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101.
Alexander V Lukashin 《Current opinion in neurobiology》1996,6(6):765-772
A current challenge in computational neuroscience is to elucidate the role of cortical circuitry in information processing and in generating motor output. Our understanding of the functional significance of specifically organized feedback connections is progressing rapidly as researchers establish the equivalence of theoretical models to biological neural circuits. Modeling studies of different neural structures, along with quantitative comparisons of model performance to biological data, have recently helped to identify the basic features of synaptic connectivity that may play important roles in cortical operations. 相似文献
102.
D. A. Alexander A. A. Naji S. B. Pinion J. Mollison H. C. Kitchener D. E. Parkin D. R. Abramovich I. T. Russell 《BMJ (Clinical research ed.)》1996,312(7026):280-284
OBJECTIVE: To compare in psychiatric and psychosocial terms the outcome of hysterectomy and endometrial ablation for the treatment of dysfunctional uterine bleeding. DESIGN: Prospective randomised controlled trial. SETTING--Obstetrics and gynaecology department of a large teaching hospital. SUBJECTS: 204 women with dysfunctional bleeding for whom hysterectomy would have been the preferred treatment were recruited over 24 months and randomly allocated to hysterectomy (99 women) or to hysteroscopic surgery (transcervical resection (52 women) or laser ablation (53 women). MAIN OUTCOME MEASURES: Mental state, martial relationship, psychosocial and sexual adjustment in assessments conducted before the operation and one month, six months, and 12 months later. RESULTS: Both treatments significantly reduced the anxiety and depression present before the operation, and there were no differences in mental health between the groups at 12 months. Hysterectomy did not lead to postoperative psychiatric illness. Sexual interest after the operation did not vary with treatment. Overall, 46 out of 185 (25%) women reported a loss sexual interest and 50 out of 185 (27%) reported increased sexual interest. Marital relationships were unaffected by surgery. Personality and duration of dysfunctional uterine bleeding played no significant part in determining outcome. CONCLUSIONS: Hysteroscopic surgery and hysterectomy have a similar effect on psychiatric and psychosocial outcomes. There is no evidence that hysterectomy leads to postoperative psychiatric illness. 相似文献
103.
Detached leaves of Cyclamen persicum Mill. can be used as a simple source-sink system. Phloem transport in the excised material was monitored by the noninvasive 11C-technique. Assimilate movement stopped immediately when the petiole was cut off. However, within 20 min a recovery of transport was observed. The translocation rate in the detached leaf was only 13% of that in the intact plant. 14C-Xenobiotics and [3H]sucrose were injected into the upper petiole parenchyma (source). They moved downstream by a symplastic route. The stump of the petiole was inserted into a buffer solution containing ethylenediaminetetraacetic acid (sink). After 3 h, the distribution of sucrose and xenobiotics was determined in five subsequent segments of the petiole (path). The retention coefficient (r) was calculated from the ratio of radioactivity in the vascular bundle to that in the petiole parenchyma. The distribution along the vascular path was given by a geometric progression, whereas its constant was the transport coefficient (q). Values of r and q corresponded with the degree of phloem mobility and ambimobility. Four groups of compounds were classified: (i) acidic substances with log Kow = — 2 to — 2.4 (Kow is the partition coefficient octanol/water) at pH 8 (pH of sieve tube sap), retained by ion trapping and exhibiting small lateral efflux (q0.7; maleic hydrazide, dalapon); (ii) acidic substances with log Kow = — 0.7 to — 0.8 at pH 8, retained by ion trapping and subjected to a moderate lateral efflux (0.7>q> 0.5; 2,4-dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid, bromoxynil); (iii) nonionised substances retained by optimum permeability, exhibiting a considerable lateral leakage (q<0.5; glyphosate, amitrole); (iv) substances without basipetal transport in the phloem (atrazine, diuron). Retention of sucrose corresponded quantitatively with that shown in group (i). This classification was also supported by results of uptake and efflux experiments using the isolated conducting tissue. Theoretical translocation profiles were calculated from the determined transport coefficients (q).Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- Kow
partition coefficient octanol/water
- MCPA
2-methyl-4-chloro-phenoxyacetic acid
- q
transport coefficient in the vascular bundle
- r
retention coefficient in the vascular bundle
The authors gratefully acknowledge the assistance of H. Fiedler and M. Neugebauer. We are particularly grateful to K. Dutschka, G. Hudepokl, and Dr. J. Knust for producing 11CO2. 相似文献
104.
The effects of abscisic acid (ABA) treatments on the surfaceelectrical properties of cells and isolated protoplasts fromCatharanthus roseus cell suspension cultures were studied byelectrophoretic mobility and 9-aminoacridine (9AA) fluorescencemeasurements. The surface charge densities of the cells andprotoplasts estimated from electrokinetic data were 0.064Cm2and 0.048 C m2 respectively. These values wereclose to that estimated by 9AA fluorescence technique i.e.,0.053 Cm2 for the cells and 0.041 Cm2for the isolated protoplasts accordingly. The net negative surfacecharge density decreased after application of 10 µM and50 µM ABA in both cells and protoplats, the more pronouncedeffect being observed at 10 µM ABA. When 100 µMABA was supplemented to the cell suspension culture the oppositeeffect was observed. The average charge density increased to0.074 C m2 for the cells, and to 0.055C m2 for protoplasts, as revealed from the 9AA measurements.The results are discussed in terms of specific concentrationdependent ABA-induced alterations of the electrostatic propertiesof cell and protoplast membranes. (Received December 12, 1994; Accepted April 3, 1995) 相似文献
105.
Enhancement of the light-triggered electrical response in plant cells following their de-energization with uncouplers 总被引:1,自引:0,他引:1
Light-triggered membrane potential changes in cells of a liverwort Anthoceros are greatly enhanced by the ionophorous uncouplers nigericin and monesin. Stimulation of the light-triggered electrical response (LTER) by nigericin occurred concomitantly with inhibition of a slow decline in the chlorophyll fluorescence, which suggests that the transmembrane pH gradient in thylakoids is not essential for generation of LTER at the plasma membrane. The extent of monensin-stimulated LTER remained high under a diminished driving force for the ionophore-induced proton-cation exchange across the plasma membrane (elevation of the external Na+ concentration from 1 to 50 m M ), which indicates that energy uncoupling in chloroplasts is more related to the electric response enhancement than the induction of the H+ /K+ (Na+ ) exchange at the plasma membrane. Enhancement of LTER by ionophores occurs in parallel with stimulation of light-triggered pH changes (alkalinization) in the vicinity of the cell surface, which suggests an association of trans-membrane H+ fluxes with LTER. The results are consistent with the hypothesis that illumination produces a temporary inhibition of the plasma membrane H+ pump with a subsequent activation of gated channels and transient rapid depolarization of the cell. 相似文献
106.
Each cryptomonad strain contains only a single spectroscopic type of biliprotein. These biliproteins are isolated as 50000 kDa '2 complexes which carry one bilin on the and three on the subunit. Six different bilins are present on the cryptomonad biliproteins, two of which (phycocyanobilin and phycoerythrobilin) also occur in cyanobacterial and rhodophytan biliproteins, while four are known only in the cryptomonads. The subunit is encoded on the chloroplast genome, whereas the subunits are encoded by a small nuclear multigene family. The subunits of all cryptomonad biliproteins, regardless of spectroscopic type, have highly conserved amino acid sequences, which show > 80% identity with those of rhodophytan phycoerythrin subunits. In contrast, cyanobacteria and red algal chloroplasts each contain several spectroscopically distinct biliproteins organized into macromolecular complexes (phycobilisomes). The data on biliproteins, as well as several other lines of evidence, indicate that the cryptomonad biliprotein antenna system is primitive and antedates that of the cyanobacteria. It is proposed that the gene encoding the cryptomonad biliprotein subunit is the ancestral gene of the gene family encoding cyanobacterial and rhodophytan biliprotein and subunits.Abbreviations Chl
chlorophyll
- CER
chloroplast endoplasmic reticulum
- SSU rRNA
small subunit ribosomal RNA 相似文献
107.
108.
Alexander A. Bachmanov Danielle R. Reed Yuro Ninomiya Masashi Inoue Michael G. Tordoff R. Arlen Price Gary K. Beauchamp 《Mammalian genome》1997,8(8):545-548
Individual variability in sucrose consumption is prominent in humans and other species. To investigate the genetic contribution
to this complex behavior, we conducted behavioral, electrophysiological, and genetic studies, using male progeny of two inbred
mouse strains (C57BL/6ByJ [B6] and 129/J [129]) and their F2 hybrids. Two loci on Chromosome (Chr) 4 were responsible for over 50% of the genetic variability in sucrose intake. These
loci apparently modulated intake by altering peripheral neural responses to sucrose. One locus affected the response threshold,
whereas the other affected the response magnitude. These findings suggest that the majority of difference in sucrose intake
between male B6 and 129 mice is due to polymorphisms of two genes that influence receptor or peripheral nervous system activity.
Received: 27 January 1997 / Accepted: 17 March 1997 相似文献
109.
110.
Expression of connexin43 mRNA in adult rodent brain 总被引:3,自引:0,他引:3
E. Simbürger Alexander Stang Marian Kremer R. Dermietzel 《Histochemistry and cell biology》1997,107(2):127-137