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51.
Changes in the position of the minimum of the parabolic capacitance-voltage curve allow the measurement of the amount of ganglioside present in artificial bilayers made with phosphatidylcholine-ganglioside mixtures and asymmetrically shielded with Ca2+. The screening effect of the ionic solution must be considered. With ganglioside/phospholipid molar ratios of up to 15%, all glycolipids can be found at the membrane surfaces. 相似文献
52.
Suren A. Tatulian 《生物化学与生物物理学报:生物膜》1983,736(2):189-195
Temperature dependence of the electrophoretic mobility of multilamellar liposomes prepared from dimyristoylphosphatidylcholine was measured in the presence of salts with different anions in aqueous solutions. It was established that specific binding of anions to liposome surface induced a pronounced zeta potential (electrostatic potential at the hydrodynamic plane of shear). A combination of Langmuir, Gouy-Chapman, and Boltzmann equations was used to describe the dependence of the zeta potential on the concentration of anions. The values of binding constants (K) and maximum numbers of binding sites per unit area (σmax) were determined by this method. The sequence for anion affinities to liposome surface was found to be as follows: trinitrophenol >ClO4− >I− >SCN− >Br− >NO3− >Cl− SO42−. A sharp increase in the negative zeta potential was detected at the temperature of phase transition of the lipid from the gel to liquid-crystalline state. It was found that the parameter K did not change at lipid phase transition and the shifts in zeta potential might be due to alterations of σmax. The binding sites were considered as defects in the package of lipid molecules in membranes. 相似文献
53.
Summary The amount of vesicular-arbuscular mycorrhizal (VAM) infection, when expressed as length of infected roots, is commonly quite variable among replicate pots within an experimental treatment. In this paper we show that frequency distributions of VAM infection parameters are often non-normal in form and may follow the negative binomial, a distribution commonly associated with aggregated organisms in nature. The lack of normality means that statistical procedures should either be non-parametric or should include data transformations. 相似文献
54.
Z. Krupa 《Photosynthesis research》1983,4(3):229-239
Thylakoid membranes obtained from bean chloroplasts treated with bean galactolipase or phospholipase A2 (from Crotalus terr. terr.) showed marked changes in their polypeptide patterns when separated on SDS-PAGE. The obtained results have been discussed with regard to the relationship between chloroplast lipids and polypeptides originating from chlorophyll-protein complexes of bean thylakoids. A coexistence between galactolipids and the peripheral antennae in PS I complex and LHCP3 as well as a conspicuous role of phospholipids in PSI and PSII centre chlorophyll-protein complexes has to be underlined.Abbreviations CP1
chlorophyll a-protein complex of PSI
- CPa
chlorophyll a-protein complex of PSII
- D10
digitonin subchloroplast particles enriched in PSII
- D144
digitonin subchloroplast particles enriched in PSI
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- LHCP1–3
light harvesting chlorophyll a/b protein complexes
- PAGE
polyacrylamide gel electrophoresis
- PSI
photosystem I
- PSII
photosystem II
- SDS
sodium dodecyl sulphate
- TCA
trichloroacetic acid
- Tricine
N-Tris-(hydroxymethyl)-methylglycine
- Tris
Tris-(hydroxymethyl)-aminomethan 相似文献
55.
This study examined the efficacy of muscle relaxation training via electromyographic (EMG) biofeedback from the frontalis and forearm extensor muscles of schizophrenic inpatients. Thirty chronically hospitalized patients were randomly assigned to one of three conditions: EMG biofeedback from the forearm extensor and frontalis muscles, progressive relaxation, and a control group. Treatment consisted of one session of orientation and baseline, and six sessions of training. The results indicated that the schizophrenic patients receiving EMG training had significantly lower EMG recordings than the progressive relaxation group, which, in turn, was significantly lower than the control group. Analyses of covariance on the Tension-Anxiety scale from the Profile of Mood States revealed no significant effects, while finger-tapping rates were significantly improved only for the arm receiving feedback training in the EMG group. On the Nurses Observation Scale for Inpatient Evaluation the biofeedback group significantly improved on the Social Competence and Social Interest factors.We would like to express our appreciation for the contributions the following people made to this project: Drs. Barry Smith, Robert Steele, Agnes Hartfield, Jeffrey Barth, Althea Wagman, and the late Harold Weiner; Earl Downs and the participating staff at Springfield State Hospital Center; and Robert Kline and Michael Kelley, who performed the data analyses. This research was supported in part by a grant from the Computer Science Center at the University of Maryland. 相似文献
56.
M. G. Corda O. Giorgi B. Longoni M. Orlandi G. Biggio 《Journal of neurochemistry》1990,55(4):1216-1221
The acute administration of pentylenetetrazol (PTZ; 25-75 mg/kg i.p.) failed to modify the specific binding of t-[35S]butylbicyclophosphorothionate ([35S]TBPS) to membrane preparations from the cerebral cortex of the rat. In contrast, the repeated administration of PTZ (30 mg/kg i.p., three times a week for 12 weeks) reduced by 26% the density of [35S]TBPS binding sites without modifying the dissociation constant. This effect was observed 3 days after the last PTZ administration. A parallel reduction of gamma-aminobutyric acid (GABA)-stimulated 36Cl- uptake was measured in the cerebral cortex of PTZ-treated rats 3 days after the last injection. The repeated administration of PTZ produced sensitization to the drug, or chemical kindling. In fact, no convulsions were observed in the first week of treatment, but all the animals became sensitized to PTZ by the 12th week. The results are consistent with the hypothesis that chronic treatment with PTZ at a subconvulsant dose causes a decrease in GABA-coupled chloride channel activity that may be related to the chemical kindling produced by this compound. 相似文献
57.
Heat treatment of ripening apples: Differential effects on physiology and biochemistry 总被引:22,自引:0,他引:22
Apples ( Malus domestica Borkh.) were heated for 4 days at 38°C immediately after harvest and then placed at 20°C for 7–10 days. Protein synthesis, ethylene production and fruit softening were reversibly inhibited by the heat treatment. Fruit respiration, membrane permeability and chlorophyll degradation in the fruit peel were enhanced during the treatment. The heat-treated apples ripened normally but more slowly than untreated apple We hypothesize that heat treatment differentially affects processes which normally increase simultaneously during fruit ripening, by inhibiting those processes which require tie novo protein synthesis and enhancing those that do not. 相似文献
58.
本文报道小剂量干扰素与胸腺肽联合对慢性乙肝20例抗病毒效应的追踪观察结果,并与同期同批同剂量单纯干扰素治疗13例慢性乙肝作对照,追踪时间均为治后半年—2年,从HBeAg、HBcAg、DNAP、HBV DNA阴转率来看,治疗组分别为58.8%、60%、60%及66.6%、对照组分别为50%、50%、100%及50%。再从HBV四项复制指标改变来看,则治疗组4例全阴转,7例仅一项阳性,总有效率达61.1%(11/18),而对照组仅为20%(2/10),P<0.01,认为干扰素与胸腺肽联合治疗优于对照组,并扼要讨论增强干扰素抗病毒效应的各种措施,认为干扰素与胸腺肽联合,不论从前已报道近期疗效和本文远期追踪来看均较安全而有效,二者合用起到增强抗病毒效应的作用,值得进一步探索。 相似文献
59.
Hyperpolarization-activated K channels (K
H
channels) in the plasmalemma of guard cells operate at apoplastic pH range of 5 to over 7. Using patch clamp in a whole-cell
mode, we characterized the effect of varying the external pH between 4.4–8.1 on the activity of the K
H
channels in isolated guard cell protoplasts from Vicia faba leaves.
Acidification from pH 5.5 to 4.4 increased the macroscopic conductance of the K
H
channels by 30–150% while alkalinization from pH 5.5 to 8.1 decreased it only by roughly 15%. The voltage-independent maximum cell conductance, increased by ∼60% between pH 8.1 and 4.4 with an apparent pK
a
of 5.3, most likely owing to the increased availability of channels. Voltage-dependent gating was affected only between pH 5.5 and 4.4. Acidification in this range shifted the voltage-dependent open probability by over 10 mV. We interpret this shift as an increase of the electrical field sensed by the gating subunits
caused by the protonation of external negative surface charges. Within the framework of a surface charge model the mean spacing
of these charges was ∼30 ? and their apparent dissociation constant was 10−4.6. The overall voltage sensitivity of gating was not altered by pH changes. In a subgroup of protoplasts analyzed within the
framework of a Closed-Closed-Open model, the effect of protons on gating was limited to shifting of the voltage-dependence
of all four transition rate constants.
Received: 26 April 1996/Revised: 29 June 1996 相似文献
60.
山茶科紫茎属和舟柄茶属的系统学研究 总被引:6,自引:0,他引:6
本文对山茶科紫茎属和舟柄茶属进行了深入细致的系统学研究,藉助形态学、古植物学、孢粉学,细胞学和解剖学资料澄清了两属的分合问题,证实两属在各方面具有较大相似性,并且各分类特征存在广泛的联系而无法分开,从而赞同H.K.Airy Shaw,J.R.Sealy及S.A.Spongberg的主张,即将这两属合并。在此基础上本文提出了世界范围广义紫茎属下分类系统。属下新系统根据花柱合生程度、花序类型,苞片与萼片的形状以及两者的相对长度等特征,分为两个亚属,五个组,同时对该属种类进行修订。该属共有23种5变种,本文发表新组1个,新名称2个,新组合9个,新异名10个,新种1个,并附有分种检索表。广义的紫茎属为东亚-北美间断分布类型,中国南部和西南部是该属的起源中心和高度分化中心。根据化石资料推断,该属起源于早白垩纪,在第三纪以前于整个劳亚古陆上呈广泛而连续的分布,后因冰川及造山运动的影响,从而形成现在的分布格局。 相似文献