共查询到20条相似文献,搜索用时 31 毫秒
1.
C. E. Constantinou J. L. Neubarth Monica Mensah-Dwumah 《Cellular and molecular life sciences : CMLS》1978,34(5):614-615
Summary The pacemaker properties of the various regions of isolated segments of the rabbit renal pelvis were examined. The results show that pacemaker frequency and waveform of contraction change significantly within the renal pelvis. The highest frequency was encountered at the fornix, while the ureteropelvic junction is lowest.This work was supported by NIH Grant No AM19366. 相似文献
2.
Ureteral contractions occur at intervals which are integral multiples of the period of pacemaker potentials recorded in vitro from the renal pelvis with a sucrose gap, suggesting that a gating mechanism in the pyeloureter regulates the rate at which the pacemaker initiates contractions. 相似文献
3.
C E Constantinou 《Experientia》1979,35(6):791-792
An optical detection method, using video imaging, is used to quantitatively record the frequency and velocity profile of the renal pelvis of the rabbit. It is demonstrated that concentric waves originating at the periphery of the pelvis have an initial velocity of 3.2 cm/sec, accelerating toward the pelviureteral junction reaching a final velocity of 6.4 cm/sec. 相似文献
4.
C. E. Constantinou 《Cellular and molecular life sciences : CMLS》1979,35(6):791-792
Summary An optical detection method, using video imaging, is used to quantitatively record the frequency and velocity profile of the renal pelvis of the rabbit. It is demonstrated that concentric waves originating at the periphery of the pelvis have an initial velocity of 3.2 cm/sec, accelerating toward the pelviureteral junction reaching a final velocity of 6.4 cm/sec.This work was supported by an NIH, grant No. AM 19366. 相似文献
5.
In isolated muscle strips of porcine renal pelvis and ureter, the calcium antagonist nifedipine (3.10(-7) moles/l) completely suppressed spontaneous phasic mechanical activity and the phasic components of an adrenaline-induced activation (P-component). In the presence of nifedipine, adrenaline induced in pelvis preparations (but not in the ureter) a tonic contraction (T-component) which was on average 61% of the control reaction (SD +/- 26%; n = 35). 相似文献
6.
Summary In isolated muscle strips of porcine renal pelvis and ureter, the calcium antagonist nifedipine (3·10–7 moles/l) completely suppressed spontaneous phasic mechanical activity and the phasic components of an adrenaline-induced activation (P-component). In the presence of nifedipine, adrenaline induced in pelvis preparations (but not in the ureter) a tonic contraction (T-component) which was on average 61% of the control reaction (SD±26%; n=35).The experiments were supported by a grant from the Deutsche Forschungsgemeinschaft (Go 130/20). 相似文献
7.
Summary A urinary concentrating defect was induced in Munich-Wistar rats by removing the renal pelvis from 1 kidney. This defect was partially corrected by crudely simulating the actions of pelvic wall peristalsis with a mechanical system that cyclically compressed the exposed renal papilla.A portion of this work was conducted at The Mount Desert Island Biological Laboratory, Salsbury Cove, Maine and was supported by NIH grant 2 RO1-AM15972-10 awarded to Dr B. Schmidt-Nielsen. Additional support came from the Maine and Pennsylvania Affiliates of the American Heart Association. 相似文献
8.
G. L. Avanzino D. Blanchi A. Calligaro R. Ermirio M. Fisher 《Cellular and molecular life sciences : CMLS》1981,37(12):1306-1307
Summary The crista terminalis (CT) with musculi pectinati was isolated from the right atrium: it discharged at a frequency intermediate to that of the 2 nodes. Pacemaker action potentials were recorded from the CT deep layer fibers. The results suggest the presence of a subsidiary atrial pacemaker in the CT deep layer. 相似文献
9.
Summary Section of the rabbit's proximal colon orad to thefusus coli resulted in a marked reduction in both slowwave frequency and differentiation of the two kinds of faeces produced. This indicates the existence of a pacemaker area and a mechanical role for the reversed oral-aboral gradient of the proximal colon. 相似文献
10.
D Kreitner 《Comptes rendus des séances de l'Académie des sciences. Série D, Sciences naturelles》1977,285(15):1319-1321
A technique of focal polarization allowed us to confirm that the action potentials of the true rabbit heart pacemaker cells possess a rapid sodium channel normally inactivated because of the low value of the take-off potential of this tissue. The latent pacemaker cells are regular sinocaval cells depolarized as a consequence of the proximity of true pacemaker cells. 相似文献
11.
Normally the pacemaker of the mammalian heart is located in the sinus node. In the rabbit the sinus node can be subdivided into two regions, the center of the node where the impulse originates and the border zone through which the impulse is conducted towards the atrium. Conduction properties of both regions were investigated. It appeared that conduction velocity increases and refractoriness decreases when one goes from the nodal center towards the atrium. The tissue mass of the atrium is large in comparison to the sinus node and normally the resting membrane potential of atrial fibers is more negative than that of nodal fibers; consequently, a potential difference exists causing a current flow between both areas. Evidently this hyperpolarizing current flow depresses impulse formation in the border zone fibers which have better intrinsic pacemaker properties than fibers in the nodal center. If the impulse has reached the atrium it is conducted with a relatively high safety factor and will reach the AV node in principle without difficulty. The AV node, if deprived of sinus nodal dominance, develops spontaneous activity originating from the lower nodal fibers. Also in this structure, electrotonic depression by surrounding tissue causes deceleration of the pacemaker. 相似文献
12.
F. I. M. Bonke C. J. H. J. Kirchhof M. A. Allessie A. L. Wit 《Cellular and molecular life sciences : CMLS》1987,43(10):1044-1049
Summary Normally the pacemaker of the mammalian heart is located in the sinus node. In the rabbit the sinus node can be subdivided into two regions, the center of the node where the impulse originates and the border zone through which the impulse is conducted towards the atrium. Conduction properties of both regions were investigated. It appeared that conduction velocity increases and refractoriness decreases when one goes from the nodal center towards the atrium. The tissue mass of the atrium is large in comparison to the sinus node and normally the resting membrane potential of atrial fibers is more negative than that of nodal fibers; consequently, a potential difference exists causing a current flow between both areas. Evidently this hyperpolarizing current flow depresses impulse formation in the border zone fibers which have better intrinsic pacemaker properties than fibers in the nodal center. If the impulse has reached the atrium it is conducted with a relatively high safety factor and will reach the AV node in principle without difficulty. The AV node, if deprived of sinus nodal dominance, develops spontaneous activity originating from the lower nodal fibers. Also in this structure, electrotonic depression by surrounding tissue causes deceleration of the pacemaker. 相似文献
13.
Membrane currents in cardiac pacemaker tissue 总被引:1,自引:0,他引:1
H Irisawa 《Experientia》1987,43(11-12):1131-1135
The present work is a brief survey of the mechanism of the cardiac pacemaker in sinoatrial node cells. Information on the pacemaker mechanism in cardiac tissue has been greatly enhanced by the development of the single cell isolation technique and the patch clamp technique. These methods circumvent to a large extent the difficulties involved in voltage clamping multicellular preparations. The calcium current (ICa), delayed rectifier potassium current (IK), transient outward current (Ito;IA), and the hyperpolarization activated inward current (Ih or If) were found both in whole cell preparations and in single channel analysis. The physiological significance of these currents, together with the exchange current systems for the pacemaker depolarization are discussed. 相似文献
14.
C. L. Pathak 《Cellular and molecular life sciences : CMLS》1976,32(10):1295-1297
Summary It was observed the heart rate was minimum at zero transmural pressure. The mean heart rate at zero transmural pressure was 23±5/min. This mean heart rate increased from 23±5/min to a peak value of 40±6/min (74% acceleratin) when the transmural pressure was raised from 0 to +4 mm Hg and to a similar peak value of 36±8/min (56% acceleration) when the transmural pressure was lowered from 0 to –4 mm Hg. The peak values attained at ±4 mm Hg were higly significant (p<0.001). It is concluded that the heart rate at zero transmural pressure represents the basic intrinsic pacemaker frequency independent of neural, humoral, thermal and haemodynamically induced mechanical influences. 相似文献
15.
Summary With the biogenic amines tryptamine, dopamine, and octopamine as substrates, N-acetyltransferase activity shows no detectable circadian rhythm in homogenates of whole brains of the European corn borerOstrinia nubilalis (Lepidoptera: Pyralidae). The circadian clock of this insect may be fundamentally different from the N-acetyltransferase pacemaker in the pineal gland of vertebrates. 相似文献
16.
17.
Focal and segmental glomerulosclerosis 总被引:3,自引:0,他引:3
An increasing cause of end-stage renal disease is the pathological lesion focal and segmental glomerulosclerosis (FSGS). FSGS
is characterized by proteinuria and frequently nephrotic syndrome with ensuing renal failure. The etiology remains unknown
in the majority of individuals. The idiopathic form of FSGS is most common; however, secondary forms of FSGS do exist. There
is a form of FSGS that is fulminant that frequently recurs after renal transplantation with an estimated frequency of approximately
30%, suggesting that the pathogenesis is not solely a result of intrinsic kidney disease. Recently, hereditary forms of the
disease were recognized as well as those associated with other congenital syndromes. Known genetic causes of the hereditary
form of this disease have been suggested to account for upwards of 18% of cases. This review will address recent discoveries
of the genetic mechanisms of hereditary FSGS and the current interpretations of their interactions at the slit diaphragm.
Received 17 April 2006; received after revision 23 May 2006; accepted 6 July 2006 相似文献
18.
Über eine spontane Extrasystolie im Schrittmachersystem des Tunicatenherzens (Ciona intestinalis L.)
H. Mislin 《Cellular and molecular life sciences : CMLS》1964,20(4):227-228
Summary Some experimental results on action potential (EKG) in the pacemaker system of the tunicata heart (Ciona intestinalis) are presented. Synchronous records of both end and central heart regions show a spontaneous chance of the electrical activity in the middle of the heart tube, just before the periodic reversal of the direction of the pulsating wave starts. Extra systoles in the central pacemaker influence the terminal centres and provoke reversal.
Herrn Prof.W. v. Buddenbrock zum 80. Geburtstag. 相似文献
Herrn Prof.W. v. Buddenbrock zum 80. Geburtstag. 相似文献
19.
H Reuter 《Experientia》1987,43(11-12):1173-1175
Calcium ions play a crucial role in the regulation of the heart beat. During each action potential Ca2+ ions flow into the cell and are directly and indirectly involved in generation of pacemaker potentials and of contractile force. Adrenergic and cholinergic neurotransmitters modulate Ca2+ influx. The most detailed analysis has been made on the mechanism of the beta-adrenergic effect on calcium channels in cardiac cell membranes. This is briefly summarized in a personal account, while for more detailed information the reader is referred to more extensive recent reviews. 相似文献
20.
The benzodiazepine triazolam, the benzodiazepine inverse agonist, beta-methyl carboline (beta-CCM) or both, were administered to adult male hamsters under conditions of constant light. When given alone, triazolam induced phase advances in the circadian activity rhythm of about 90 min, while beta-CCM when given alone, had no effect on phase of the activity rhythm. However, when triazolam and beta-CCM were given at the same time, the magnitude of the phase advances induced by triazolam were attenuated to about 30 min. These data, in conjunction with previous results, provide pharmacological evidence for a GABAergic system involved in the regulation of a central circadian pacemaker. 相似文献