Effects of hypoxia on atrioventricular node of adult and neonatal rabbit hearts

1989 ◽  
Vol 256 (5) ◽  
pp. H1337-H1343 ◽  
Author(s):  
M. L. Young ◽  
R. C. Tan ◽  
B. M. Ramza ◽  
R. W. Joyner
Keyword(s):  
Cycle Length ◽  
Atrioventricular Node ◽  
The Other ◽  
Adult Rabbit ◽  
Atrial Pacing ◽  
Isolated Perfused Heart ◽  
Heart Model ◽  
Perfused Heart ◽  
Av Node ◽  
The Difference

We used an isolated perfused heart model to assess the effects of graded hypoxia (95, 45, 20, 10, or 0% O2, exposure for 5 min) on the adult and neonatal (0-3 days) rabbit atrioventricular (AV) node. The AV nodal function was assessed by measuring the A-H interval at a constant atrial pacing cycle length, the longest pacing cycle length resulting in Wenckebach periodicity [Wenckebach cycle length (WCL)] and the AV nodal effective refractory period (AVNERP). The A-H intervals remained stable in neonatal hearts until O2 saturation was decreased to 10%. On the other hand, the A-H intervals began to increase in adult rabbit hearts at 20% O2. In 95% O2, the AV nodal WCL was longer in adult hearts than in the neonatal hearts (165 +/- 8 ms vs. 142 +/- 7 ms). The effect of hypoxia on the AV nodal WCL was significantly greater in adult hearts than in neonatal hearts when the O2 saturation was decreased to 20% (a 54% increase in adults vs. a 14% increase in neonates, P = 0.02). The difference was greater at lower levels of O2. In 95% O2 at comparable basis driving cycle length (240 ms), the A-H intervals were equal in neonatal and adult hearts (43 +/- 3 vs. 43 +/- 7 ms), but the AVNERP of the neonates was significantly longer than that of the adults (133 +/- 21 vs. 97 +/- 19 ms, P = 0.007).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine and hypoxia effects on atrioventricular node of adult and neonatal rabbit hearts

1987 ◽  
Vol 253 (5) ◽  
pp. H1192-H1198
Author(s):  
M. L. Young ◽  
B. M. Ramza ◽  
R. C. Tan ◽  
R. W. Joyner
Keyword(s):  
Cycle Length ◽  
Acute Hypoxia ◽  
Age Groups ◽  
Atrioventricular Node ◽  
Atrial Pacing ◽  
Perfused Heart ◽  
Av Node ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Two Age Groups

An isolated perfused heart model was used to assess the effects of hypoxia and adenosine on the adult and neonatal (1-5 days) rabbit atrioventricular (AV) node. The AV nodal function was assessed by the A-H interval at a constant atrial pacing cycle length and by the longest pacing cycle length resulting in Wenckebach periodicity. We defined the pacing cycle length at or below which the AV node demonstrated Wenckebach periodicity as the Wenckebach cycle length. Adenosine produced a smaller dose-dependent increase in A-H interval in neonates than in adults, but the increase in Wenckebach cycle length was similar in the two age groups. When the hearts were exposed to 5 min of hypoxia the increase of Wenckebach cycle length was greater for adults than for neonates. The change in Wenckebach cycle length in adults caused by hypoxia was significantly greater than that caused by 1 mM adenosine. In addition, in adults aminophylline could partially attenuate the increase in Wenckebach periodicity caused by adenosine, but aminophylline could not attenuate the increase in Wenckebach cycle length caused by hypoxia. We conclude that in the rabbit AV node 1) the adenosine effect in neonates is similar to that in adults; 2) neonates are relatively resistant to acute hypoxia compared with adults; and 3) the response to acute hypoxia in adults cannot be totally explained by the adenosine release theory.

scholarly journals Use of the Isolated Perfused Heart for Evaluation of Cardiac Toxicity

1990 ◽  
Vol 18 (4a) ◽  
pp. 497-510 ◽  
Author(s):  
Peter G. Anderson ◽  
Stanley B. Digerness ◽  
Jerald L. Sklar ◽  
Paul J. Boor
Keyword(s):  
Rat Heart ◽  
Coronary Flow ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
Heart Weight ◽  
Isolated Perfused Heart ◽  
Heart Model ◽  
Perfused Heart ◽  
Perfused Rat Heart ◽  
Isolated Perfused Rat Heart

The isolated perfused rat heart model can be used to evaluate cardiotoxicity, and is especially useful in distinguishing direct vs indirect cardiac injury. Various perfusion systems can be used to characterize the pathophysiologic as well as morphologic changes induced by drugs or chemicals of interest. The isolated perfused heart was used in the studies described herein to characterize the mechanism of allylamine cardiotoxicity. Rat hearts were perfused with Krebs-Henseleit buffer containing 10 mm allylamine and a latex balloon was inserted into the left ventricle to monitor pressure. Coronary flow in hearts perfused with 10 mm allylamine was similar to control hearts at 5, 10, and 30 min, but was reduced by 1 hr (11.5 ± 0.6 ml/min/g wet heart weight vs 16.0 ± 0.7, p < 0.01). Peak left ventricular systolic pressure increased in hearts perfused with allylamine for 5 min (156 ± 8 mm Hg vs 103 ± 9, p < 0.01), but by 2 hr was decreased compared to controls (89 ± 6 vs 105 ± 5, p < 0.05). End diastolic pressure was markedly increased at 2 hr (58 ± 3 vs 4 ± 0.8, p < 0.01). Morphologically, allylamine perfused hearts exhibited significant contraction band changes as well as numerous cells with marked swelling of the sarcoplasmic reticulum. The findings in this study suggest that allylamine produces direct myocardial damage that appears to be independent of coronary flow. These studies demonstrate that the isolated perfused rat heart model can be used to evaluate mechanisms of acute cardiotoxicity.

Common functional origin for simple and complex responses of atrioventricular node in dogs

1986 ◽  
Vol 251 (5) ◽  
pp. H920-H925 ◽  
Author(s):  
J. Billette ◽  
J. P. Gossard ◽  
L. Lepanto ◽  
R. Cartier
Keyword(s):  
Steady State ◽  
Atrioventricular Node ◽  
Sequential Patterns ◽  
Functional Domain ◽  
Conduction Time ◽  
Atrial Pacing ◽  
Av Node ◽  
Anesthetized Dogs ◽  
Atrioventricular Nodal Conduction ◽  
Transient And Steady State

The possibility that variations in atrioventricular nodal conduction time observed during transient and steady-state nodal responses share common characteristics was examined in six anesthetized dogs. Atrioventricular conduction times (AV intervals) obtained during transient (incremental atrial pacing rates, short frequency steps, and Wenckebach cycles) and steady state (periodic premature stimulation performed at 5 basic rates) responses were plotted together against the corresponding preceding ventriculoatrial (VA) intervals on a graph for each dog. Despite their diversity, nodal responses consistently resulted in AV intervals that fell within a well-defined, relatively narrow, crescent-shaped zone on the graphs. AV interval variations were small in the long VA interval range and increased slightly but predictably as the VA intervals decreased. AV intervals of transient and steady state nodal responses overlapped markedly. These results show that AV intervals of transient and steady-state nodal responses vary within a given common functional domain despite the diversity of their sequential patterns and suggest that the AV node may be obeying the same set of conduction rules during these very distinct responses.

Abstract 2200: Variability in Post-pacing Intervals Predicts Global Atrial Activation Pattern During Tachycardia

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Ilyas K Colombowala ◽  
Ali G Massumi ◽  
Abdi Rasekh ◽  
Mohammad Saeed ◽  
Jie Cheng ◽  
...  
Keyword(s):  
Cycle Length ◽  
Atrial Arrhythmia ◽  
Atrial Pacing ◽  
Activation Pattern ◽  
Activation Patterns ◽  
Cycle Lengths ◽  
Overdrive Pacing ◽  
Atrial Activation ◽  
The Difference ◽  
High Degree

Background: Knowledge of the global atrial activation pattern is critical to ablation of an atrial arrhythmia. We hypothesized that the variability in post-pacing intervals (PPI) with pacing at different cycle lengths (CL) from the same pacing site, regardless of distance to the circuit, can be used to identify atrial activation patterns during tachycardia. Methods and Results: Patients referred for ablation of SVT were included (n=28, 31 total tachycardias). During tachycardia, overdrive atrial pacing was performed. The variability in PPIs (PPIV) was calculated by comparing the difference in PPIs after overdrive pacing at trains 10, 20, and 30 ms shorter than the tachycardia cycle length (TCL). The global activation pattern was defined as circuitous (grossly visible circuit) or centrifugal (focal origin with centrifugal radiation) by electroanatomic mapping. Except for one case, all pacing was performed from the proximal CS bipole. Circuitous tachycardias exhibited minimal variability with pacing at 10 ms and 30 ms shorter than TCL (6.0±2.5 ms), whereas centrifugal tachycardias displayed a high degree of variability (56.5±20.6 ms, 8 of 14 were micro-reentrant). Rank sum analysis of PPIV suggests that the two groups are indeed distinct (P<0.001). Using PPIV cutoffs of ≤10 ms and ≥30 ms, circuitous and centrifugal activation patterns were classified with a high degree of sensitivity (94% circuitous, 92.8% centrifugal) and 100% specificity. Conclusion: Our data supports the use of PPIV to rapidly and accurately predict global activation pattern during atrial arrhythmia.

Effects of autonomic activity and changes in heart rate on atrioventricular conduction

1982 ◽  
Vol 243 (4) ◽  
pp. H523-H527 ◽  
Author(s):  
D. W. Wallick ◽  
P. J. Martin ◽  
Y. Masuda ◽  
M. N. Levy
Keyword(s):  
Vagal Stimulation ◽  
Neural Stimulation ◽  
Stimulation Frequency ◽  
The Other ◽  
Atrial Pacing ◽  
Sympathetic Stimulation ◽  
Av Node ◽  
Level Of Activity ◽  
Av Conduction ◽  
The Individual

The effects of autonomic neural stimulation and changes in atrial pacing frequency on atrioventricular (AV) conduction were determined in anesthetized open-chest dogs. Increases in vagal stimulation frequency and in pacing rate significantly increased the AV interval, whereas increases in sympathetic stimulation frequency reduced the AV interval. Vagal stimulation (1.4 Hz) prolonged the AV interval by 17 ms when the atrial pacing rate was 2 Hz. On the other hand, the same vagal stimulation increased the AV interval by 29 ms when the pacing rate was 2.73 Hz. In addition, sympathetic stimulation (1.2 Hz) reduced the AV interval by 29 ms when the pacing rate was 2 Hz. In contrast, the same sympathetic stimulation reduced the AV interval 54 ms when the pacing rate was 2.73 Hz. However, the increase in vagal stimulation did not significantly alter the positive dromotropic response of the AV node to sympathetic stimulation. Therefore, the response of AV conduction to combined sympathetic and vagal stimulation was essentially the algebraic sum of the responses to the individual stimulations. Furthermore, the level of activity in one autonomic division did not alter appreciably the interaction between the pacing rate and the activity in the other autonomic division; i.e., the interaction between pacing rate, sympathetic stimulation, and vagal stimulation was not significant.

Enhancement of ADP-induced Platelet Aggregation by Adrenaline in Vivo and Its Prevention

1973 ◽  
Vol 29 (02) ◽  
pp. 490-498 ◽  
Author(s):  
Hiroh Yamazaki ◽  
Itsuro Kobayashi ◽  
Tadahiro Sano ◽  
Takio Shimamoto
Keyword(s):  
Platelet Count ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
The Other ◽  
Endothelial Surface ◽  
Important Interaction ◽  
Blood Coagulability ◽  
The Difference

SummaryThe authors previously reported a transient decrease in adhesive platelet count and an enhancement of blood coagulability after administration of a small amount of adrenaline (0.1-1 µg per Kg, i. v.) in man and rabbit. In such circumstances, the sensitivity of platelets to aggregation induced by ADP was studied by an optical density method. Five minutes after i. v. injection of 1 µg per Kg of adrenaline in 10 rabbits, intensity of platelet aggregation increased to 115.1 ± 4.9% (mean ± S. E.) by 10∼5 molar, 121.8 ± 7.8% by 3 × 10-6 molar and 129.4 ± 12.8% of the value before the injection by 10”6 molar ADP. The difference was statistically significant (P<0.01-0.05). The above change was not observed in each group of rabbits injected with saline, 1 µg per Kg of 1-noradrenaline or 0.1 and 10 µg per Kg of adrenaline. Also, it was prevented by oral administration of 10 mg per Kg of phenoxybenzamine or propranolol or aspirin or pyridinolcarbamate 3 hours before the challenge. On the other hand, the enhancement of ADP-induced platelet aggregation was not observed in vitro, when 10-5 or 3 × 10-6 molar and 129.4 ± 12.8% of the value before 10∼6 molar ADP was added to citrated platelet rich plasma (CPRP) of rabbit after incubation at 37°C for 30 second with 0.01, 0.1, 1, 10 or 100 µg per ml of adrenaline or noradrenaline. These results suggest an important interaction between endothelial surface and platelets in connection with the enhancement of ADP-induced platelet aggregation by adrenaline in vivo.

Energy Approximation

2017 ◽  
Author(s):  
Philip Isett
Keyword(s):  
Main Lemma ◽  
The Other ◽  
Coarse Scale ◽  
Continuous Solutions ◽  
Material Derivative ◽  
Energy Variation ◽  
Energy Approximation ◽  
The Difference ◽  
Derivatives Of

This chapter presents the equations and calculations for energy approximation. It establishes the estimates (261) and (262) of the Main Lemma (10.1) for continuous solutions; these estimates state that we are able to accurately prescribe the energy that the correction adds to the solution, as well as bound the difference between the time derivatives of these two quantities. The chapter also introduces the proposition for prescribing energy, followed by the relevant computations. Each integral contributing to the other term can be estimated. Another proposition for estimating control over the rate of energy variation is given. Finally, the coarse scale material derivative is considered.

Pengaruh Unsur Budaya Lokal dalam Ungkapan Berbahasa Perancis

Metahumaniora ◽  
2017 ◽  
Vol 7 (3) ◽  
pp. 378
Author(s):  
Vincentia Tri Handayani
Keyword(s):  
Mental Representation ◽  
Cultural Context ◽  
Oral Tradition ◽  
Minimal Element ◽  
The Other ◽  
Local Culture ◽  
Community Groups ◽  
Cultural Community ◽  
The Difference ◽  
Complex Words

AbstrakFolklor yang menghasilkan tradisi lisan merupakan perwujudan budaya yang lahirdari pengalaman kelompok masyarakat. Salah satu bentuk tradisi lisan adalah ungkapan yangmengandung unsur budaya lokal dalam konstruksinya yang tidak dimiliki budaya lainnya.Ungkapan idiomatis memberikan warna pada bahasa melalui penggambaran mental. Dalambahasa Perancis, ungkapan dapat berupa locution dan expression. Perbedaan motif acuansuatu ungkapan dapat terlihat dari pengaruh budaya masyarakat pengguna bahasa. Sebuahleksem tidak selalu didefinisikan melalui unsur minimal, tidak juga melalui kata-kata,baik kata dasar atau kata kompleks, namun dapat melalui kata-kata beku yang maknanyatetap. Hubungan analogis dari makna tambahan yang ada pada suatu leksem muncul dariidentifikasi semem yang sama. Semem tersebut mengarah pada term yang diasosiasikan danyang diperkaya melalui konteks (dalam ungkapan berhubungan dengan konteks budaya).Kata kunci: folklor, ungkapan, struktur, makna idiomatis, kebudayaanAbstractFolklore which produces the oral tradition is a cultural manifestation born out theexperience of community groups. One form of the oral tradition is a phrase that containsthe elements of local culture in its construction that is not owned the other culture. Theidiomatic phrase gives the color to the language through the mental representation. InFrench, the expression can consist of locution and expression. The difference motivesreference of an expression can be seen from the influence of the cultural community thelanguage users. A lexeme is not always defined through a minimal element, nor throughwords, either basic or complex words, but can be through the frost words whose meaningsare fixed. The analogical connection of the additional meanings is on a lexeme arises fromthe identification of the same meaning. The meaning ‘semem’ leads to the associated termsand which are enriched through the context (in idiom related to the cultural context).Keywords : folklore, idioms, structure, idiom meaning, cultureI PENDAHULUAN

Rhetoric and argumentation: the unity of the field

2017 ◽  
Author(s):  
Michel Meyer
Keyword(s):  
The Other ◽  
Classic Problem ◽  
False Dilemma ◽  
The Difference ◽  
As If

Rhetoric has always been torn between the rhetoric of figures and the rhetoric of conflicts or arguments, as if rhetoric were exclusively one or the other. This is a false dilemma. Both types of rhetoric hinge on the same structure. A common formula is provided in Chapter 3 which unifies rhetoric stricto sensu and rhetoric as argumentation as two distinct but related strategies adopted according to the level of problematicity of the questions at stake, thereby giving unity to the field called “Rhetoric.” Highly problematic questions require arguments to justify their answers; non-divisive ones can be treated rhetorically through their answers as if they were self-evident. Another classic problem is how to understand the difference between logic and rhetoric. The difference between the two is due to the presence of questions explicitly answered in the premises in logic and only suggested (or remaining indeterminate) in rhetoric.

scholarly journals The Respiration of some Planktonic copepods II. The Effect Of Temperature

1953 ◽  
Vol 31 (3) ◽  
pp. 447-460 ◽  
Author(s):  
D. T. Gauld ◽  
J. E. G. Raymont
Keyword(s):  
Respiratory Rate ◽  
The Body ◽  
The Other ◽  
Effect Of Temperature ◽  
Acartia Clausi ◽  
Temora Longicornis ◽  
Different Temperatures ◽  
Planktonic Copepods ◽  
The Difference ◽  
The Relationship

The respiratory rates of three species of planktonic copepods, Acartia clausi, Centropages hamatus and Temora longicornis, were measured at four different temperatures.The relationship between respiratory rate and temperature was found to be similar to that previously found for Calanus, although the slope of the curves differed in the different species.The observations on Centropages at 13 and 170 C. can be divided into two groups and it is suggested that the differences are due to the use of copepods from two different generations.The relationship between the respiratory rates and lengths of Acartia and Centropages agreed very well with that previously found for other species. That for Temora was rather different: the difference is probably due to the distinct difference in the shape of the body of Temora from those of the other species.The application of these measurements to estimates of the food requirements of the copepods is discussed.

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