摘要:

Effects of MJ 1999 (1 × 10-9M to 1 ×10-2M) on rabbit right atrial and canine Purkinje fiber preparations were studied. MJ 1999 had a pA2of 6.1 against the chronotropic effect of isoproterenol on rabbit SA node. Significant slowing first occurred with MJ 1999 at 1 × 10-4M. The spontaneous firing rate of Purkinje fibers in vitro did not change significantly after exposure to MJ 1999 1 × 10-4M. Idioventricular rate was slowed and idioventricular escape time was prolonged in dogs with atrioventricular block after MJ 1999, 2.0 mg/kg. MJ 1999, 1 × 10-7M to 5 × 10-4M, had no effect on resting potential, overshoot and amplitude of phase 0 of transmembrane potentials (TMP) recorded from canine ventricular muscle, canine Purkinje fibers or rabbit atrial fibers nor did it affect phase 0 Vmaxof TMP recorded from the Purkinje or atrial fibers. Similar concentrations of MJ 1999 had no effect on membrane responsiveness in Purkinje fibers. In Purkinje fibers, control action potential duration (APD) was 325 msec and the effective refractory period (ERP) 277 msec. MJ 1999, 1 × 10-3M, increased the APD to 470 msec and ERP to 404 msec. In ventricular muscle fibers, APD was 230 msec and the ERP was 223 msec, under control conditions. MJ 1999, 1 × 10-3M, increased the APD to 281 msec and ERP to 267 msec. Changes in APD and ERP induced by MJ 1999 were magnified at slower rates of stimulation. The effects of MJ 1999 on both APD and ERP were more marked in Purkinje fibers than in ventricular muscle fibers. The effects of MJ 1999 on phase 0 of the TMP and on repolarization and refractoriness of the TMP differ markedly from those seen with quinidine, procainamide, and lidocaine.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Morphologically intact muscle cells were prepared by perfusing adult rat hearts with a balanced salt medium containing 0.1% collagenase and 0.2% hyaluronidase. Yields of intact cells representing up to 25% of the weight of the heart were obtained. The cells separated along the line of the intercalated discs, with cleavage of desmosomes but with tearing of the plasma membrane in the region of the gap junction, so that when two contiguous cells were parted, the gap junction was retained intact attached to one of the cells. The fine structure of undamaged cells was indistinguishable from that of normal myocardial cells in situ, whereas damaged cells characteristically revealed numerous cytoplasmic vacuoles, clumping of myofilaments, and blebbing of the cell membrane, but morphologically normal mitochondria. The earliest lesion detected was a dilatation of the T (transverse tubular) system.Respiration in the intact cells was linear for 30 to 60 minutes and approximately two to three times the rate observed with heart muscle slices or the arrested isolated perfused heart. Oxygen uptake was stimulated by pyruvate but not by lactate. These observations demonstrate the feasibility of preparing intact isolated cells from adult rat heart and their potential value in histologic, pharmacologic, and metabolic studies.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

In five dogs (18 to 28 kg) under pentobarbital anesthesia metal clips were placed on the free margin of the anterior and posterior mitral valve leaflets, and on the epicardial surface of the left ventricle at the apex and at the base. After full recovery cineangiograms were taken in the right anterior oblique and right lateral position and the length from the apex of the left ventricle to the free margins of the mitral valve leaflet was measured. The average distance between the apex and the free margin of the anterior leaflet in two dogs and on a clip placed on the chordae tendineae above the anterior leaflet in two dogs was the same during slow ventricular filling, atrial systole, and during ventricular ejection. The average distance between the apex and the free margin of the posterior leaflet in three dogs was also the same during the same time periods in the cardiac cycle. The maintenance of the same distance between the free margin of the mitral valve leaflet and the apex during diastole when the papillary muscle is relaxed and during systole when it is contracted suggests that the papillary muscle contracts isometrically.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Arterial pressure, portal pressure, hepatic venous pressure, and hepatic volume were measured simultaneously in anesthetized cats. When hepatic venous pressure was raised, hepatic volume increased at first rapidly then slowly. After 20 minutes, the volume increased at a steady rate which continued for at least 4 hours. During this period, the hepatic blood volume (51Cr-tagged red blood cells) was constant, and fluid with a high protein content accumulated in the plethysmograph. When the hepatic lymphatics were tied, the rate of filtration (0.060 ± 0.003 ml · min-1· mm Hg-1· 100 g-1) was directly proportional to the hepatic venous pressure. When hepatic venous pressure was restored to zero, the filtered fluid was not reabsorbed by the liver. The data are discussed in relation to Starling's hypothesis and the formation of ascites. It is concluded that transsinusoidal fluid filtration in the liver is dependent on the sinusoidal hydrostatic pressure and that no protective mechanisms are available to prevent filtration when hepatic venous pressure is raised for long periods.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

The present experiments describe effects of transient increases in heart rate on ventricular pacemakers during digitalization. Fifteen anesthetized, vagotomized dogs were studied during ouabain infusion or after recovery from ouabain-induced ventricular tachycardia. Vagal stimulation was used to assess baseline ventricular automaticity and 30-second periods of atrial pacing were utilized to evaluate the response of ventricular pacemakers following different increments in rate. After an average dose of 45 ± 3 (SE) μg/kg of ouabain, vagal stimulation unmasked an automatic ventricular focus in 14 animals and pacing was followed by ventricular acceleration in all 15 animals. The Degrees of ventricular acceleration varied directly with the pacing rate. The increment in ventricular rate above the level unmasked by vagal stimulation averaged 59 ± 4% of the increment in atrial rate. At the higher driving rates, a transient postpacing depression was present before the emergence of a rapid ventricular focus. These findings were unaffected by beta-receptor blockade with 4-(2-hydroxy-3-isopropylamino propoxy) acetanilide (AY21,011). The results indicate that transient increases in heart rate may accelerate rather than depress ventricular pacemakers during digitalization.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Infusions of hypertonic dextrose or NaCl solutions reduce resistance in several vascular beds of experimental animals. To study the response in man, 60 intrabrachial arterial jet infusions of hypertonic dextrose solution or hypertonic NaCl solution, each at 3 dose levels (1, 2, and 4 milliosmols/min), were made in 19 male student volunteers aged 21 to 29 years. Limb blood flow was measured by continuous infusion indicator-dilution, and vascular resistance calculated as mm Hg/ml flow/100 cm3limb vol/min. Measured increases in ipsilateral cephalic venous plasma osmolarity and serum dextrose and sodium concentrations during hypertonic infusions ranged from 7 to 30 milliosmols/liter, 153 to 481 mg/100 ml and 4 to 19 mEq/liter, respectively. Measured limb venous blood hematocrit during hypertonic infusions was similar to that during control isotonic infusions. All 60 hypertonic infusions evoked an increase in limb blood flow and decrease in limb vascular resistance as compared to “resting” values during paired control isotonic NaCl infusions. There was a significant (P<.01) positive linear correlation between level of initial vascular resistance and magnitude of response to all hypertonic infusions. At each dose level, neither regression coefficient nor regression adjusted mean response to dextrose was significantly different from that to hypertonic NaCl (P>.05).The results of these studies indicate that the local vascular response to hypertonicity in the limb of man is a decrease in resistance, the magnitude of which is a function of the level of plasma osmolarity and the level of initial limb resistance. The steady-state responses to hypertonic dextrose are quantitatively similar to those to hypertonic NaCl.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Dogs were anesthetized with α-D (+)-glucochloralose. After bleeding to a mean arterial pressure of 55 mm Hg, blood flow in subcutaneous adipose tissue decreased from 6 ± 0.9 (mean ± SE) to 0.6 ± 0.21 ml/min/100 g (P < 0.001), and remained at that low level during bleeding to 35 mm Hg for an additional 90-minute period. In five out of nine experiments the blood flow ceased completely. Sixty minutes after reinfusion, the blood flow was significantly lower than control, and in two there was no blood flow after reinfusion. In animals previously treated with phenoxybenzamine (5 mg/kg), the decrease in blood flow was significant only at 35 mm Hg arterial pressure (2.6 ± 0.67 ml/min/100 g). After reinfusion blood flow increased to a mean above 10 ml/min/100 g, significantly higher than resting blood flow (P < 0.05). There was no significant change in arterial FFA concentration or FFA release in subcutaneous adipose tissue during bleeding and after reinfusion. In phenoxybenzamine-treated animals there was a tendency to have higher arterial FFA concentration and FFA release. The oxygen uptake fell from 0.47 ± 0.07 to 0.13 ± 0.05 ml/min/100 g (P<0.01) during 55 mm Hg arterial pressure and remained significantly lower also during 35 mm Hg arterial pressure. Previous treatment with phenoxybenzamine prevented a fall in O2uptake in subcutaneous adipose tissue. The decrease in blood flow in subcutaneous adipose tissue during bleeding was more pronounced than found in other organs with same hemorrhagic shock procedure. After reinfusion, flow in subcutaneous adipose tissue could not be restored, indicating irreversible vascular damage, α-receptor activity seems to play a significant part in the development of vascular and metabolic changes in subcutaneous adipose tissue during bleeding.

ISSN:0009-7330    

出版商:OVID    

年代:1970

数据来源: OVID