of intrafamilial PLTs raised against identical HLA haplotypes it has been possible to construct a model in an informative family defining the HLA-D region as a genetic system. This system consists of at least two regions separated by a recombination between HLA-D and GLO. In relation to the site of recombination, a minimum of one centromeric and three telomeric components can be identified per haplotype.—Fourteen PLTs raised and defined within the family were subsequently tested in a Caucasian population (n=84) and in 13 unrelated, complete families.—It is concluded that the hypothetical model proposed for the HLA-D region as a genetic system of linked loci, coding at the cell surface for associated but distinct components (at least four per haplotype), allows for typing of the components of the HLA-D system of any given haplotype. Serological typing of HLA-D components should, in the near future, provide a more convenient way of establishing component phenotypes than the present use of primed lymphocyte typing reagents. Among the components isolated, some have a high association with the classic alleles defined either by homozygous typing cells or DR serology. Others form the basis of cross-reactivity but their presence does not interfere with standard typing. Others, however, seem by their mere presence to be responsible for false assignments.—The concept of HLA-D as a genetic system clarifies many of the inconsistencies observed with a one-locus system.Research scientists from INSERM.Research Fellow from the Danish Medical Research Council.Central Blood Bank — Marseille 相似文献
94.
Summary
Sobolevicanthus dlouhyi n. sp. is close to S. krabbeella but differs from it firstly by the longer rostellar hooks (83–85 m instead of 56–64 m). The cirrus pouch is shorter in the new species, no longer than the width of the widest proglottis, whereas in S. krabbeella it is twice as long. ac]19810312 相似文献
95.
The measurement of the intrinsic alkaline Bohr effect of various human haemoglobins by isoelectric focusing 下载免费PDF全文
We have used isoelectric focusing to measure the differences between the pI values of various normal and mutant human haemoglobins when completely deoxygenated and when fully liganded with CO. It was assumed that the ΔpI(deox.–ox.) values might correspond quantitatively to the intrinsic alkaline Bohr effect, as most of the anionic cofactors of the haemoglobin molecule are `stripped' off during the electrophoretic process. In haemoglobins known to exhibit a normal Bohr coefficient (ΔlogP50/ΔpH) in solutions, the ΔpI(deox.–ox.) values are lower the higher their respective pI(ox.) values. This indicates that for any particular haemoglobin the ΔpI(deox.–ox.) value accounts for the difference in surface charges at the pH of its pI value. This was confirmed by measuring, by the direct-titration technique, the difference in pH of deoxy and fully liganded haemoglobin A0 (α2β2) solutions in conditions approximating those of the isoelectric focusing, i.e. at 5°C and very low concentration of KCl. The variation of the ΔpH(deox.–ox.) curve as a function of pH (ox.) was similar to the isoelectric-focusing curve relating the variation of ΔpI(deox.–ox.) versus pI(ox.) in various haemoglobins with Bohr factor identical with that of haemoglobin A0. In haemoglobin A0 the ΔpI(deox.–ox.) value is 0.17 pH unit, which corresponds to a difference of 1.20 positive charges between the oxy and deoxy states of the tetrameric haemoglobin. This value compares favourably with the values of the intrinsic Bohr effect estimated in back-titration experiments. The ΔpI(deox.–ox.) values of mutant or chemically modified haemoglobins carrying an abnormality at the N- or C-terminus of the α-chains are decreased by 30% compared with the ΔpI value measured in haemoglobin A0. When the C-terminus of the β-chains is altered, as in Hb Nancy (α2βTyr-145→Asp2), we observed a 70% decrease in the ΔpI value compared with that measured in haemoglobin A0. These values are in close agreement with the estimated respective roles of the two major Bohr groups, Val-1α and His-146β, at the origin of the intrinsic alkaline Bohr effect [Kilmartin, Fogg, Luzzana & Rossi-Bernardi (1973) J. Biol. Chem. 248, 7039–7043; Perutz, Kilmartin, Nishikura, Fogg, Butler & Rollema (1980) J. Mol. Biol. 138, 649–670]. In other mutant haemoglobins it is demonstrated also that the ΔpI(deox.–ox.) value may be decreased or even suppressed when the substitution affects residues involved in the stability of the tetramer. These results support the interpretation proposed by Perutz, Kilmartin, Nishikura, Fogg, Butler & Rollema [(1980), J. Mol. Biol. 138, 649–670] for the mechanism of the alkaline Bohr effect, and also indicate that the transition between the two quaternary configurations is a prerequisite for the full expression of the alkaline Bohr effect. 相似文献
96.
Clerosterol-[26-14C], a 24β-ethyl-25-methylene sterol [(24S)-24-ethylcholesta-5,25-dien-3β-ol], was incorporated into clionasterol and poriferasterol by cultures of the green algae Trebouxia sp. 213/3 and Trebouxia sp. 219/2. Degradation of the labelled poriferasterol showed that the 14C retained its identity and was not incorporated as a result of metabolism of the clerosterol-[26-14C] and randomisation of label. These results are consistent with the proposed production, and subsequent reduction, of a 24β-ethyl-25-methylene intermediate in 24β-ethyl sterol biosynthesis in algae of the order Chlorococcales. 相似文献
97.
Catherine Richard Claude Delaude Louisette Le Men-Olivier Jean Le Men 《Phytochemistry》1978,17(3):539-541
The structure of a new bisindole alkaloid has been elucidated by chemical correlation and analysis of 13C NMR spectra. 相似文献
98.
Lieve de Clercq Claude Remacle Jean Demal 《In vitro cellular & developmental biology. Plant》1977,13(2):85-90
Summary The use of a semi-natural medium (Eagle’s MEM supplemented with chicken embryo extract) appears to be satisfactory for ovarian
and testicular fragment cultures ofCarassius auratus. The male germ cells show a normal degeneration which might be attributed to a lack of pituitary hormones: gonadotropic and,
possibly, somatotropic hormone. The ovarian fragments maintain a normal organization during 21 days of culture. Only the occytes
in late vitellogenesis massively atresiate at the beginning of culture. The addition of fetal bovine serum to this medium
produces surprising effects on the testicular explants, particularly on the spermatogonial mitoses. This might be attributed
to the presence of STH and androgen in the serum. The modifications of ovarian explants, on the other hand, are identical
to those observed with Eagle’s MEM supplemented with chicken embryo extract. M 199 has been tested as a synthetic medium;
the preliminary results are encouraging. Testosterone, when added to the semi-natural medium, permits complete spermatogenesis
in the testicular fragments during the 21 days of culture, but does not produce any effect on the ovarian explants. 相似文献
99.
Claudine Grégori Claude Besmond Axel Kahn Jean-Claude Dreyfus 《Biochemical and biophysical research communications》1982,104(2):369-375
High molecular weight cellular RNA was isolated from adult and fetal human liver tissue by a procedure of ethanol precipitation in concentrated guanidine-HCl solutions. About 5 mg of RNA were obtained from one gram of liver. RNA was fractionated by sucrose gradient ultracentrifugation. Aldolase B neosynthesized in a reticulocyte lysate cell-free system under the direction of total or fractionated RNA was purified by immunoaffinity microchromatography. Messenger RNA specifying synthesis of aldolase B exhibited a sedimentation coefficient of 16 S both in adult and fetal liver. This enzyme represented 1.3 % of the total neosynthesized proteins in adult liver, 0.1 % in the liver of a 6-month-old fetus and less than 0.01 % in the liver of a 4.5 month-old fetus. 相似文献
100.
Heinz Egge Jean Claude Michalski Gerard Strecker 《Archives of biochemistry and biophysics》1982,213(1):318-326
Three oligosaccharides isolated from the urine of a patient suffering from mannosidosis, a Man9GlcNAc, a Man8GlcNAc, and a Man7GlcNAc, were analyzed by electron impact mass spectrometry at 20 eV after reduction with NaB2H4 and permethylation. Molecular ions were observed at 2144, 1940, and 1736, respectively. In the high-mass range very intense ions were found at M-45. The mass spectrum of the homogenous decasaccharide Man9GlcNAc1D contains ions that could be attributed to specific parts of each of the three antennae of the molecule. Thus characteristic key ions were recognized. With the aid of these key ions the spectra of the nona- and octasaccharide mixtures could be evaluated in a qualitative and a semiquantitative way. In the nonasaccharide all three possible isomers that can be produced by cleavage of one of the three terminal α-mannoses are present, although in differing amounts. However, only five of the six possible isomers of the octasaccharide could be detected. 相似文献