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941.
Statistical inference from single channel records: two-state Markov model with limited time resolution 总被引:4,自引:0,他引:4
G F Yeo R K Milne R O Edeson B W Madsen 《Proceedings of the Royal Society of London. Series B, Containing papers of a Biological character. Royal Society (Great Britain)》1988,235(1278):63-94
Though stochastic models are widely used to describe single ion channel behaviour, statistical inference based on them has received little consideration. This paper describes techniques of statistical inference, in particular likelihood methods, suitable for Markov models incorporating limited time resolution by means of a discrete detection limit. To simplify the analysis, attention is restricted to two-state models, although the methods have more general applicability. Non-uniqueness of the mean open-time and mean closed-time estimators obtained by moment methods based on single exponential approximations to the apparent open-time and apparent closed-time distributions has been reported. The present study clarifies and extends this previous work by proving that, for such approximations, the likelihood equations as well as the moment equations (usually) have multiple solutions. Such non-uniqueness corresponds to non-identifiability of the statistical model for the apparent quantities. By contrast, higher-order approximations yield theoretically identifiable models. Likelihood-based estimation procedures are developed for both single exponential and bi-exponential approximations. The methods and results are illustrated by numerical examples based on literature and simulated data, with consideration given to empirical distributions and model control, likelihood plots, and point estimation and confidence regions. 相似文献
942.
The ionic mechanisms of hyperpolarization produced by applying oxytocin (OT) were investigated at the membrane of identifiedHelix
pomatia neurons. Two types of neuron were known to exist, in one of which hyperpolarization is produced by a reduction in chloride ions at the membrane and a rise in membrane permeability to potassium ions in the other. In the first of these, response to OT had a reversal potential of –40 mV and decreased when furosemide and tolbutamide were added to the external medium. In the second case, the potential of the reversal of the response to OT was –70 mV. Upon doubling of potassium ion concentration in the external solution it was shifted towards depolarization by 15 mV. It is sugested thatHelix
pomatia neurons have different types of OT receptors, some of which, when activated, manifest reduced chloride permeability at the membrane (probably through the cell cyclase system) with a rise in potassium permeability at the membrane in others.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 20, No. 5, pp. 659–666, September–October, 1988. 相似文献
943.
The occurrence of tularemia was studied in 1,500 hares submitted to the National Veterinary Institute, Uppsala, Sweden for postmortem examination during 1973 through 1985. A total of 109 tularemia cases was recorded based on the fluorescent antibody (FA) test for Francisella tularensis and on the gross and microscopic pathology. Tularemia was diagnosed only in the varying hare (Lepus timidus) and not in the European brown hare (Lepus europaeus). The geographical distribution of the 109 cases indicates that tularemia has not spread in Sweden during the last 45 yr, with the exception of an endemic occurrence of the disease on the island of Stora Karls? in the Baltic sea. The disease was most frequent in the autumn and only a few cases were recorded during winter. Cases were not seen in the spring. The annual prevalence varied, with several cases in 1974 and 1981, but there were no cases in 1976 and 1980. The postmortem findings in hares dying of tularemia in the autumn were characterized by focal coagulative necrosis in liver, spleen and bone marrow, with high numbers of bacteria FA-positive for F. tularensis. In hares dying during winter months, the most characteristic findings were hemorrhagic enteritis and typhlitis, although necrotic lesions could occur in liver, spleen and bone marrow. Diseased hares on the island of Stora Karls? were demonstrated to be infected with ticks, while hares on the mainland of Sweden generally were fed upon by mosquitoes. Twenty-six of the 109 hares with tularemia were examined bacteriologically and F. tularensis biovar palaearctica was isolated from eight. The lung extract antibody test for F. tularensis was performed in 18 of the 109 hares. All were negative. In addition to the field study, an experimental study with F. tularensis biovar palaearctica was performed. Four varying hares and three European brown hares were inoculated. None of the hares died from tularemia, and generalized infection was not demonstrated. 相似文献
944.
V S Rusinov O M Grindel' E V Sharova M A Kulikov V N Kaliuzhny? 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1988,38(2):207-218
The data are given of the analysis of the low-frequency EEG component (LF EEG--0.2--2.0 Hz) of 34 healthy subjects and 36 patients examined in dynamics in the acute period after operations: ablation of a tumour localized at the level of the diencephalon and the level of the brainstem. The LF EEGs were analyzed by a special program: auto- and crosscorrelation functions and power spectra were estimated. In the norm LF EEGs were characterized by mosaics, various frequencies and periodicity in various cortical areas, they appeared with interhemispheric asymmetry, depended on the EEG type--dominance or lack of the alpha-rhythm. In patients in the post-operative period the LF EEGs were changed; in favourable terminations, at first the period of oscillations and the coefficient of correlation increased, then they tended to normalization. In unfavourable terminations, with gross pathological foci in these areas, the LF EEGs acquired a synchronized character, with a higher frequency than in the norm. 相似文献
945.
T A Petrova O V Shamova S N Lyzlova 《Zhurnal evoliutsionno? biokhimii i fiziologii》1988,24(4):489-496
Electrophoretic studies have been made of the protein composition and isozymic pattern of the creatine kinase from muscles of the cod. It was shown that this enzyme constitutes up to 40% of total water-soluble proteins of muscle tissue. Isolation and purification procedures were suggested for the creatine kinase from cod muscles which allow to obtain the enzyme with the specific activity 250-350 IU/mg. Comparative enzymic analysis of creatine kinases from muscle tissue of the cod, lake frog, and rabbit was also made. Studies were carried out on temperature dependence of the reaction, kinetic constants at temperatures 5 and 30 degrees C were determined together with other physicochemical properties of the enzymes. The revealed species specific differences are discussed in relation to the structure and function of the enzymes in lower vertebrates in vivo. 相似文献
946.
In experiments on Wistar line young rats immunized in the early postnatal period with antigenic complexes of the nervous tissue of the hippocampus or the neocortex of an adult rat, the influence was studied of the change of the immunoreactivity to antigenic complexes of these structures on the functional brain development. Experimental animals were immunized twice in the age of 5 and 12 days or daily in the first 7 days of life. Studies of the behaviour of experimental and control animals in various situations, beginning from the two-weeks age, revealed expressed distinctions in the behaviour of animals, immunized by the hippocampus antigens: reduction of the capability to change the behaviour in changed experimental conditions (two-weeks age), and also a deficit of orienting (three weeks age) and conditioned (six weeks age) activities. A raised level was found of anticerebral antibodies in 1.5-months animals immunized in the early age. Suggestion is expressed about the significance of neuroimmune interaction in the mechanisms of the functional brain development. 相似文献
947.
Cytochemical and ultrastructural features of mouse hybridomas and also of the parental cells--myeloma P3-X63-Ag8.653 and spleen cells of the Balb/c mice immunized with cell line RPMI-1788 have been studied. Differences in cytomorphological signs and activity of acid phosphatase, acid nonspecific esterase, nonspecific-alpha-naphthyl acetate esterase were shown in hybrid cell lines secreting and not secreting monoclonal antibodies. 相似文献
948.
949.
950.
Site-specific endonucleolytic cleavages and the regulation of stability of E. coli ompA mRNA 总被引:53,自引:0,他引:53
The stability of ompA mRNA is growth-rate dependent. We show that the 5' noncoding region of this mRNA provides a target for site-specific endonucleases. The rate of degradation of ompA mRNA parallels the rate of these endonucleolytic cleavages, implying that endonucleolytic rather than exonucleolytic attack is the initial step in ompA mRNA degradation. Thus the 5' noncoding region appears to be a determinant of mRNA stability, and endonucleolytic cleavages in the 5' noncoding region may well regulate expression of the ompA gene. 相似文献