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1.
Tarján M 《Magyar onkologia》2002,46(4):315-321
This review deals with results attained by Hungarian authors in the field of sentinel nodes and presents the current status of sentinel lymphadenectomy in Hungary. After a short historical overview, results with melanoma and breast cancer are summarized, and feasibility studies on other possible sites (gastrointestinal tract, thyroid gland) are also mentioned. Pathological aspects are also dealt with in a separate section. The summary of these results suggests that Hungarian authors have investigated several facets of sentinel node biopsy, their results are in keeping with international results. Despite the favourable results, the method still needs time to be more widely accepted and reflected in the literature.  相似文献   

2.
F Zou  B S Yandell  J P Fine 《Genetics》2001,158(3):1339-1346
We consider some practical statistical issues in QTL analysis where several crosses originate in multiple inbred parents. Our results show that ignoring background polygenic variation in different crosses may lead to biased interval mapping estimates of QTL effects or loss of efficiency. Threshold and power approximations are derived by extending earlier results based on the Ornstein-Uhlenbeck diffusion process. The results are useful in the design and analysis of genome screen experiments. Several common designs are evaluated in terms of their power to detect QTL.  相似文献   

3.
Agents that elevate intracellular cAMP levels are required for growth of many cell types in culture including normal rat mammary epithelial (RME) cells. To determine if the intracellular levels of cAMP that result from stimulation by agents such as cholera toxin (CT) or prostaglandin E-1 (PGE-1) are within the physiological range, cAMP levels were determined in RME cells growing in primary culture and compared to levels measured in freshly isolated mammary epithelium. The results indicate that the cAMP levels of mammary epithelial organoids obtained from 45-day-old virgin rats are 4 to 6 pmol/10(6) cells. Growth of RME cells in primary culture in the presence of CT results in cAMP levels of approximately 15 to 20 pmol/10(6) cells early in culture when cells are proliferating rapidly. As cells approach confluence, cAMP concentrations decrease to levels observed in fresh organoids. CT-stimulated cAMP levels appear to be within the range of those found in pregnant mammary epithelium in vivo. Growth of RME cells in medium supplemented with PGE-1 instead of CT results in cAMP levels equivalent to those found in fresh mammary epithelial organoids and under these conditions the growth rate is approximately half that found in CT-stimulated cells. These results indicate cAMP to be a positive regulator of cell growth in vivo at levels that are within the physiological range.  相似文献   

4.
The results of stereotactic pallidotomy in 37 patients with extrapyramidal disorders are presented. All patients had the same RF lesions and target coordinates. The patients are classified into 5 groups according to the clinical picture. These results are compared with those obtained by thalamotomy in a similar group of patients. The main indications for pallidotomy are given. The spatial representation of globus pallidus medialis according to Andrews and Watkins, Talairach and the author are shown and their differences discussed.  相似文献   

5.
The solution structure and dynamics of sucrose are examined using a combination of NMR residual dipolar coupling and molecular mechanics force fields. It is found that the alignment tensors of the individual rings are different, and that fitting 35 measured residual dipolar couplings to structures with specific phi, psi values indicates the presence of three major conformations: phi, psi=(120 degrees ,270 degrees), (45 degrees, 300 degrees) and (90 degrees ,180 degrees). Furthermore, fitting two structures simultaneously to the 35 residual dipolar couplings results in a substantial improvement in the fits. The existence of multiple conformations having similar stabilities is a strong indication of motion, due to the interconversion among these states. Results from four molecular mechanics force fields are in general agreement with the experimental results. However, there are major disagreements between force fields. Because fits of residual dipolar couplings to structures are dependent on the force field used to calculate the structures, multiple force fields were used to interpret NMR data. It is demonstrated that the pucker of the fructofuranosyl ring affects the calculated potential energy surface, and the fit to the residual dipolar couplings data. Previously published 13C nuclear relaxation results suggesting that sucrose is rigid are not inconsistent with the present results when motional timescales are considered.  相似文献   

6.
Results are presented from experimental and theoretical investigations of oscillatory and wave phenomena observed in the edge region in the U-3M torsatron during plasma creation and heating by an RF discharge in the ICR frequency range, accompanied by a transition to improved confinement. The main results are reported of diagnostic measurements of the spectral composition of oscillations, as well as of how the phase and amplitude relationships depend on time and on the RF power during its injection into the plasma. The measurements were carried out with electrostatic probes positioned at the edge of the plasma confinement region. The experimental results are interpreted using the kinetic theory of the electron-ion parametric instability of a plasma in the ion cyclotron frequency range and are compared with the results of numerical simulations.  相似文献   

7.
Community extinction patterns in coloured environments   总被引:1,自引:0,他引:1  
Understanding community responses to environmental variation is a fundamental aspect of ecological research, with direct ecological, conservation and economic implications. Here, we examined the role of the magnitude, correlation and autocorrelation structures of environmental variation on species' extinction risk (ER), and the probability of actual extinction events in model competitive communities. Both ER and probability increased with increasing positive autocorrelation when species responded independently to the environment, yet both decreased with a strong correlation between species-specific responses. These results are framed in terms of the synchrony between--and magnitude of variation within--species population sizes and are explained in terms of differences in noise amplification under different conditions. The simulation results are robust to changes in the strength of interspecific density dependence, and whether noise affects density-independent or density-dependent population processes. Similar patterns arose under different ranges of noise severity when these different model assumptions were examined. We compared our results with those from an analytically derived solution, which failed to capture many features of the simulation results.  相似文献   

8.
D J Thomas 《FEBS letters》1992,307(1):10-13
Certain concepts and misconceptions in the field of protein folding are discussed from the viewpoint of a theoretical physicist. It is argued that there can be no protein folding code and that perceived correlations between sequence or composition and three-dimensional structure are more likely to be an artefact of a limited database than a real result. Attempts at using molecular dynamics algorithms are also likely to produce artefactual results because results depend critically on the unknown hamiltonian energy function. Correct calculations of configurational entropy are thought to be the most likely next step in understanding how and why proteins fold.  相似文献   

9.
In albino rats, as in other mammals, nucleoli with nucleolonemata and compact nucleoli in the stem cells of the erythrocyte and granulocyte series are progressively replaced during maturation and differentiation first by ring shaped nucleoli and then by micronucleoli with low and finally with inhibited RNA synthesis. There are, however, differences between the nucleolar coefficient values and the proportion of ring shaped nucleoli and micronucleoli in maturing neutrophils in the albino rat, the mouse and man. In the case of the erythroblasts, the differences between the proportion of various nucleolar types in the three given species are smaller. The results thus indicate that the developmental trend of nucleolar changes related to cell maturation and differentiation is the same, but that there are interspecies differences because of which the results obtained in one species cannot be applied mechanically to another, i.e. results obtained in a laboratory animal cannot be applied automatically to man.  相似文献   

10.
The lipid bilayer vesicle is a model of the cellular membrane. Even in this simple system, however, measuring the thermodynamics of membrane protein association is a challenge. Here we discuss Forster resonance energy transfer (FRET) in liposomes as a method to probe the dimerization of transmembrane helices in a membrane environment. Although the measurements are labor intensive, FRET in liposomes can be measured accurately provided that attention is paid to sample homogeneity and sample equilibration. One must also take into account statistical expectations and the FRET that results from random colocalization of donors and acceptors in the bilayer. Without careful attention to these details, misleading results are easy to obtain in membrane FRET experiments. The results that we obtain in model systems are reproducible and depend solely on the concentration of the protein in the bilayer (i.e., on the protein-to-lipid ratio), thereby yielding thermodynamic parameters that are directly relevant to processes in biological membranes.  相似文献   

11.
《Biomarkers》2013,18(8):677-683
Sample handling and storage conditions in specimens frozen over long periods of time can severely impact marker levels. If laboratory technologies, practices and related protocols change over time, biomarker studies are potentially biased and report erroneous results. These issues and pitfalls are often overlooked in system biology studies using previously collected and stored materials, and are likely to be one notable cause for biomarker candidates failing to be validated. We present results from simulation studies quantifying the loss in statistical power to detect true biomarkers, due to diminishing concentration of analytes in samples subject to poor handling and storage conditions.  相似文献   

12.
The perception of natural scenes relies on the integration of pre-existing knowledge with the immediate results of attentional processing, and what can be remembered from a scene depends in turn on how that scene is perceived and understood. However, there are conflicting results in the literature as to whether people are more likely to remember those objects that are consistent with the scene or those that are not. Moreover, whether any discrepancy between the likelihood of remembering schema-consistent or schema-inconsistent objects should be attributed to the schematic effects on attention or on memory remains unclear. To address this issue, the current study attempted to directly manipulate attention allocation by requiring participants to look at (i) schema-consistent objects, (ii) schema-inconsistent objects, or (iii) to share attention equally across both. Regardless of the differential allocation of attention or object fixation, schema-consistent objects were better recalled whereas recognition was independent of schema-consistency, but depended on task instruction. These results suggest that attention is important both for remembering low-level object properties, and information whose retrieval is not supported by the currently active schema. Specific knowledge of the scenes being viewed can result in the recall of non-fixated objects, but without such knowledge attention is required to encode sufficient detail for subsequent recognition. Our results demonstrate therefore that attention is not critical for the retrieval of objects that are consistent with a scene's schematic content.  相似文献   

13.
Some new results for three-step prey-predator food chains, which appear in the exactly solvable Gompertz model, are shown to follow in the Lotka-Volterra model also. Possible implications of these results are discussed.  相似文献   

14.
Malaria is probably the most serious health problem facing northern Amazonia, and isolated populations can benefit greatly from the knowledge of local resources which may effectively be used to control it. The results of an ethnobotanical survey of the plant species used in the treatment of malaria in the Brazilian State of Roraima are presented. Fieldwork was carried out amongst seven savanna-and forest-dwelling indigenous groups, and among the Luso-Brazilian population. Ninety-nine species, of 82 genera and 41 families, were identified as having been used for this purpose in the region. The results are discussed in the context of previously published information on anti-malarial plants of northern Latin America, which was analysed by a broad literature survey whose overall results are also presented here. Of the species collected in Roraima, only 24 appear previously to have been reported as anti-malarials, although 49% of the represented genera are known to be used in this way elsewhere. The plants are currently undergoing laboratory screening for anti-malarial activity and toxicity.  相似文献   

15.
This study examines the short- and long-term effects of war-induced and war-unrelated migration on fertility outcomes using data from two peri-urban municipalities of Greater Luanda in Angola. In the short term, results from multi-level discrete-time logistic regression models indicate that net of other factors, war-unrelated migration is associated with a lower probability of birth than war-induced migration in a given year. Similar results are obtained when the effects of migration are lagged by a year. At the same time, the effects of war-triggered migration do not differ significantly from those of not migrating in a given year but are statistically significant when the effects of migration are lagged by a year. In the long term, the effects of migration experience on cumulative fertility are negligible and not statistically significant net of demographic and socioeconomic variables. Interpretations of the results are offered in the context of Angola and their broader implications are reflected on.  相似文献   

16.
Results are presented from experimental studies of heat transfer in liquid-like plasma-dust structures. The experiments were performed with aluminum oxide grains ~3–5 μm in size in an RF discharge plasma. The heat capacity of the dust grains in plasma is measured. The thermal conductivity and thermal diffusivity of liquid-like plasma-dust structures are deduced under the assumption that the observed temperature gradients and the propagation of a thermal perturbation in a dusty plasma are related to heat conduction within the dust component. The measured temperature dependences of the thermal conductivity and thermal diffusivity are in qualitative agreement with the results of numerical simulations performed in the model of a simple single-atom liquid. It is shown that quantitative discrepancy between the experimental and numerical results is related to the energy loss of dust grains in their collisions with the neutral particles of the ambient gas.  相似文献   

17.
Applications of permeabilized cell and skinned fiber techniques in combination with methods of mathematical modelling for studies of mitochondrial function in the cell are critically evaluated. Mathematical models may be useful tools for explaining biological phenomena, but only if they are selected by fitting the computing results with real experimental data. Confocal microscopy has been used in experiments with permeabilized cardiomyocytes and myocardial fibers to determine the maximal diffusion distance from medium to the core of cells, which is shown not to exceed 8-10 microm. This is a principal index for correctly explaining high apparent Km for exogenous ADP (200-300 microM) in regulation of mitochondrial respiration in oxidative muscle cells in situ. The best fitting of the results of in silico studies may be achieved by using of the compartmentalized energy transfer model. From these results, it may be concluded that in cardiac muscle cells the mitochondria and ATPases are organized into intracellular energetic units (ICEUs) separated from the bulk phase of cytoplasm by some barriers which limit the diffusion of adenine nucleotides. In contrast, alternative models based on the concept of the cell as homogenous system do not explain the observed experimental phenomena and have led to misleading conclusions. The various sources of experimental and conceptual errors are analyzed.  相似文献   

18.
Environmental factors such as diet, bedding material and temperature at the time of testing affected a 'model' pharmacological response--pentobarbitone sleeping time--differentially in a range of inbred strains. These results are probably explained by variations in the responses of the strains to constituents of the diets and bedding materials used in the experiments. Differences in the results between experiments suggest that there are also fluctuations in the composition of the diets and bedding materials over time. Strain X environment interactions such as those found here may explain differences in strain rankings between experiments. They would also account for some of the variability in results found between laboratories and within a laboratory over time.  相似文献   

19.
The endodermal cells of the shoot are thought to be the gravity-sensing cells in Arabidopsis. The amyloplasts in the endodermis that sediment in the direction of gravity may act as statoliths. Endodermis-specific expression of SGR2 and ZIG using the SCR promoter could complement the abnormal shoot gravitropism of the sgr2 and zig mutants, respectively. The abnormalities in amyloplast sedimentation observed in both mutants recovered simultaneously. These results indicate that both genes in the endodermal cell layer are crucial for shoot gravitropism. ZIG encodes AtVTI11, which is a SNARE involved in vesicle transport to the vacuole. The fusion protein of SGR2 and green fluorescent protein localized to the vacuole and small organelles. These observations indicate that ZIG and SGR2 are involved in the formation and function of the vacuole, a notion supported by the results of subcellular analysis of the sgr2 and zig mutants with electron microscopy. These results strongly suggest that the vacuole participates in the early events of gravitropism and that SGR2 and ZIG functions are involved.  相似文献   

20.
In eukaryotes, autophagy is a conserved protein degradation system that degrades cytoplasmic components by encompassing them with double-membrane structures, called autophagosomes, and delivering them to the lytic compartments of vacuoles/lysosomes. Certain Atg proteins are known to be involved in autophagy, yet the identity and function of lipid molecules involved remain largely unknown. We investigated the involvement of sphingolipids in autophagy using Saccharomyces cerevisiae. Inhibiting synthesis of the simplest complex sphingolipid, inositol phosphorylceramide (IPC), resulted in reduced autophagic activities. Similar results were obtained using myriocin, an inhibitor of the first step in sphingolipid synthesis. Our results indicate that sphingolipids, especially IPC, are required for autophagy. Inhibition of sphingolipid synthesis had no effect on formation of Atg12-Atg5 or Atg8-phosphatidylethanolamine conjugates, on maturation of vacuolar proteases, or on formation of the pre-autophagosomal structure (PAS). These results suggest that sphingolipids are not involved in the cellular signaling that leads to formation of the PAS, but may be involved in the process of autophagosome formation.  相似文献   

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