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61.
T. N. Naumova J. V. Osadtchiy V. K. Sharma P. Dijkhuis K. S. Ramulu 《Protoplasma》1999,208(1-4):186-195
Summary Data on structural and functional aspects of mitotic diplospory and later stages of apomictic seed formation are reported forPoa palustris andP. nemoralis. In this study, the plant material of two Russian populations ofP. nemoralis andP. palustris were used for transmission electron microscope observations. Seed formation was investigated by phase contrast microscopy in two populations ofP. nemoralis collected in The Netherlands. The processes of transformation of the megasporocytes to the megaspore mother cells of diplosporous embryo sacs, and thereafter to one- and two-nucleate diplosporous embryo sacs (Antennaria type) were characterized by an increase of cell size, structural and functional reorganization of the nucleus, nucleolus, and cytoplasm, and cell isolation as a result of thickening of the cell wall. These were accompanied by an increase in the cell metabolic activity inferred from visual evidence of the activation of nucleus, nucleolus, endoplasmic reticulum, dictyosomes, mitochondria, and from the appearance of a dense population of ribosomes and polysomes. The diplosporous embryo sac of the Antennaria type was characteristic for bothP. nemoralis andP. palustris. No signs of the presence of synaptonemal complexes were observed during the process of diplosporous-embryo-sac megaspore mother cell differentiation and division. About 90–95% of the diploid egg cells of diplosporous embryo sacs were able to produce apomictic embryos. These embryos developed before anthesis. However, many of them degenerated at the globular stage because of lack of endosperm. The ultrastructural events occurring during the process of diplospory of apomictic species, and meiosis and megagametogenesis of sexually reproduced plants are discussed.Abbreviations DMC
megaspore mother cell of diplosporous embryo sac
- TEM
transmission electron microscopy
- ER
endoplasmic reticulum 相似文献
62.
A S Shashkov N V Potekhina I B Naumova L I Evtushenko G Widmalm 《European journal of biochemistry》1999,262(3):688-695
The cell walls of Actinomadura viridis contain poly(glycosylglycerol phosphate) chains of complex structure. On the basis of NMR spectroscopy of the polymer and glycosides thereof the following structural units were found: beta-D-Galp3Me-(1-->4)[beta-D-Glcp-(1-->6)]-beta-D-Galp-(1-->1)-++ +snGro (G1); beta-D-Galp-(1-->4)-beta-D-Galp-(1-->1)-snGro (G2); beta-D-Galp3Me-(1-->4)-beta-D-Galp-(1-->1)-snGro (G2a); beta-D-Galp-(1-->1)-snGro (G3); beta-D-Galp-(1-->1)[beta-D-Galp-(1-->2)]-snGro (G4); beta-D-Glcp-(1-->2)-snGro (G5). Glycosides G1, G2 and G3 were the predominant components of the teichoic acid: they formed the polymer chain via phosphodiester bonds involving C-3 of the glycerol residue and C-3 of the galactosyl residue which in turn glycosylates C-1 of the glycerol residue. Whether the different glycosides make up the one chain or whether there are several poly(glycosylglycerol phosphate) chains in the cell wall remains to be determined. It was suggested that the minor component G5 is located at the nonterminal end of the chains. Compound G4 which contains disubstituted glycerol residues (unusual for the teichoic acid) was also found as a minor component; this may be the glycoside of a new type of teichoic acid, or a glycoside on the terminal end of the above mentioned chains. In addition, small amounts of 1,3-poly(glycerol phosphate) chains were found in the cell wall. 相似文献
63.
Molecular karyotyping and Southern blot hybridization were used to investigate chromosomal polymorphism of the LAC genes controlling lactose fermentation in Kluyveromyces marxianus strains isolated from various dairy products and natural sources in Russia and CIS countries. Profound polymorphism of karyotype patterns and accumulation of LAC genes were observed in dairy K. marxianus strains. K. marxianus strains isolated from dairy products intensively fermented lactose at 37°C after one day of cultivation, while non-dairy strains exhibited delayed lactose fermentation or did not ferment it at all. Based on the fermentation tests, twelve K. marxianus strains were selected, which are of interest as potential probiotic microorganisms suitable for further molecular genetic studies and breeding. 相似文献
64.
Z. I. Krutetskaya L. S. Milenina A. A. Naumova S. N. Butov V. G. Antonov A. D. Nozdrachev 《Doklady. Biochemistry and biophysics》2017,474(1):162-164
Using Fura-2AM microfluorimetry, it was shown for the first time that neuroleptic chlorpromazine causes intracellular Ca2+ concentration increase in macrophages due to Ca2+ mobilization from intracellular Ca2+ stores and subsequent Ca2+ entry from the external medium. Chlorpromazine-induced Ca2+ entry is inhibited by La3+ and 2-aminoethoxydiphenyl borate and is associated with Ca2+ store depletion. 相似文献
65.
A comparative molecular genetic study of 37 Kluyveromyces strains of different origin has made it possible to find molecular markers that can differentiate between the dairy yeast Kluyveromyces lactis var. lactis and the genetically close wild Kl. lactis strains from the European “krassilnikovii” population, which are unable to ferment lactose. A restriction fragment length polymorphism analysis of the IGS2 rDNA region reveals two different AluI profiles, one of which corresponds to Kl. lactis var. lactis while the other corresponds to yeasts from the “krassilnikovii” population. The AluI restriction profile of the IGS2 region of the rDNA also makes it possible to differentiate between the physiologically similar species Kl. marxianus and Kl. lactis. The origin of clinical Kl. lactis var. lactis isolates is discussed.__________Translated from Mikrobiologiya, Vol. 74, No. 3, 2005, pp. 387–393.Original Russian Text Copyright © 2005 by Naumova, Sukhotina, Naumov. 相似文献
66.
Naumova E Panchev P Simeonov PJ Mihaylova A Penkova K Boneva P Marinova D Paskalev E Simeonov PL Zlatev A 《Cell and tissue banking》2008,9(4):337-342
The transplantation program in Bulgaria started in 1968 with renal transplantations to a child and adult woman. In 1986 the
first heart transplantation was performed. To date a total of 10 heart transplants have been performed, including one combined
heart/lung. A liver transplantation program was launched in 2005 with a total number of 16 transplantations—7 from living
donors and 9 from deceased donors. The highest transplantation activity is registered in the field of renal transplantation.
During the period 1980–2006, 462 Bulgarian recipients of kidney were transplanted in Bulgaria. The ratio between transplantations
from deceased and living related donors is approximately 1:0.9. Annual transplantation activity varies among the years from
1 to 12 renal transplantations p.m.p./per year. The 1- (80.7% vs. 63.1%), 5- (57.86% vs. 39.0%) and 10-year (42.65% vs. 23.62%)
graft survival rates are higher for recipients of living donor kidneys compared to those of deceased donor. In 1983 a National
kidney waiting list was established. Currently the number of the registered patients eligible for renal transplantation is
885. The proportion of sensitized patients in the waiting list is 20.45% and 4.34% of them are hyperimmunized. Recently HLAMatchmaker
program has been implemented not only for sensitized patients but also for those with rare alleles and haplotypes. Post-transplant
immunological monitoring showed a strong association between alloantibody presence and delayed graft function (Chi-square = 10.73,
P < 0.001), acute rejection (Chi-square = 14.504, P < 0.001), chronic rejection (Chi-square = 12.84, P < 0.001) and graft loss (Chi-square = 20.283, P < 0.001). Based on the experience in our transplant center a strategy for improvement of long-term renal graft survival was
developed and implemented. 相似文献
67.
Recently Bulgarian Bone Marrow Donors Registry (BBMDR) has been established and since August 2005 it has been a member of
Bone Marrow Donors Worldwide. Currently the number of healthy donors included in the BBMDR is relatively low. All donors included
in the BBMDR are typed for HLA-A, -B, -DRB loci. Phylogenetic analysis based on HLA allele frequencies shows that Bulgarians
were characterized with closest genetic similarity to Macedonians, Greeks, Romanians, Cretans and Sardinians in comparison
to the other European and Mediterranean populations. On the contrary the second largest ethnic minority–the Roma were the
closest to the other Roma populations and North Indians. These differences were due to the predominance of alleles and haplotypes
that are specific for the Asian and the other Roma populations. These specific genetic profiles in the Bulgarian ethnic minorities
justify the need of an adequate representation of minorities in BBMDR. Future directions for BBMDR development are discussed,
including an increase of the total number of donors and these for ethnic minorities, as well the enhancement of the level
of resolution of the HLA typing for the donors in the registry. 相似文献
68.
Shi Yu Tillmann Falck Anneleen Daemen Leon-Charles Tranchevent Johan AK Suykens Bart De Moor Yves Moreau 《BMC bioinformatics》2010,11(1):309
Background
This paper introduces the notion of optimizing different norms in the dual problem of support vector machines with multiple kernels. The selection of norms yields different extensions of multiple kernel learning (MKL) such as L ∞, L 1, and L 2 MKL. In particular, L 2 MKL is a novel method that leads to non-sparse optimal kernel coefficients, which is different from the sparse kernel coefficients optimized by the existing L ∞ MKL method. In real biomedical applications, L 2 MKL may have more advantages over sparse integration method for thoroughly combining complementary information in heterogeneous data sources. 相似文献69.
70.
Naumov YN Naumova EN Yassai MB Gorski J 《Journal of immunology (Baltimore, Md. : 1950)》2011,186(11):6617-6624
The aging of T cell memory is often considered in terms of senescence, a process viewed as decay and loss of memory T cells. How senescence would affect memory is a function of the initial structure of the memory repertoire and whether the clonotypes that make up the repertoire decay at random. We examine this issue using the T cell memory generated to the conserved influenza A epitope M1(58-66), which induces a strong, focused, but polyclonal CD8 T cell response in HLA-A2 individuals. We analyzed the CD8 T cell memory repertoires in eight healthy middle-aged and eight healthy older blood donors representing an average age difference of ~ 27 y. Although the repertoires show broadly similar clonotype distributions, the number of observable clonotypes decreases significantly. This decrease disproportionally affects low-frequency clonotypes. Rank frequency analysis shows the same two-component clonotype distribution described earlier for these repertoires. The first component includes lower frequency clonotypes for which distribution can be described by a power law. The slope of this first component is significantly steeper in the older cohort. Generating a representative repertoire for each healthy cohort allowed agent-based modeling of the aging process. Interestingly, simple senescence of middle-aged repertoires is insufficient to describe the older clonotype distribution. Rather, a selective clonotype expansion must be included to achieve the best fit. We propose that responses to periodic virus exposure may drive such expansion, ensuring that the remaining clonotypes are optimized for continued protection. 相似文献