首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Thiamine at a concentration of 1×10–14 to 1×10–4 M facilitated neuromuscular transmission at the glutaminergic synapse of the crayfish adapter, manifesting as increased amplitude and quantal content of excitatory postsynaptic potentials and raised frequency of miniature excitatory postsynaptic potentials. Thiamine augmented spontaneous electrical activity and the amplitude of synaptic potentials in the longitudinal muscle of guinea pig taenia coli. It was found from studying the effects of thiamine on the membrane potential of rat brain synaptosomes that its presynaptic action is brought about by depolarization of the nerve terminal membrane. Interaction between thiamine and the nerve endings was described by a Hill coefficient of 0.22–0.30, indicating that it has several binding sites within the structure of the receptor concerned.A. V. Palladin Institute of Biochemistry, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 5, pp. 621–629, September–October, 1986.  相似文献   

2.
A technique is proposed for quantifying the effects of physiologically active substances at the periphery of the auditory analyzer. It was found that applying 1×10–11 to 1×10–3 M thiamine to the membrane of guinea pig cochlear round window (fenestra rotunda) produces a rise in the amplitude and a reduction in the latency of the N1 and N2 components of auditory nerve action potentials, waves I and II of brainstem auditory evoked potentials occurring in response to an acoustic stimulus. It is suggested that this effect is produced by facilitated synaptic transmission at synapses between hair cells and spiral ganglia neurons under the action of thiamine penetrating into the cochlea.A. V. Palladin Institute of Biochemistry, Academy of Sciences of the Ukrainian SSR, Kiev. A. I. Kolomiichenko Research Institute of Otolaryngology, Ministry of Public Health of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 5, pp. 654–660, September–October, 1986.  相似文献   

3.
The effect of vitamin B1 (thiamine, 10–10–10–3 M) on direct (transmitter secretion) and recurrent (resynthesis of the transmitter and its storage in synaptic vesicles) processes of acetylcholine (ACh) secretion was studied in the frog neuromuscular junction. In Ca2+-containing extracellular medium, the facilitatory effects of thiamine and -latrotoxin (an increase in the frequency of miniature end-plate potentials, MEPP) were additive, regardless of the sequence of their application. After partial exhaustion of the synaptic vesicle stores caused by -latrotoxin (2 nM) in Ca2+-free extracellular medium, thiamine accelerated the Ca2+-induced recovery of the ACh secretion. In the presence of thiamine, there were two phases in the dependence of quantum content of an end-plate potential (EPP) on stimulation frequency, which are typical of the effects of Sr2+ and Ba2+ on the ACh secretion. Under conditions of depression and postdepression recovery, the effect of thiamine on the time course of the changes in EPP amplitude was similar to that produced by Ba2+. Possible mechanisms of the effects of vitamin B1 on the processes responsible for the ACh secretion and the dependence of the MEPP frequency on the concentrations of thiamine and thiamine diphosphate are discussed in light of the above results.Neirofiziologiya/Neurophysiology, Vol. 26, No. 4, pp. 291–298, July–August, 1994.  相似文献   

4.
The insoluble fraction of ox-brain, which had previously been shown to have a non-linear affinity for Na+ and K+, was prepared. Acetylcholine (1×10–8 mol/l and 1×10–7 mol/l) reduced the affinity of the fraction for Na+ and K+ to zero, while at 1×10–6 mol/l, the affinity for the cations was almost as high as in the absence of the transmitter; the affinities for Na+ and K+ were particularly high, when the supernatant concentrations of these ions exceeded 80–100 mM. Addition of eserine (3×10–5 mol/l) considerably modified the response of the fraction to acetylcholine (1×10–5 mol/l). Atropine (1×10–8 mol/l) in the absence or presence of acetylcholine (1×10–5, or 1×10–4 mol/l) reduced the affinity of the fraction for Na+ and K+ to zero. Epinephrine (3×10–10 mol/l) lowered the affinity for Na+ and K+, while ergotamine itself (1×10–5 mol/l) reduced it to zero. The addition of both epinephrine and ergotamine at the latter concentrations restored the affinity of the fractions for Na+ and K+ to what it had been in the absence of the transmitter or antagonist, previously reported. Norepinephrine (3×10–10 mol/l), or ouabain (1×10–7 mol/l) reduced the affinity of the fraction for Na+ and K+ to zero. Thus, the transmitters and antagonists altered the affinity of the insoluble fraction for Na+ and K+ nonlinearity, dependent upon their concentrations, the concentrations of the cations, and the interaction of transmitter and antagonist.  相似文献   

5.
Three 5 l working volume fermenters were used to investigate the growth of the yeast Kluyveromyces fragilis in acid cheese whey under ambient temperature in order to assess the specific growth rate and yield, the lactose and oxygen uptake rates during the various phases of batch culture, the effect of increasing temperature on the various kinetic parameters, and the need for a cooling unit for single cell production batch systems. The initial dissolved oxygen in the medium was 5.5 mg l–1 and the pH was maintained at 4.5. The observed lag phase, specific growth rate and maximum cell number were 4 h, 0.2 h–1 and 8.4 × 108 cells ml–1, respectively. About 99% of the lactose in cheese whey was utilized within 20 h, 85% during the exponential growth phase. The specific lactose utilization rates by K. fragilis were 0.20 × 10–12, 1.457 × 10–12, 0.286 × 10–12 and 0.00 g lactose cell–1 h–1, for the lag, exponential, stationary and death phases, respectively. The dissolved oxygen concentration in the medium decreased as the cell number increased. The lowest oxygen concentration of 1.2 mg l–1 was observed during the stationary phase. The volumetric oxygen transfer coefficient was 0.41 h–1 and the specific oxygen uptake rates were 0.32 × 10–12, 2.14 × 10–12, 0.51 × 10–12 and 0.003 × 10–12 mg O2 cell–1 h–1, for the lag, exponential, stationary and death phases, respectively. The maximum temperature recorded for the medium was 33 °C, indicating that a cooling unit for batch production of single cell protein at ambient temperature is not needed for this type of bioreactor. The increase in medium temperature affected the cell growth and the lactose and oxygen uptake rates.  相似文献   

6.
The characteristics of water diffusional permeability (P) of human red blood cells were studied on isolated erythrocytes by a doping nuclear magnetic resonance technique. In order to estimate the basal permeability the maximal inhibition of water diffusion was induced by exposure of red blood cells to p-chloromercuribenzene sulfonate (PCMBS) under various conditions (concentration, duration, temperature). The lowest values of P were around 0.7×10–3 cm s–1 at 10°C, 1.2×10–3 cm s–1 at 15°C, 1.4×10–3 cm s–1 at 20°C, 1.8×10–3 cm s–1 at 25°C, 2.1×10–3 cm s–1 at 30°C and 3.5×10–3 cm s–1 at 37°C. The mean value of the activation energy of water diffusion (Ea,d) was 25 kJ/mol for control and 43.7 kJ/mol for PCMBS-inhibited erythrocytes. The values of P and Ea,d obtained after induction of maximal inhibition of water diffusion by PCMBS can be taken as references for the basal permeability to water of the human red blood cell membrane.  相似文献   

7.
This study describes the synthesis, receptor binding characteristics, and some behavioral effects of p-bromoacetamidoprocaine (BAP), a new affinity ligand for brain muscarinic and nicotinic cholinergic receptors. The reversible binding of [3H]QNB to rat brain membranes was inhibited in a concentration dependent and saturable manner by both procaine and BAP, with Ki values of 4×10–6 and 3×10–7 M, respectively, and complete inhibition at 1×10–5 M. Both procaine and BAP, although at much concentrations, inhibited the binding of [3H]methylcarbamylcholine in a concentration dependent manner, with Ki values of 5×10–5 and 1×10–5 M, respectively, and complete inhibition for both at 1×10–3 M. Plots of the % irreversible inhibition of [3H]QNB, [3H]nicotine, and [3H]MCC vs [BAP] yielded Ki values of 7×10–8, 1×10–4, and 6×10–5 M, respectively. In behavioral studies BAP was able to antagonize the QNB-induced hyperactivity in mice; however, BAP did not appear to alter nicotine-induced seizure activity or other behavioral effects in mice. A plot of the time course of inhibition by BAP for [3H]QNB binding revealed that the inhibition was almost complete within 10 min exposure at 37°. The findings indicate that BAP is a useful affinity ligand for examining the biochemical and functional characteristics of brain cholinergic receptors, particularly the muscarinic which has an affinity near the nM concentration range.  相似文献   

8.
The tolerance of sol-gel immobilised and free Saccharomyces cerevisiae to ethanol was studied. The effects of ethanol preincubation time showed that the specific death velocity decreased from 2×105 c.f.u. min–1 for free cells to 2×104 c.f.u. min–1 for immobilised cells thus indicating that immobilised yeast was far less sensitive to the ethanol damage. The specific glucose consumption of immobilised and free cells on a per cell basis was 3×10–12 g cell–1 h–1 and 9×10–12 g cell–1 h–1, respectively.  相似文献   

9.
In situ uptake of inorganic carbon and nitrogen by the aquatic liverworts Jungermannia vulcanicola Steph. and Scapania undulata (L.) Dum. was measured in an acid stream, Kashiranashigawa, Japan. The uptake activities were similar in the both species. The activities were highest at the tip of shoots, and decreased gradually towards the base. Carbon uptake at the tip in the light was 10.4 × 10–4 for J. vulcanicola and 8.1 × 10–4 g C g dry wt–1 h–1 1 for S. undulata. Ammonium was effectively incorporated into the shoots, and the uptake activity at the tip was between 1.9 × 10–5 and 5.8 × 10–5 g N g dry wt–1 h–1. Nitrate uptake was smaller than ammonium uptake. The ratio of dark to light uptake in ammonium uptake experiments was larger than that in carbon uptake experiments. These results suggest that the liverworts use ammonium as a major nitrogen source, and that ammonium uptake was less dependent on light than carbon uptake.  相似文献   

10.
Insulin binding in adipocytes from patients with a phaeochromocytoma (PH) approached that of the controls (C) at low and higher concentrations of unlabeled insulin. The apparent receptor affinity was unchanged (ED50: PH 0.50×10–9M and C0.60×10–9M). Scatchard analysis of the binding data using the negative cooperative model revealed a 46% decrease in the total number of receptors together with no changes in both Ke (PH 0.55×109M–1 and C 0.36×109M–1) and Kf (PH 0.13×109 M–1 and C 0.07×109 M–1). According to the two site model, an altered proportion in the two classes of insulin binding sites was detected. This was accompanied by a catecholamine-desensitization of the adipocytes to the antilipolytic action of insulin. These events could represent a final situation of a chronic and endogeneous regulation by high levels of catecholamines of insulin receptors in human adipose tissue.  相似文献   

11.
Summary Na+ and sugar permeabilities of egg lecithin bilayers were measured using curved bilayers and planar bilayers as represented by single-bilayer vesicles and black lipid films, respectively. The Na+ permeability coefficient measured with single-bilayer vesicles at 25°C is (2.1±0.6)×10–13 cm sec–1. Because of technical difficulties it has been impossible to measure ionic permeabilities of values lower than about 10–10 cm sec–1 in planar (black) lipid bilayers using tracer methods. Thed-glucose andd-fructose permeabilities were measured with both curved and planar bilayers. The permeability coefficients measured with vesicles at 25°C are (0.3±0.2)×10–10 cm sec–1 for glucose and (4±1)×10–10 cm sec–1 ford-fructose; these are in reasonable agreement with the corresponding values obtained for planar (black) lipid bilayers which are (1.1±0.3)×10–10 cm sec–1 ford-glucose and (9.3±0.3)×10–10 cm sec–1 ford-fructose, respectively.This paper is dedicated to the memory of Walther Wilbrandt,cuius nomini nullum par elogium.  相似文献   

12.
The human rotavirus titer was optimal at an infection cell density of about 4–8 × 104 cells cm–2 in monkey kidney cell cultures. The highest viral titers (3.8 × 107 TCID50 ml–1 and 3.7 × 107 TCID50 ml–1) were obtained at an multiplicity of infection of 0.05 in well plate and T-flask, respectively.  相似文献   

13.
Glasshouse experiments were conducted to evaluate the influence of L-TRP in comparison with indole-3-acetamide (IAM), tryptophol (TOL) and indole-3-acetic acid (IAA) on the growth of Zea mays L. var. Early Sunglow. L-TRP (25 to 2.5×10–5 mg kg–1 soil), IAM (22 to 2.2×10–5 mg kg–1 soil), TOL (20 to 2.0×10–5 mg kg–1 soil), and IAA (22 to 2.2×10–5 mg kg–1 soil) were applied as a soil drench to established uniform seedlings. All treatments were applied in a completely randomized design with 10 replicates. IAM had no significant effect on the plant growth parameters. Shoot height, uppermost leaf collar base distance, internodal distance, and shoot dry and fresh weights were significantly improved upon the addition of TOL (2.0×10–2 mg kg–1 soil), however, the highest concentration (20 mg kg–1 soil) caused a 14.6% reduction in leaf width. L-TRP (2.5×10–3 mg kg-1 soil) also had a significant influence on shoot height, uppermost leaf collar base distance, internodal distance and fresh weight of shoot compared with the control. The highest concentration of L-TRP (25=mg kg–1 soil) had a negative effect on leaf width and dry weight of the shoot. The most pronounced response on the corn growth parameters was observed with the application of IAA at lower concentrations (2.2×10–5 to 2.2×10–2 mg kg–1 soil) specifically improving root growth. The highest concentration (22 mg kg–1 soil) of IAA had a significant negative effect on plant height, leaf width, stem diameter, shoot fresh and dry weight. These findings indicate that L-TRP applied at the appropriate concentrations can have positive effects on corn growth comparable to pure auxins (TOL and IAA).  相似文献   

14.
Methanogenic activity in thermophilic, anaerobic reactors was determined by comparing the amount of methane generated in single- and two-stage systems with the size of the methanogenic population, as determined by microscopy. The methanogenic activities were 2.71 × 10–9 ml methane cell–1 d–1 and 1.10 × 10–9 ml methane cell–1 d–1 for 10 and 4 days of the hydraulic retention time (HRT), in the single-stage system. In the two-stage system, 7.49 × 10–9 ml methane cell–1 d–1 in the acidogenic reactor and 1.56 × 10–9 ml methane cell–1 d–1 in the methanogenic reactor for 4 days of the HRT. A high correlation was evident between the methane production and methanogenic population [0.1354 ln(x) – 2.1375](R 2 0.8619).  相似文献   

15.
It was found during experiments on isolated frog spinal cord involving extracellular recording from the dorsal roots (sucrose bridging) and intracellular recording from motoneurons by microelectrodes that 10 mM of the M-cholinomimetic arecoline produces motoneuronal depolarization which is matched by depolarizing electronic ventral root potentials and a rise in motoneuronal input resistance. Arecoline changes synaptic transmission by increasing the amplitude of postsynaptic potentials during intracellular recording and that of motoneuronal reflex discharges in the ventral roots but reduces the duration of dorsal root potentials. In the presence of arecoline, L-glutamate-induced motoneuronal response increases. Facilitation of synaptic transmission produced by arecoline in the spinal cord is bound up with cholinergic M2- activation, since it is suppressed by atropine but not by low concentrations of pirenzipine; it is also coupled with a reduction in adenylcyclase activity. When motoneuronal postsynaptic response has been suppressed, as in the case of surplus calcium or theophylline, arecoline produces an inhibitory effect on the amplitude of motoneuronal monosynaptic reflex discharges which is suppressed by pirenzipine at a concentration of 1×10–7 M. This would indicate the presence at the primary afferent terminals of presynaptic cholinergic M1 receptors which mediate its inhibition of impulses of transmitter release. This effect is independent of changes in cyclic nucleotide concentration.A. M. Gorkii Medical Institute, Donetsk. Translated from Neirofiziologiya, Vol. 19, No. 3, pp. 399–405, May–June, 1987.  相似文献   

16.
Summary The pH and serum dependence of the glutamine decomposition rate constant, Kgln, in Dulbecco's Modified Eagle's Medium, DMEM, was determined. The findings indicate that Kgln increases with increase in pH and fetal calf serum (FCS) concentration in DMEM. At a constant pH of 7.25, Kgln increases from 5.7×10–4 to 13.2×10–4 h–1 as FCS content of the medium increases from 0.0 to 10.0 (% v/v). Moreover, at a constant FCS of 10 (% v/v), Kgln increases from 11.5×10–4 to 33.6×10–4 h–1 as pH of the medium increases from 7.2 to 7.6.  相似文献   

17.
Reassessement of bioenergetic growth yield of Arthrospira platensis was performed by using continuous culture under both autotrophic and mixotrophic conditions. Continuous culture was carried out at dilution rates of 0.017, 0.023 and 0.030 h–1. Under these dilution rates bioenergetic yields ranged between 4.45–6.03 × 10–3 g biomass kJ–1 and between 5.42–7.46 × 10–3 g biomass kJ–1, under autotrophic and mixotrophic conditions respectively. A maximum bioenergetic yield of 8.1 × 10–3 g biomass kJ–1 using an autotrophic culture can be calculated. Pigment accumulation (chlorophyll a and carotenoids) may be related to light irradiance, reaching a maximum pigment concentration under light saturation irradiance. Phycocyanin concentration increased during light limitation.  相似文献   

18.
Food concentration (0.5 × 103 – 5 × 105 Scenedesmus cells m1–1) significant influenced the somatic growth, maturation and survivorship ofS. proboscideus larvae. A density of 5 × 104 cells m1–1 was optimal for early larval stages. Of four temperature tested (20–35 °C), 30 °C resulted in the best growth and survival. Maturation time was inversely related to temperature, and was size- rather that age-dependent. Larvae were tolerant of a wide conductivity range, but optimal growth and survival were observed at 260 µS cm–1. Nitrate-Nitrogen (NO2-N) caused a larval mortality of 50% after 24 h at 0.58 mg1–1.  相似文献   

19.
Summary Catharanthus roseus cells (C87N) grown in a 30 litre airlift vessel achieved a growth rate of 0.366 day–1. The maximum biomass yield (9.13 gl–1) was recorded after 168 hours (7 days). On-line analysis of the composition of inlet and outlet gas streams during the growth cycle allowed calculation of the metabolic activity of the cultures. Oxygen uptake on a dry weight basis reached a maximum of 4.5×10–4 Moles O2 g dry weight–1 h–1 after 96 hours (during the mid-logarithmic phase of growth) and a maximum of 2.7×10–3 Moles O2 l–1 h–1 on a volume basis (towards the end of the logarithmic phase). Carbon dioxide production ran in parallel with oxygen use with maxima at 4.2×10–4 Moles CO2 g dry weight–1 h–1 and 3.4×10–3 Moles g l–1 h–1 respectively.  相似文献   

20.
In research on -aminobutyric acid (GABA) used at different concentrations on the amplitude of EPSP within populations (PEPSP), as recorded from dentrites in isolated hippocampal slices, GABA induced a dose-dependent reversible reduction in PEPSP amplitude with no noticeable signs of desensitization. Highest sensitivity to GABA was shown by PEPSP in hippocampal zone CA1 (threshold concentration: 3×10–5–2×10–4 M; (concentration at which the effect equal to 1/2 of maximum occurs) IC50: 5×10–4–1×10–3 M). The effects of GABA on PEPSP were not blocked by bicuculline, picrotoxin, or penicillin. Action of GABA on dendritic antidromic population spike (DAPS — postynaptic effects) were slightly diminished by these blockers. Baclofen inhibited PEPSP more powerfully than GABA (threshold concentration: 1×10–6 M: IC50: 3×10–6 M), although it only produced a minor reduction in DAPS amplitude even at high concentrations. It is concluded that the inhibitory effect of GABA on PEPSP in hippocampal zone CA1 may be put down mainly to its presynaptic action mediated by GABAB receptors on axonal terminals of Schaffer collaterals.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 5, pp. 627–633, September–October, 1990.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号