scholarly journals Elevated [Cl-]i, and [Na+]i inhibit Na+, K+, Cl- cotransport by different mechanisms in squid giant axons.

1996 ◽  
Vol 107 (2) ◽  
pp. 261-270 ◽  
Author(s):  
G E Breitwieser ◽  
A A Altamirano ◽  
J M Russell
Keyword(s):  
The Other ◽  
Transport Activity ◽  
Inhibitory Effects ◽  
Giant Axons ◽  
Cl Transport ◽  
Other Hand ◽  
Na Efflux ◽  
Dependent Inhibition ◽  
Unidirectional Fluxes ◽  
Release Model

Bumetanide-sensitive (BS) unidirectional fluxes of (36)Cl- or (22)Na+ were measured in internally dialyzed squid giant axons while varying the intra- or extracellular concentrations of Na+ and/or Cl-. Raising either [Cl-]i or [Na+]i resulted in a concentration-dependent reduction of the BS influx of both (36)Cl- and (22)Na+. Raising [Cl-]i above 200 mM completely blocked BS influxes. However, raising [Na+]i to 290 mM resulted in saturable but incomplete inhibition of both BS Na+ influx and BS Cl- influx. The consequences of varying intracellular Cl- on cotransporter effluxes were complex. At lower [Cl-]i values (below 100 mM) intracellular Cl- activated cotransporter effluxes. Surprisingly, however, raising [Cl-]i levels > 125 mM resulted in a [Cl-]i-dependent inhibition of BS effluxes of both Na+ and Cl-. On the other hand, raising [Na+]i resulted only in the activation of the BS Na+ efflux; intracellular Na+ did not inhibit BS efflux even at 290 mM. The inhibitory effects of intracellular Na+ on cotransporter-mediated influxes, and lack of inhibitory effects on BS effluxes, are consistent with the trans-side inhibition expected for an ordered binding/release model of cotransporter operation. However, the inhibitory effects of intracellular Cl- on both influxes and effluxes are not explained by such a model. These data suggest that Cl may interact with an intracellular site (or sites), which does not mediate Cl transport, but does modulate the transport activity of the Na+, K+, Cl- cotransporter.

Electrical interactions between the giant axons of a polychaete worm (Sabella penicillus L.)

1980 ◽  
Vol 84 (1) ◽  
pp. 119-136
Author(s):  
D. Mellon ◽  
J. E. Treherne ◽  
N. J. Lane ◽  
J. B. Harrison ◽  
C. K. Langley
Keyword(s):  
Safety Factor ◽  
Nerve Cord ◽  
Action Potentials ◽  
Divalent Cations ◽  
Muscular Contraction ◽  
The Body ◽  
The Other ◽  
Intracellular Recordings ◽  
Giant Axons ◽  
Other Hand

Intracellular recordings demonstrated a transfer of impulses between the paired giant axons of Sabella, apparently along narrow axonal processes contained within the paired commissures which link the nerve cords in each segment of the body. This transfer appears not to be achieved by chemical transmission, as has been previously supposed. This is indicated by the spread of depolarizing and hyperpolarizing voltage changes between the giant axons, the lack of effects of changes in the concentrations of external divalent cations on impulse transmission and by the effects of hyperpolarization in reducing the amplitude of the depolarizing potential which precedes the action potentials in the follower axon. The ten-to-one attenuation of electronic potentials between the giant axons argues against the possibility of an exclusively passive spread of potential along the axonal processes which link the axons. Observation of impulse traffic within the nerve cord commissures indicates, on the other hand, that transmission is achieved by conduction of action potentials along the axonal processes which link the giant axons. At least four pairs of intact commissures are necessary for inter-axonal transmission, the overall density of current injected at multiple sites on the follower axon being, it is presumed, sufficient to overcome the reduction in safety factor imposed by the geometry of the system in the region where axonal processes join the giant axons. The segmental transmission between the giant axons ensures effective synchronization of impulse traffic initiated in any region of the body and, thus, co-ordination of muscular contraction, during rapid withdrawal responses of the worm.

Studies on the Effect of Plasminogen Activator on the Interaction between α2-Macroglobulin and Plasmin

1978 ◽  
Vol 40 (02) ◽  
pp. 377-386 ◽  
Author(s):  
Naotika Toki ◽  
Sumiyoshi Takasugi ◽  
Hiroyuki Sumi ◽  
Takuso Yamura
Keyword(s):  
Complex Formation ◽  
Plasminogen Activator ◽  
Molecular Form ◽  
The Other ◽  
Free Form ◽  
Inhibitory Effects ◽  
Other Hand ◽  
Α2 Macroglobulin ◽  
Human Plasminogen ◽  
The Difference

SummarySix different plasmins were prepared by incubating human plasminogen with various amounts of streptokinase or urokinase. It was confirmed that the six different plasmins possessed similar caseinolytic activities, and the inhibitory effects of α 1-antitrypsin on caseinolytic activities of the six different plasmins were all the same. On the other hand, interactions between the six different plasmins and α2-macroglobulin were complicated. Plasmins activated by cleavage of plasminogen were almost immediately or effectively inhibited by α2-macroglobulin. However, plasmin activated by complex formation of plasminogen with streptokinase was not so immediately or effectively inhibited by α2- macroglobulin. It was supposed that the difference between these two results on the interaction between plasmin and α2-macroglobulin might be due to the difference in molecular form of plasmin. In the present study, it was also confirmed that streptokinase or urokinase, in free form in the reaction mixture, interfered with the interaction between plasmin and α2-macroglobulin. The cause for such interference was discussed.

Embryonic Responses to Structurally Related Inhibitors

Development ◽  
1960 ◽  
Vol 8 (4) ◽  
pp. 445-456
Author(s):  
Kathe Liedke ◽  
H. B. Gillespie ◽  
Samuel Graff
Keyword(s):  
Nitro Group ◽  
Rana Pipiens ◽  
The Other ◽  
Amino Group ◽  
Inhibitory Effects ◽  
Tail Bud ◽  
Cytotoxic Effects ◽  
Other Hand

Substituted benzotriazoles (Bt) have been shown to bring about interesting inhibitory effects on Rana pipiens embryos of 2-cell to tail-bud stages (Liedke, Engelman, & Graff, 1954, 1955, 1957a, 1957b). These benzotriazoles did not have selective cytotoxic effects on sensitive embryonic structures as similarly substituted benzimidazoles (Bz) and quinoxalines (Q) invariably did. The latter compounds, Bz and Q, were most active against younger stages, especially those in cleavage. On the other hand, it was found that the susceptibility to the benzotriazoles increased with age of embryo; more differentiated stages were affected most. The type of response was determined by the parent structure, but certain substituents, the nitro group in particular, appeared to enhance the magnitude of the effect. The activating effect of the nitro group was in turn modified to varying degree by an accompanying methoxy, hydroxy, or amino group.

Inhibitory effects of calcium ionophore pretreatment of porcine oocytes on polyspermic fertilization

Zygote ◽  
2006 ◽  
Vol 14 (1) ◽  
pp. 17-22 ◽  
Author(s):  
T. Hayashi ◽  
H. Sato ◽  
H. Iwata ◽  
T. Kuwayama ◽  
Y. Monji
Keyword(s):  
Calcium Ionophore ◽  
Inhibitory Effect ◽  
Calcium Ionophore A23187 ◽  
The Other ◽  
Ionophore A23187 ◽  
Inhibitory Effects ◽  
High Concentration ◽  
Maturation Period ◽  
Low Concentration ◽  
Other Hand

The present study examined the inhibitory effects of various pretreatment concentrations (0–100 μM) of the calcium ionophore A23187 on polyspermic fertilization and then examined the effect of the maturation period and the time between calcium ionophore treatment and fertilization on the inhibitory effect of calcium ionophore on polyspermic fertilization. In experiment 1, a high concentration of calcium ionophore (100 μM) increased the rate of activated oocytes, but the rate of fertilization declined. On the other hand, when oocytes were treated with a low concentration of calcium ionophore (10 μM), monospermic fertilization was significantly increased (10 μM; 31.3%) (p < 0.05). In experiment 2, oocytes were cultured for various times (0, 0.5, 3, 6 h) after calcium ionophore treatment (10 μM) before fertilization. The highest rate of monospermic fertilization was detected in the oocytes cultured for 6 h after calcium ionophore treatment before fertilization. In experiments 3 and 4, we examined the effect of the maturation period (40 h or 44 h) on the rate of fertilization and blastulation of oocytes pretreated with calcium ionophore. The treatment of oocytes with calcium ionophore significantly decreased the rate of polyspermic fertilization regardless of the maturation period (44 h: with calcium ionophore 26.25% vs without 78.8%; 40 h: with calcium ionophore 37.5% vs without 77.5%); however, calcium ionophore treatment increased the rates of monospermic fertilization and blastulation of the oocytes matured for 44 h, but not those matured for 40 h. In conclusion, activation with a low concentration of calcium ionophore (10 μM) and a further 6 h of culture before fertilization improved the rate of monospermic fertilization and blastulation.

scholarly journals Inhibition of Antiassociation Activity of Translation Initiation Factor 3 by Paromomycin

2006 ◽  
Vol 51 (1) ◽  
pp. 175-180 ◽  
Author(s):  
Go Hirokawa ◽  
Hideko Kaji ◽  
Akira Kaji
Keyword(s):  
Translation Initiation ◽  
Translation Initiation Factor ◽  
The Other ◽  
Initiation Factor ◽  
Inhibitory Effects ◽  
Ribosomal Subunits ◽  
Other Hand ◽  
Translation Initiation Factor 3

ABSTRACT The effect of paromomycin on the interaction of ribosomal subunits was studied. Paromomycin inhibited the antiassociation activity of initiation factor 3 (IF3). Furthermore, ribosomal subunits were associated to form 70S ribosomes by paromomycin even in the presence of 1 mM Mg2+. Paromomycin did not inhibit the binding of IF3 to the 30S ribosomal subunits. On the other hand, IF3 bound to the 30S subunits was expelled by paromomycin-induced subunit association (70S formation). These results indicate that the stabilization of 70S ribosomes by paromomycin may in part be responsible for its inhibitory effects on translocation and ribosome recycling.

Flower initiation in Trifolium subterraneum L. 1. Analysis of the partial processes involved

1959 ◽  
Vol 10 (1) ◽  
pp. 1 ◽  
Author(s):  
LT Evans
Keyword(s):  
High Temperatures ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
The Other ◽  
Controlled Environment ◽  
Flower Initiation ◽  
Inhibitory Process ◽  
Inhibitory Effects ◽  
Other Hand ◽  
Short Days

The influence of various temperature and photoperiod regimes on flower initiation and flowering in eight strains of T. subterraneum has been examined, using the controlled environment facilities of the Earhart Laboratory. Flower initiation in subterranean clover appears to be under the control of three interacting partial processes, two of which are synergistic and promotive while the third is inhibitory. The promotive processes are possibly both light-independent, one being favoured by high temperatures and the other (the vernalization process) by low temperatures. The inhibitory process, on the other hand, is restricted to the diurnal dark period and is favoured by high temperatures. The interaction between the vernalization and dark inhibitory processes is such that in the absence of dark inhibition no vernalization is required by any strain, while on. the other hand sufficient vernalization can apparently overcome all dark inhibitory effects. Treatment with gibberellic acid eliminates the need for vernalization by plants of at least one early-flowering strain when. grown in short days at high temperatures. The strains of subterranean clover differ markedly in their responses to the three partial processes. In their response to the dark inhibitory process two strains are more affected by night temperature than by night length, while in two other strains the opposite is the case, which suggests that the dark inhibitory process could be resolved into more than one component.

Two forms of inhibition of spinothalamic tract neurons produced by stimulation of the periaqueductal gray and the cerebral cortex

1991 ◽  
Vol 65 (6) ◽  
pp. 1567-1579 ◽  
Author(s):  
D. X. Zhang ◽  
C. M. Owens ◽  
W. D. Willis
Keyword(s):  
Cerebral Cortex ◽  
Sural Nerve ◽  
Background Activity ◽  
Periaqueductal Gray ◽  
Afferent Input ◽  
The Other ◽  
Inhibitory Effects ◽  
Spinothalamic Tract ◽  
Other Hand ◽  
Stimulation Of

1. Recordings were made from the lumbosacral spinal cord in anesthetized macaque monkeys. The inhibitory effects of electrical stimulation of the periaqueductal gray (PAG) and the cerebral cortex or cerebral peduncle (CP) were tested and compared by recording 1) cord dorsum potentials evoked by stimulation of the sural nerve, 2) discharges recorded extracellularly, and 3) membrane potentials recorded intracellularly from spinothalamic tract (STT) neurons at rest (background activity) or in response to stimulation of the sural nerve. 2. Stimulation of the cortex or in the CP preferentially reduced the amplitude of the N1 and N2 waves of the cord dorsum potential evoked by stimulation of the sural nerve, without affecting the N3 wave. Stimulation of the PAG, on the other hand, reduced the amplitude of the N3 wave with little effect on the N1 and N2 waves. 3. The activity of 62 STT neurons was recorded extracellularly. Stimulation of the PAG or the cortex/CP inhibited nonpreferentially the responses of the neurons in the superficial laminae to all afferent inputs. On the other hand, stimulation of the PAG or the cortex/CP inhibited preferentially the responses of most STT neurons in deep layers of the dorsal horn to the small or large afferent input, respectively. 4. Thirty-five neurons were recorded intracellularly. The membrane potential of the neurons averaged -45.5 +/- 10.1 (SD) mV. All neurons were recorded in laminae III-VI; the neurons were of the wide-dynamic-range (WDR) type and had background activity. 5. The inhibitory effects of stimulation of the PAG were tested on all 35 neurons. In 32 of the neurons, stimulation of the PAG evoked a hyperpolarization. The background activity of the neurons was reduced (generally it completely ceased) by the hyperpolarization. In three neurons stimulation of the PAG did not evoke a hyperpolarization and the background activity of the neurons did not change. Nevertheless, the responses of these three neurons to afferent input were inhibited by stimulation in the PAG. 6. The inhibitory effects of stimulating the cortex and/or the CP were tested in 26 of the 35 neurons. Stimulation of the cortex and/or the CP evoked a hyperpolarization in all the neurons, although, in 10 of the 26 neurons, stimulation of the CP also evoked a depolarization. The hyperpolarization generally blocked the background activity of the neurons. 7. The effective stimuli in the PAG and the cortex/CP to evoke a hyperpolarization in STT neurons were short, high-frequency trains of pulses.(ABSTRACT TRUNCATED AT 400 WORDS)

Location of the chloride self-inhibitory site of the human erythrocyte anion exchange system

1986 ◽  
Vol 251 (1) ◽  
pp. C1-C9 ◽  
Author(s):  
P. A. Knauf ◽  
N. A. Mann
Keyword(s):  
Significant Inhibition ◽  
The Other ◽  
Inhibitory Effects ◽  
Human Red Blood Cells ◽  
Other Hand ◽  
Inhibitory Site ◽  
Osmotic Balance ◽  
A Site ◽  
Cytoplasmic Side ◽  
Very High

Experiments were performed with intact human red blood cells to determine whether the inhibitory effects of high Cl- concentrations on Cl- exchange are primarily due to interaction at the cytoplasmic or the external surface of the membrane. When internal Cl- was varied from 150 mM to 600 mM Cl- (using the nystatin technique), keeping external Cl- constant at 150 mM (with sucrose added to maintain osmotic balance), Cl- exchange was inhibited almost exactly as much as when both internal and external Cl- were increased from 150 mM to 600 mM. On the other hand, if internal Cl- was maintained constant at 600 mM, variation of external Cl- (with either sucrose, gluconate, or citrate-sucrose mixtures replacing Cl-) had no consistent effect on Cl- exchange. Even if internal Cl- was kept at 150 mM by substitution of gluconate for Cl-, an increase in external Cl- from 150 mM to 600 mM did not significantly inhibit Cl- exchange. Thus the self-inhibitory effects of Cl- seem to be caused primarily by binding to a site at the cytoplasmic side of the membrane. External Br-, on the other hand, did cause a significant inhibition of Cl- exchange. In contrast to the inhibitory effects of Cl- at neutral pH, at very high pH (around pH 11) there is an activation of Cl- exchange at very high Cl- concentrations. This effect, however, depends on binding of Cl- to an external site. Thus there seem to be at least two different low-affinity Cl- binding sites, one at the cytoplasmic side, which inhibits Cl- exchange, and one at the external side, which activates Cl- exchange at high external pH.

scholarly journals New contribution to the survey of the theory of the acrotony on the branch of one year grapevine: II - Influence of growth regulators on bud burst carried by one eye cuttings in post-dormancy stage

OENO One ◽  
2000 ◽  
Vol 34 (4) ◽  
pp. 145
Author(s):  
Béchir Ezzili ◽  
M. Bejaoui
Keyword(s):  
Growth Regulators ◽  
The Other ◽  
Bud Burst ◽  
Inhibitory Effects ◽  
Other Hand ◽  
Interesting Conclusion ◽  
Hormonal Balance ◽  
Negative Effect ◽  
One Year ◽  
New Hypothesis

<p style="text-align: justify;">Investigation of the Tunisian vineyard showed that on long canes of Muscatel of Italy, a certain percent of growing branches presents both the acrotony and basitony phenomena. The discussion of the investigation results allowed us to define a new hypothesis according to which these phenomena are controlled in part by a hormonal balance. In order to test this hypothesis, we are proceeded by studying the influence of growth regulators on bud bursting carried on one eye cuttings in one hand and on long canes to 10 units cultivated in greenhouse and in the laboratory on the other hand as well as on long wood in the vineyard. We report in this work the results relative to one eye cuttings. We applied an immersion of buds carried by one eye cuttings and in phase of post-dormancy, during 24 hours in different growth regulators at different concentrations (GA3 50 mg/l, 25 mg/l, 12.5 mg/l; ABA 25 mg/l, 12.5 mg/l, 6.25 mg/l; 6BAP 50 mg/l, 25 mg/l, 12.5 mg/l; Kinétin 50 mg/l, 25 mg/l, 12.5 mg/l; AIA, AIB, ANA 50 mg/l, 25 mg/l, 12.5 mg/l; 2-4D 10 mg/l, 5 mg/l, 2.5 mg/l). Results of these treatments show that there are generally some inhibitory effects for gibberellins and auxins. In the contrary, cytokinins possess the stimulate effects of bud bursting, applied during the end of the post dormancy phase.</p><p style="text-align: justify;">The interesting conclusion concerning the interaction of two growth regulators resides especially in the interaction cytokinin-auxins. According to our results auxins possess some inhibitory effects on the bud bursting, on the contrary, cytokinins possess a stimulate effect. The Interaction cytokinin-auxin seems to attenuate the negative effect of auxins on the bud bursting. We will see subsequently that differed applications of these regulators can give a clear demonstration.</p>

scholarly journals Effects of Sodium Azide on Sodium Fluxes in Frog Striated Muscle

1965 ◽  
Vol 48 (3) ◽  
pp. 515-525 ◽  
Author(s):  
Paul Horowicz ◽  
Carl J. Gerber
Keyword(s):  
Active Transport ◽  
Sodium Azide ◽  
Transmembrane Potential ◽  
Striated Muscle ◽  
Membrane Depolarization ◽  
The Other ◽  
Similar Increase ◽  
Other Hand ◽  
Na Efflux ◽  
Stimulation Of

Unidirectional Na fluxes from frog's striated muscle were measured in the presence of 0 to 5 mM sodium azide. With azide concentrations of 2 and 5 mM the Na efflux was markedly stimulated; the Na efflux with 5 mM azide was about 300 per cent greater than normal. A similar increase was present when all but the 5.0 mM sodium added with azide was replaced by choline. 10-5 M strophanthidin abolished the azide effect on Na24 efflux. Concentrations of azide of 1.0 mM or less had no effect on Na efflux. The Na influx, on the other hand, was only increased by 41 per cent in the presence of 5 mM NaN3. From these findings it is concluded that the active transport of Na is stimulated by the higher concentrations of azide. The hypothesis is advanced that the active transport of Na is controlled by the transmembrane potential and that the stimulation of Na efflux is produced as a consequence of the membrane depolarization caused by the azide.

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