Modulation of Hydra attenuata rhythmic activity: phase response curve

1976 ◽  
Vol 65 (3) ◽  
pp. 737-751
Author(s):  
C. Taddei-Ferretti ◽  
L. Cordella
Keyword(s):  
Response Curve ◽  
Phase Response Curve ◽  
Rhythmic Activity ◽  
Light Stimulation ◽  
Pulse Trains ◽  
Activity Phase ◽  
Photic Stimulus ◽  
Different Types ◽  
Hydra Attenuata ◽  
Stimulation Of

We investigated the effect of photic stimulation on the frequency of Hydra attenuata column contractions. We used positive or negative abrupt light transitions, single or repetitive light or darkness pulses, and alternation of light and darkness periods. The main results are: (a) The frequency of the contraction pulse trains (CPTs) varies transiently in response to an abrupt variation of the light intensity. (b) CPTs in progress can be inhibited by different types of photic stimuli. (c) The response time to a single photic stimulus varies during the inter-CPT interval and depends also on the polarity of the stimulus. (d) The CPTs are entrainable with repetitive light stimulation of various frequencies. (e) Long-lasting variations of the frequency of CPTs occur after the end of a repetitive light stimulation. We suggest that the mechanism responsible for the rhythym of column contractions is quite similar to that on which other biological rhythmic phenomena are based.

scholarly journals Photic phase response curve in Octodon degus: assessment as a function of activity phase preference

2000 ◽  
Vol 278 (5) ◽  
pp. R1385-R1389 ◽  
Author(s):  
Martien J. H. Kas ◽  
Dale M. Edgar
Keyword(s):  
Circadian Rhythms ◽  
Response Curve ◽  
Phase Response Curve ◽  
Activity Level ◽  
Phase Response ◽  
Octodon Degus ◽  
Photic Entrainment ◽  
Activity Phase ◽  
Subjective Night ◽  
Phase Preference

Light exposure during the early and late subjective night generally phase delays and advances circadian rhythms, respectively. However, this generality was recently questioned in a photic entrainment study in Octodon degus. Because degus can invert their activity phase preference from diurnal to nocturnal as a function of activity level, assessment of phase preference is critical for computations of phase reference [circadian time (CT) 0] toward the development of a photic phase response curve. After determining activity phase preference in a 24-h light-dark cycle (LD 12:12), degus were released in constant darkness. In this study, diurnal ( n = 5) and nocturnal ( n = 7) degus were randomly subjected to 1-h light pulses (30–35 lx) at many circadian phases (CT 1–6: n= 7; CT 7–12: n = 8; CT 13–18: n = 8; and CT 19–24: n = 7). The circadian phase of body temperature (Tb) onset was defined as CT 12 in nocturnal animals. In diurnal animals, CT 0 was determined as Tb onset + 1 h. Light phase delayed and advanced circadian rhythms when delivered during the early (CT 13–16) and late (CT 20–23) subjective night, respectively. No significant phase shifts were observed during the middle of the subjective day (CT 3–10). Thus, regardless of activity phase preference, photic entrainment of the circadian pacemaker in Octodon degus is similar to most other diurnal and nocturnal species, suggesting that entrainment mechanisms do not determine overt diurnal and nocturnal behavior.

Proprioceptive Control of the Bilaterally Organized Rhythmic Activity of the Oesophageal Neuronal Network in the Cape Lobster Jasus Lalandii

1981 ◽  
Vol 90 (1) ◽  
pp. 231-251
Author(s):  
F. NAGY ◽  
M. MOULINS
Keyword(s):  
Nervous System ◽  
Sensory Input ◽  
Phase Response Curve ◽  
Rhythmic Activity ◽  
Gastric Mill ◽  
Suboesophageal Ganglion ◽  
Motor Network ◽  
Different Parts ◽  
Stimulation Of

1. In the lobster Jasus lalandii the activity of the oesophageal nervous system (monitored through the firing of its main motor neuron, OD1) is modulated by a pair of proprioceptors, the posterior stomach receptors (PSRs). 2. The in vitro preparation used consisted of the oesophageal nervous system, the suboesophageal ganglion and the two PSRs, which provide the only source of sensory input. 3. Stimulation of a PSR activates only the oesophageal oscillator located in the ipsilateral commissural ganglion. 4. When spike conduction is blocked in the ipsilateral connective, the stimulation of a PSR activates the contralateral oesophageal oscillator. Inputs from each PSR project to the different parts of the distributed oesophageal network (in the two commissural ganglia and the oesophageal ganglion), but at a given time only one of the PSRs' projections is effective. 5. The relative efficacy of the PSRs' projections is controlled by the oesophageal motor network itself and requires that the superior oesophageal nerves be intact (sons). 6. The PSRs' inputs are integrated in the suboesophageal ganglion before reaching the oesophageal network. However, this premotor step is not involved in the control of the unilaterality of PSRs' effects. 7. The PSRs are stimulated by at least two different rhythmical muscular sequences of the foregut (the gastric mill sequence and the cardiac sac sequence) and provide a source of rhythmical inputs to the CNS. 8. The oesophageal nervous system exhibits a periodically varying sensitivity to the PSRs' inputs, which is illustrated by a phase-response curve. 9. Each oesophageal oscillator can be entrained by the rhythmical PSRs' inputs over a range of period. This range includes the period of the spontaneous gastric rhythm. 10. It is proposed that the PSRs enable the oesophageal and the gastric mill rhythms to be coordinated through a peripheral loop. The participation of PSRs in the coordination of different motor sequences of the foregut is discussed.

scholarly journals Dynamics of Structured Networks of Winfree Oscillators

2021 ◽  
Vol 15 ◽  
Author(s):  
Carlo R. Laing ◽  
Christian Bläsche ◽  
Shawn Means
Keyword(s):  
Differential Equations ◽  
Structural Property ◽  
Heterogeneous Networks ◽  
Network Structure ◽  
Response Curve ◽  
Phase Response Curve ◽  
Phase Oscillator ◽  
Interaction Function ◽  
Different Types ◽  
Low Dimensional

Winfree oscillators are phase oscillator models of neurons, characterized by their phase response curve and pulsatile interaction function. We use the Ott/Antonsen ansatz to study large heterogeneous networks of Winfree oscillators, deriving low-dimensional differential equations which describe the evolution of the expected state of networks of oscillators. We consider the effects of correlations between an oscillator's in-degree and out-degree, and between the in- and out-degrees of an “upstream” and a “downstream” oscillator (degree assortativity). We also consider correlated heterogeneity, where some property of an oscillator is correlated with a structural property such as degree. We finally consider networks with parameter assortativity, coupling oscillators according to their intrinsic frequencies. The results show how different types of network structure influence its overall dynamics.

scholarly journals Extracellular cytolysis by activated macrophages and granulocytes. I. Pharmacologic triggering of effector cells and the release of hydrogen peroxide.

1979 ◽  
Vol 149 (1) ◽  
pp. 84-99 ◽  
Author(s):  
C F Nathan ◽  
L H Brukner ◽  
S C Silverstein ◽  
Z A Cohn
Keyword(s):  
Trypan Blue ◽  
Response Curve ◽  
Target Cells ◽  
Activated Macrophages ◽  
Lymphoma Cells ◽  
Effector Cells ◽  
Proteose Peptone ◽  
Standard Assay ◽  
Different Types ◽  
J774 Cells

Lymphoma cells were rapidly lysed by activated macrophages and granulocytes in the presence of PMA. Release of 51Cr from lymphoma cells correlated closely with their destruction as viewed by scanning electron microscopy, and with reduction in the number of trypan blue-excluding cells. The standard assay involved 51 Cr release measured at 4.5 h, but injury appeared to be complete in 1 h. Of eight different types of effector cells tested, only those releasing abundant H2O2 in response to PMA were effective, that, is BCG-, C. parvum-, or casein-activated macrophages, or thioglycollate-elicited granulocytes. Normal macrophages, J774 cells, or macrophages elicited with thioglycollate broth or proteose-peptone were ineffective. BCG-activated macrophages and granulocytes caused 50% specific release of 51Cr from P388 lymphoma cells at E:T ratios between 1.4 and 4.5, and from mouse erythrocytes at E:T ratios of 0.017 to 0.025. 10 types of target cells varied widely in their susceptibility to lysis by reagent H2O2, with one-half maximal lysis occurring at H2O2 concentrations ranging from 3.63 X 10(-6) M to 3.85 X 10(-5) M. Effector cells were expected to generate approximately that much H2O2 during the period of injury. Susceptibility of the target cells to lysis by PMA-triggered granulocytes correlated closely with their sensitivity to H2O2 (r = 0.98). The membrane-active agents LPS and digitonin, which did not trigger H2O2 release, did not trigger cytotoxicity. The dose-response curve for triggering of H2O2 release by PMA was identical to that for triggering cytotoxicity. These results provided strong circumstantial evidence for the importance of H2O2 in extracellular cytolysis by activated macrophages and granulocytes when pharmacologically triggered.

Properties of Unitary IPSCs in Hippocampal Pyramidal Cells Originating From Different Types of Interneurons in Young Rats

1997 ◽  
Vol 77 (4) ◽  
pp. 1939-1949 ◽  
Author(s):  
Mohamed Ouardouz ◽  
Jean-Claude Lacaille
Keyword(s):  
Reversal Potential ◽  
Pyramidal Cells ◽  
Mean Amplitude ◽  
Paired Pulse ◽  
Young Rats ◽  
Different Types ◽  
The Mean ◽  
Paired Pulse Depression ◽  
Types Of Interneurons ◽  
Stimulation Of

Ouardouz, Mohamed and Jean-Claude Lacaille. Properties of unitary IPSCs in hippocampal pyramidal cells originating from different types of interneurons in young rats. J. Neurophysiol. 77: 1939–1949, 1997. Whole cell recordings were used in hippocampal slices of young rats to examine unitary inhibitory postsynaptic currents (uIPSCs) evoked in CA1 pyramidal cells at room temperature. Loose cell-attached stimulation was applied to activate single interneurons of different subtypes located in stratum oriens (OR), near stratum pyramidale (PYR), and at the border of stratum radiatum and lacunosum-moleculare (LM). uIPSCs evoked by stimulation of PYR and OR interneurons had similar onset latency, rise time, peak amplitude, and decay. In contrast, uIPSCs elicited by activation of LM interneurons were significantly smaller in amplitude and had a slower time course. The mean reversal potential of uIPSCs was −53.1 ± 2.1 (SE) mV during recordings with intracellular solution containing potassium gluconate. With the use of recording solution containing the potassium channel blocker cesium, the reversal potential of uIPSCs was not significantly different (−58.5 ± 2.6 mV), suggesting that these synaptic currents were not mediated by potassium conductances. Bath application of the γ-aminobutyric acid-A (GABAA) receptor antagonist bicuculline (25 μM) reversibly blocked uIPSCs evoked by stimulation of all interneuron subtypes. In bicuculline, the mean peak amplitude of uIPSCs recorded with potassium gluconate was reduced to 3.5 ± 4.4% of control ( n = 7). Similarly, with cesium methanesulfonate, the mean amplitude in bicuculline was 2.9 ± 3.1% of control ( n = 13). Application of the GABAB receptor antagonist CGP 55845A (5 μM) resulted in a significant and reversible increase in the mean amplitude of uIPSCs recorded with cesium-containing intracellular solution. Thus uIPSCs from all cell types appeared under tonic presynaptic inhibition by GABAB receptors. Paired stimulation of individual interneurons at 100- to 200-ms intervals did not result in paired pulse depression of uIPSCs. For individual responses, a significant negative correlation was observed between the amplitude of the first and second uIPSCs. A significant paired pulse facilitation (154.0 ± 8.0%) was observed when the first uIPSC was smaller than the mean of all first uIPSCs. A small, but not significant, paired pulse depression (90.8 ± 4.0%) was found when the first uIPSC was larger than the mean of all first uIPSCs. Our results indicate that these different subtypes of hippocampal interneurons generate Cl−-mediated GABAA uIPSCs. uIPSCs originating from different types of interneurons may have heterogeneous properties and may be subject to tonic presynaptic inhibition via heterosynaptic GABAB receptors. These results suggest a specialization of function for inhibitory interneurons and point to complex presynaptic modulation of interneuron function.

Enhanced coupling of adenylate cyclase to lipolysis in permeabilized adipocytes from trained rats

1991 ◽  
Vol 71 (1) ◽  
pp. 23-29 ◽  
Author(s):  
T. Izawa ◽  
T. Komabayashi ◽  
T. Mochizuki ◽  
K. Suda ◽  
M. Tsuboi
Keyword(s):  
Adenylate Cyclase ◽  
Dose Response ◽  
Response Curve ◽  
Positive Relationship ◽  
Regression Coefficient ◽  
Permeabilized Cells ◽  
Major Mechanism ◽  
The Difference ◽  
And Control ◽  
Stimulation Of

Digitonin-permeabilized adipocytes were used to study the coupling of adenylate cyclase (AC) to lipolysis in exercise-trained rats. Isoproterenol-(IPR) stimulated lipolysis in permeabilized cells was significantly greater in trained than in control rats. Under essentially identical conditions, the dose-response curve for IPR stimulation of AC activity in the absence of 3-isobutyl-1-methylxanthine was similar in trained and control rats. However, the potency of stimulation by IPR as a percentage of the basal level was greater in trained rats. AC activity and lipolysis in the presence of 3-isobutyl-1-methylxanthine were also significantly greater in trained than in control rats. Least-squares analysis by plotting the log AC vs. lipolysis values showed that the regression coefficient was about three-fold greater in trained than in control rats. The concentration of endogenous adenosine 3′,5′-cyclic monophosphate (cAMP) needed to produce a half-maximal lipolytic response was 18.58 and 10.81 pmol.min-1.10(6) cells-1 in control and trained rats, respectively. Thus a positive relationship existed between lipolysis and AC activity, with a tighter coupling in trained rats. Lipolysis in response to exogenous cAMP tended to be greater in trained than in control rats, and the difference was statistically significant for 50 microM and 10 mM cAMP. Our finding support the concept that the major mechanism of enhanced lipolysis in trained rats was an increase in the activity of enzymatic step(s) distal to cAMP.

Synchronization of two coupled pacemaker cells based on the phase response curve

2009 ◽  
Vol 4 (1) ◽  
pp. 57-66
Author(s):  
Hossein Gholizade-Narm ◽  
Asad Azemi ◽  
Morteza Khademi ◽  
Masoud Karimi-Ghartemani
Keyword(s):  
Response Curve ◽  
Phase Response Curve ◽  
Phase Response ◽  
Pacemaker Cells
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