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971.
A. F. Croes J. M. J. M. Steijns Geertrui J. M. L. De Vries Tonneke M. J. A. van der Putte 《Planta》1978,141(2):205-209
Meiosis and sporogenesis in yeast are completely blocked by ammonia added in low concentration (10 mM) to the sporulation medium. Premeiotic DNA synthesis is not initiated in the presence of ammonium ions. The inhibitor interferes with protein turnover by reducing both synthesis and breakdown. The in vitro activities of proteinases A and B in sporulation medium supplemented with ammonia are much lower than in the control. This may partially explain the effect of ammonium ions on protein metabolism in vivo.Abbreviations PSP
presporulation medium
- SPM
sporulation medium 相似文献
972.
973.
974.
M-mode echocardiograms of two patients with bacterial endocarditis of approximately 4 months' duration showed dense echoes in the area of the aortic valve. In one patient, who had no prior abnormal cardiac findings, the echoes were clearly suggestive of valvular vegetations. The second patient, however, was known to have had aortic valve disease and a systolic murmur for more than a decade; therefore, dense echoes arising from the aortic valve also could have resulted from valvular calcification. In both patients, cross-sectional echocardiography provided important information. In the first patient, retrograde cardiac catheterization was prevented by large and highly mobile masses attached to the aortic cusps that prolapsed into the left ventricular outflow tract during diastole. Aortic valve replacement without further hemodynamic evaluation was recommended. In the second patient, whose blood cultures remained negative after the acute phase of his illness had been treated, cross-sectional echocardiography showed large vegetations on the aortic valve. Intraoperative findings confirmed the echocardiographic interpretation in each case. 相似文献
975.
Serological studies relating F9 antigen of embryonal carcinoma cells to
at the murineT/t complex have been extended and confirm that only the lethal haplotype t12- and none of the other five lethal haplotypes-affects the quantitative expression of F9 antigen on sperm. Cytotoxicity tests on preimplantation embryos show that t12 homozygotes are less susceptible to antiF9 serum than tw5 homozygotes, and that using specific antimutant haplotype antisera prepared against sperm, t12 antigen is detectable on morulae, whereas tw5 antigen is not. 相似文献
976.
The topographical distribution of genetically defined alloantigens of the bovine erythrocyte was investigated by a serological absorption procedure known as the blocking test. Blocking was observed between the E′1 and Y2 antigens in theB system when these occurred in the same phenogroup. E′1 was also blocked by G and Q′ in the same phenogroup and Y2 was blocked by G. No blocking was observed between specificities residing either in different phenogroups or in different systems. We conclude that the several specificities in a givenB-system phenogroup are carried on a single molecule having multiple antigenic determinants, and that this arrangement is entirely consistent with the hypothesis that these factors are controlled by multiple alleles at a single locus. 相似文献
977.
978.
From data obtained by differential scanning calorimetry phase diagrams were constructed, using a thermodynamically based fitting method. The following binary mixtures of phosphatidylcholines in water were studied: 14:0/ 14:0-glycerophosphocholine/16:0/16:0-glycerophosphocholine, 14:0/14:0-glycerophosphocholine /18:0/18:0-glycerophosphocholine, 12:0/12:0-glycerophosphocholine /16:0/16:0-glycerophosphocholine, 18:1t/18:1t-glycerophosphocholine /14:0/14:0-glycerophosphocholine and 18:1t/18:1t-glycerophosphocholine /16:0/16:0-glycerophosphocholine.A comparison is made of the present results with those obtained using probe techniques and the differences are discussed. 相似文献
979.
Electric birefringence measurements of suspensions of T3 and T7 bacteriophages in 10?2 M phosphate buffer, pH 6.9, show that there is a difference in their rotational diffusion coefficient. The values corrected to 25°C and water viscosity are D25,w = 4630 ± 130 sec?1 and D25,w = 5290 ± 260 sec?1 for T3 and T7, respectively. The value obtained from shell model calculations (according to Filson and Bloomfield) is D25,w = 4500 ± 600 sec?1. The apparent permanent dipole moments are 4.5 × 10?26 C·m and 1.7 × 10?26 C·m for T3 and T7, respectively. For both phage particles the intrinsic optical anisotropy is +7.2 × 10?3. It is shown that this anisotropy is mainly due to the DNA molecule inside the head of the phage. Its positive value means that there exists an excess orientation of the DNA helix perpendicular to the symmetry axis of the particle. For T7 an unexpectedly large increase of Δns and Ksp occurs at a glycerol concentration of about 30% (v/v). This increase is interpreted as being caused by a change of the shape of the particle and/or a change in the secondary structure of the DNA inside the head of the bacteriophage. 相似文献
980.
Summary Cell suspensions of the fresh-watersponge Ephydatia fluviatilis have been fractionated by means ofFicoll gradient centrifugation. Three fractions were isolated. The densest contains archeocyte-like cells only; the intermediate fraction is very rich in choanocytes, and the lightest is a mixture of cell types. Earch fraction shows specificaggregative properties and potentialities to reconstitute functional sponges.It appears that the sequence of reconstitution events can be selectively altered by certain disequilibria in the cell populationThese preliminary results constitute a first approach to the analysis ofcell type specificity in sponges. 相似文献