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991.
The mass per unit length of
and the corresponding DNA packing ratio of about 14 for the chromatin soluble at moderate ionic strengths has been determined by light scattering. With the increase in ionic strength and corresponding release of histone H1 the DNA packing ratio has been found to decrease down to 4.4. The data obtained are consistent with the idea suggested previously that the salt-soluble chromatin is organized in double nucleosome chains arranged side-by-side and stabilized by H1. With salt-induced H1 release the double chain dissociates and the nucleosomal DNA partially unravels. 相似文献
992.
993.
Sundquist Bo Jönsson Lennart Jacobsson Sten-Olof Hammarberg Karl-Erik 《Acta veterinaria Scandinavica》1981,22(3-4):315-330
A progressive paresis was encountered in herds of Swedish goats. The symptoms developed during a period of weeks or months, and were initially often seen as a weakness of the hind limbs before the animals became paralytic. The development and the histopathological lesions of the disease in the GNS and the lungs were similar to those of visna in sheep. In vitro grown choroid plexus cells, prepared from affected goats, showed foci of polykaryocytes. Electron microscopy revealed the presence of particles morphologically similar to those of sheep visna virus (SVV). Goats experimentally infected with the goat visna virus (GVV) developed GNS lesions similar to those of visna in sheep and became seropositive to SVV. The results of complement fixation tests, carried out on sera from 11 goat herds, showed a coincidence between seropositiveness and the occurrence of disease in one and the same herd. Using the ELISA method, an average of 80 % of the goats in 5 herds were found to be seropositive to GVV. 相似文献
994.
The prenatal effects of mycotoxins were investigated in GBA mice given by stomach tube a single dose of either aflatoxin B1 (4 mg/kg), ochratoxin A (8 mg/kg) or zearalenone (20 mg/kg) on pregnancy day 8 or 9. Aflatoxin caused foetal anomalies (exencephaly, open eyes, and protrusion of intestines) after exposure on gestation day 8 but not on day 9. The effects (increased prenatal mortality, reduced foetal growth, and a wide variety of malformations) caused by ochratoxin were much more severe and occurred after treatment on either of the 2 days of gestation. Among the spectrum of malformations, predominantly involving the craniofacial complex and the axial skeleton, the most striking was the total aplasia/dysplasia of the upper facial structures. These defects were always accompanied by exencephaly and anophthalmia. Zearalenone caused no effects. It is concluded that of the 3 mycotoxins screened with the technique used, ochratoxin is the most potent teratogen in mice. 相似文献
995.
Werner Hönig Christian Wandrey Maria-Regina Kula 《Applied microbiology and biotechnology》1977,3(4):245-256
Summary -Glucosidase isolated from brewer's yeast (Saccharomyces carlsbergensis) was immobilized using hydroxymethacrylate activated by cyanogen bromide as a carrier. Up to a hundred-fold increase in the stability of the enzyme was observed after immobilization. The yield in activity (bound/applied) was up to 30%. Before developing the process of enzymatic cleavage of maltose further we evaluated the kinetic properties of the enzyme catalyst, as we had observed earlier that the soluble enzyme is strongly inhibited by the product glucose. This is even more pronounced with the immobilized -glucosidase leading in this case to a linear relation between initial rate and substrate concentration, so KM (approx.) values can no longer be defined due to the dominating influence of the product inhibition. 相似文献
996.
Summary A comparison of citric acid fermentations in manganese-deficient and manganese-containing media showed that manganese strongly influences idiophase metabolism. In the presence of manganese, cell growth increases, sugar consumption is diminished and acidogenesis decreases drastically. An investigation of the key enzymes of glycolysis, the pentosephosphate pathway, TCA-cycle, nitrogen metabolism, and gluconeogenesis indicated that manganese deficiency was accompanied by a repression of anabolic and TCA-cycle-enzymes with the exception of citrate synthase. The activity of this enzyme and the enzymes of glycolysis paralleled the sugar consumption rate. In the presence of manganese, no repression of enzyme synthesis was observed. Activities of 2-oxoglutarate dehydrogenase and isocitrate lyase could not be detected in either case. The results support the hypothesis that manganese deficiency mainly affects the operation of biosynthetic reactions inAspergillus niger, thus leading to an overflow of citric acid as an end product of glycolysis. 相似文献
997.
Summary Radioactive decay in a labelled molecule leads to specific chemical and biological consequences which are due to local transmutation effects such as recoil, electronic excitation, build-up of charge states and change of chemical identity, as well as to internal radiolytic effects. In the present paper these effects are reviewed emphasizing the relation of the chemical alterations on a molecular level to the biological manifestation. Potential importance of this type of research for biomedical applications is pointed out. In part 1 we review the underlying physical and chemical principles and consequences of -decay of3H,14C,32P,33P,35S and125I for gaseous and simple condensed organic systems. Part 2 which will appear in the next issue will include the discussion of biological effects associated with -decay. 相似文献
998.
Three multiple phycoerythrin-545 forms were purified from crude extracts of Cryptomonas maculata by preparative isoelectric focusing. The phycoerythrin forms are charge isomers with isoelectric points at 7.83, 5.05 and 4.84. The multiple pigment forms have similar molecular weights of 44500 daltons and are composed of subunits of unequal size in a 1:1 stoichiometry with molecular weights of () 9900 and () 15700 daltons, twice. The proposed quarternary structure of the native pigments is ()2()2.The charge differences of the phycoerthrins are caused by a charge heterogeneity of the light subunits, as revealed by urea gel electrophoresis. The chains of pigment form pI 7.83 had a greater electrophoretic mobility than those subunits of the acidic pigment forms pI 5.05 and pI 4.84.The phycoerythrin forms have an absorption spectrum with similar absorption maxima at 544 nm, but differ in the position of the long wavelength shoulders lying at 555 and 557 nm in the negatively charged pigment forms and at 560 nm for the phycoerythrin form with a pI at 7.83.The fluorescence emission spectra coincide in their asymmetrical shape with shoulders at about 620 nm; they slightly differ int he position of the emission maxima at 586 nm for the phycoerythrins with pIs at 4.84 and 5.05 and at 584 nm for phycoerythrin with pI at 7.83.Abbreviations PC
phycocyanin
- PE
phycoerythrin
- pI
isoelectric point
- SDS
sodium dodecyl sulphate 相似文献
999.
Recording from multiple electrodes at different sites along a peripheral nerve permits the application of powerful filtering methods to extract the activity of populations of fibres within the nerve which differ in temporal or spectral characteristics. The design of optimal linear filters is initially treated as a general problem in the calculus of variations in which the signals from one population of nerve fibres are extracted so as to minimize those from a second population of nerve fibres or from other sources (noise). A particularly important application arises when the signals at two electrodes are related by weighting functions. In the simplest example the weighting function represents the time delay for nerve impulses to conduct from one electrode to the other, but explicit results are also derivable when there are a range of conduction delays with probabilities distributed according to well-known functions such as the sinc2 function.This work was partially supported by the National Research Council of Canada and Medical Research Council of Canada by Grant NRC A-4345 to MNO and Grant MRC MA-3307 to RBS through the University of Alberta 相似文献
1000.
Summary In an attempt to stimulate fetal cells in the maternal blood to mitotic division, peripheral blood lymphocytes were cultured from ten primiparous women and six multiparous women. In the case of the ten primiparous women, PWM was used to stimulate lymphocytes in 3- and 7-day cultures made at the 16th, 20th, 24th, and 28th week of gestation. Altogether, 10565 mitoses were analyzed after quinacrine staining of cells from five mothers who each subsequently gave birth to a male infant, and not a single XY mitosis was found.In the case of the multiparous women, lymphocyte cultures, with PHA or LPS as mitogen and MLC, were initiated between the 13th and 20th week of pregnancy. Four of the mothers were pregnant with a male child, and two with a female child. From cultures of each of the four mothers expecting a boy, a total of 9721 mitoses were analyzed after quinacrine staining, and not a single XY mitosis was found. However, one XY cell was found in the culture from one of the two women who delivered a girl. The XY mitosis probably originated from a pregnancy 8 months earlier which terminated in a male infant.In an attempt to culture and obtain good chromosome preparations from small numbers of cells, it was shown that a good mitotic response and good chromosome preparations could be obtained from as few as 6000 lymphocytes. 相似文献