Nonspatial determinants of electrograms in guinea pig ventricle

1981 ◽  
Vol 240 (3) ◽  
pp. C148-C160 ◽  
Author(s):  
R. P. Holland ◽  
M. F. Arnsdorf
Keyword(s):  
Guinea Pig ◽  
Transmembrane Potential ◽  
Potential Gradient ◽  
Simultaneous Recording ◽  
Electrical Circuit ◽  
Spatial Factors ◽  
Stimulus Rate ◽  
Relationship Of ◽  
The Relationship ◽  
Temperature Conduction

Theory states that the extracellularly recorded potential (epsilon) is determined by spatial and nonspatial factors. Spatial factors include the boundary between areas with different transmembrane voltages (Vm) and the relationship of the boundary to the extracellular electrode. Nonspatial factors include the Vm across the boundary [transmembrane potential gradient (TPG)] and a conductivity term (C sigma). Few studies have investigated the nonspatial factors experimentally due to the difficulty in separating the nonspatial from the spatial determinants. Our model rendered the spatial factors constant, permitted the simultaneous recording of epsilon and Vm, and allowed the manipulation of Vm and C sigma across the boundary. Epsilon and the TPG were related predictably with changes in [K+]o, [Na+]o, temperature, conduction, stimulus rate or prematurity, and hypoxia. In the presence of a constant TPG, epsilon could be affected by a change in C sigma caused by hypoxia and a metabolic poison. The effects of the nonspatial determinants on epsilon could be modeled using electrical circuit analogues. Nonspatial determinants must be considered in studies using electrocardiographic measures as an index of ischemia.

Transmembrane potential changes caused by shocks in guinea pig papillary muscle

1996 ◽  
Vol 271 (6) ◽  
pp. H2536-H2546 ◽  
Author(s):  
X. Zhou ◽  
W. M. Smith ◽  
D. L. Rollins ◽  
R. E. Ideker
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Transmembrane Potential ◽  
Potential Gradient ◽  
Resting Potential ◽  
Na Channels ◽  
Action Potential Plateau ◽  
Potential Gradients ◽  
The Relationship ◽  
Potential Plateau

To study transmembrane potential (Vm) changes (delta Vm) caused by extracellular field stimulation, Vm was recorded in 10 guinea pig papillary muscles by a double-barrel microelectrode. A 10-ms shock was delivered during the action potential plateau or during diastole. Six shock strengths (1.8 +/- 0.4, 3.8 +/- 0.7, 5.6 +/- 0.9, 7.2 +/- 1.1, 11.1 +/- 1.9, and 17.8 +/- 1.5 V/cm) were given with both polarities. The tissue was then treated with either 30 microM tetrodotoxin (TTX; n = 5) or 30 microM TTX plus Ca(2+)-free (n = 5) perfusion. For shocks during the action potential plateau, delta Vm caused by the six potential gradients was 22.4 +/- 9.6, 43.6 +/- 17.4, 54.7 +/- 17.9, 60.4 +/- 18.1, 65.4 +/- 13.7, and 66.4 +/- 12.2 mV for shocks causing depolarization and 41.1 +/- 16.5, 68.3 +/- 22, 80.5 +/- 20.4, 84.0 +/- 19.5, 93.6 +/- 16.3, and 98.9 +/- 15.4 mV for shocks causing hyperpolarization. The relationship between delta Vm and shock potential gradient was not linear. During diastole, hyperpolarizing shocks induced initial hyperpolarization, then depolarization followed again by hyperpolarization. A new depolarization upstroke occurred immediately after the shock. After TTX or TTX plus Ca(2+)-free perfusion, point stimuli 10 times diastolic threshold could not induce an action potential, but a shock field of 1.8 +/- 0.2 V/cm still induced action potentials. The peak value of depolarization measured with respect to resting potential (-87 +/- 5 mV) during the hyperpolarizing shock decreased from +14 +/- 22 before to -66 +/- 30 mV with TTX perfusion (P < 0.01). The fast upstroke rate of depolarization both during and immediately after the end of hyperpolarizing shocks was inhibited by TTX perfusion. Thus 1) the relationship between delta Vm and shock potential gradient is not linear; 2) field but not point stimulation can induce an action potential when Na+ channels are inactivated; and 3) during diastole Na+ channels are activated twice by a 10-ms hyperpolarizing shock, once during shock-induced hyperpolarization and again immediately after the end of the shock.

scholarly journals A STUDY OF THE RELATIONSHIP OF THE SCROTAL SWELLING AND RICKETTSIA BODIES TO MEXICAN TYPHUS FEVER

1930 ◽  
Vol 52 (2) ◽  
pp. 195-199 ◽  
Author(s):  
M. Ruiz Castaneda
Keyword(s):  
Guinea Pig ◽  
Guinea Pigs ◽  
Human Case ◽  
Tunica Vaginalis ◽  
Two Generations ◽  
Scrotal Swelling ◽  
Typhus Fever ◽  
Relationship Of ◽  
The Relationship

The experiments recorded above have demonstrated the following points: 1. Scrotal swelling can appear in guinea pigs directly inoculated from a human case of Mexican typhus fever. 2. In certain strains of this disease, a number of generations of guinea pigs may show absolutely no scrotal swelling, which, however, may reappear in subsequent animals, suggesting—though not absolutely proving—that the scrotal swelling is an integral part of the disease and is not due to an incidental accompanying organism. If the latter were true, one would expect the organisms that caused the scrotal swelling to disappear during the negative generations. 3. A typhus fever sustained by a guinea pig without scrotal swelling protects against the swelling upon subsequent inoculation with a strain which produces this with considerable regularity. 4. Louse passage increases the capacity of a strain to produce the scrotal lesion, probably because of the considerable accumulation of rickettsia in the louse, but in the experiment noted, even after louse passage, two generations without swelling occurred, followed by reoccurrence of the swelling. We believe that these observations, taken together, can be interpreted in favour of the likelihood that the swelling is a part of the disease and that the rickettsia-like organisms described by Mooser in the tunica vaginalis have etiological significance.

Distribution of Glutamine Metabolizing Enzymes and Production of Urinary Ammonia in the Mammalian Kidney

1958 ◽  
Vol 195 (2) ◽  
pp. 316-320 ◽  
Author(s):  
Roland W. Richterich ◽  
Leon Goldstein
Keyword(s):  
Enzyme Activity ◽  
Glutamine Synthetase ◽  
Guinea Pig ◽  
Mammalian Species ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Outer Medulla ◽  
Metabolizing Enzymes ◽  
Relationship Of ◽  
The Relationship

The distribution of the glutamine metabolizing enzymes was studied in the kidney of four mammalian species (dog, rat, rabbit and guinea pig). Glutaminase I activity of whole kidney was highest in the dog (19.1 µm NH3/gm/min.), intermediate in the rat (8.1 µm NH3/gm/min.), and low in the guinea pig (1.1 µm NH3/ gm/min.) and rabbit (0.6 µm NH3/gm/min.). In all four species, enzyme activity was highest in the cortex and inner medulla. Glutaminase II and glutamine synthetase activity were lower than glutaminase I activity in all four species. Both glutaminase II and glutamine synthetase activity were found only in the cortex and outer medulla. The relationship of the glutamine metabolizing enzymes to the production of urinary ammonia is discussed.

Heterophil antigens in Ehrlich ascites fluid

1969 ◽  
Vol 15 (12) ◽  
pp. 1409-1413 ◽  
Author(s):  
C. P. Eng ◽  
J. A. Hindmarsh ◽  
J. F. Morgan
Keyword(s):  
Guinea Pig ◽  
Liver Extract ◽  
Heat Stability ◽  
Ascites Fluid ◽  
Heat Stable ◽  
Ehrlich Ascites ◽  
Kidney Enzyme ◽  
Ehrlich Ascites Cell ◽  
Relationship Of ◽  
The Relationship

Immunodiffusion and hemagglutination tests have demonstrated that antiserum against Ehrlich ascites fluid is active against tissue saline extracts and erythrocytes of the mouse, rat, guinea pig, hamster, and cat. Detailed studies have shown that cat liver extract shares a common antigen present in the Ehrlich ascites cell, normal mouse liver, and guinea pig kidney. Enzyme susceptibility and heat stability tests have indicated that the cat heterophile antigen is heat stable and protein in nature. The relationship of this new heterophile antigen with other identified heterophile antigens is discussed.

scholarly journals The release of an endogenous pyrogen from guinea pig leukocytes in vitro: a new model for investigating the role of lymphocytes in fevers induced by antigen in hosts with delayed hypersensitivity.

1977 ◽  
Vol 145 (5) ◽  
pp. 1288-1298 ◽  
Author(s):  
P Chao ◽  
L Francis ◽  
E Atkins
Keyword(s):  
Guinea Pig ◽  
Guinea Pigs ◽  
Polymorphonuclear Leukocytes ◽  
Delayed Hypersensitivity ◽  
Endogenous Pyrogen ◽  
Phagocytic Cells ◽  
Relationship Of ◽  
The Relationship

Guinea pig periotoneal exudate (PE) cells incubated overnight in vitro with heat-killed Staphylococci released an endogenous pyrogen (EP) that could be assayed by intravenous injection in rabbits. The febrile responses were linearly related to the dosage of EP over an eightfold range. PE cells derived from guinea pigs with delayed hypersensitivity (DH) to bovine gamma globulin (BGG), also released EP when incubated with antigen in vitro. This reaction was specific and did not occur withe PE cells from normal or complete Freund's adjuvant-sensitized guinea pigs. Studies indicated that monos and/or polymorphonuclear leukocytes rather than lymphocytes were the source of EP. However, when incubated with BGG and sufficient dosages of BGG-sensitized lymphocytes, normal PE cells released EP over a 42 h period. These results suggest that antigen stimulates specifically sensitized lymphocytes to release an agent (perhaps a lymphokine) that activates phagocytic cells to release EP. This model offers unique advantages for investigating in vitro the role of the lymphocyte in antigen-induced fever in DH as well as the relationship of this lymphocyte-induced activity to other known biologic activities mediated by antigen stimulated lymphocytes.

Modulation of myocardial function and [Ca2+] sensitivity by moderate hypothermia in guinea pig isolated hearts

1999 ◽  
Vol 277 (6) ◽  
pp. H2321-H2332 ◽  
Author(s):  
David F. Stowe ◽  
Satoshi Fujita ◽  
Jianzhong An ◽  
Richard A. Paulsen ◽  
Srinivasan G. Varadarajan ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Myocardial Function ◽  
Mild Hypothermia ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Moderate Hypothermia ◽  
Isolated Hearts ◽  
Intracellular Ca ◽  
Relationship Of ◽  
The Relationship

Cardiac hypothermia alters contractility and intracellular Ca2+ concentration ([Ca2+]i) homeostasis. We examined how left ventricular pressure (LVP) is altered as a function of cytosolic [Ca2+]iover a range of extracellular CaCl2 concentration ([CaCl2]e) during perfusion of isolated, paced guinea pig hearts at 37°C, 27°C, and 17°C. Transmural LV phasic [Ca2+] was measured using the Ca2+ indicator indo 1 and calibrated (in nM) after correction was made for autofluorescence, temperature, and noncytosolic Ca2+. Noncytosolic [Ca2+]i, cytosolic diastolic and systolic [Ca2+]i, phasic [Ca2+]i, and systolic Ca2+ released per beat (area Ca2+) were plotted as a function of 0.3–4.5 mM [CaCl2]e, and indexes of contractility [LVP, maximal rates of LVP development (+dLVP/d t) and relaxation (−dLVP/d t), and the integral of the LVP curve per beat (LVParea)] were plotted as a function of [Ca2+]i. Hypothermia increased systolic [Ca2+]iand slightly changed systolic LVP but increased diastolic LVP and [Ca2+]i. The relationship of diastolic and noncytosolic [Ca2+] to [CaCl2]ewas shifted upward at 17°C and 27°C, whereas that of phasic [Ca2+]ito [CaCl2]ewas shifted upward at 17°C but not at 27°C. The relationships of phasic [Ca2+]ito developed LVP, +dLVP/d t, and LVParea were progressively reduced by hypothermia so that maximal Ca2+-activated LVP decreased and hearts were desensitized to Ca2+. Thus mild hypothermia modestly increases diastolic and noncytosolic Ca2+ with little effect on systolic Ca2+ or released (area) Ca2+, whereas moderate hypothermia markedly increases diastolic, noncytosolic, peak systolic, and released Ca2+ and results in reduced maximal Ca2+-activated LVP and myocardial sensitivity to systolic Ca2+.

True transmembrane potential curve from the surface of guinea pig ventricle: its relation to intrinsic deflection

1960 ◽  
Vol 198 (5) ◽  
pp. 975-980 ◽  
Author(s):  
Gordon E. Dower ◽  
Margaret A. Geddes
Keyword(s):  
Guinea Pig ◽  
High Speed ◽  
Direct Relationship ◽  
Transmembrane Potential ◽  
Reference Electrode ◽  
Potential Curve ◽  
Sodium Ions ◽  
Wire Loop ◽  
Definition Of ◽  
The Relationship

The monophasic curves of the potential variations between an intracellular microelectrode and a remote reference electrode when recorded at sufficiently high speed show irregular upstrokes which are made up of a steep rise and one, or more, gentle rises; the relationships between these rises vary with position on the surface of the (guinea pig) ventricle. By subtracting, electronically, the local ECG obtained from a wire-loop electrode surrounding the microelectrode the irregularities can be removed: the subtractor output yields monophasic curves with even, sigmoid upstrokes. Such curves represent the true transmembrane potential. The use of the subtractor brings out the relationship between the intrinsic deflection of the local ECG and the upstroke of the transmembrane potential curve. Because these coincide and because the latter marks the influx of sodium ions into the cell, a direct relationship between the intrinsic deflection and the entry of sodium is revealed. This adds to the significance of the intrinsic deflection and permits a more rigorous definition of it.

Sign in / Sign up

Export Citation Format

Share Document