Protective effect of preconditioning on reperfusion induced ventricular arrhythmias of isolated rat hearts

STUDY OBJECTIVE

The aim was to investigate the effect of preconditioning on reperfusion induced arrhythmias in the isolated working rat heart.

DESIGN

Rat hearts were perfused with modified Krebs-Henseleit bicarbonate buffer. A 15 min period of global ischaemia was performed followed by a reperfusion period of 5 min. This procedure was repeated three times. Hearts were divided into the control group (n = 10) and the free radical scavenger group (n = 11). Hearts in the latter were reperfused in the presence of scavengers (SOD 3.5 x 10(4) U.litre-1 and catalase 5.0 x 10(5) U.litre-1).

EXPERIMENTAL MATERIAL

Hearts were obtained from male Sprague-Dawley rats (270-350 g).

MEASUREMENTS AND MAIN RESULTS

The incidence of reperfusion induced ventricular fibrillation in the control group decreased from 100% to 70% (NS) and to 40% (p less than 0.01) during the second and the third reperfusion periods, respectively. In the scavenger group, the incidence of ventricular fibrillation was the same in each reperfusion period at 45%. The time to onset of ventricular fibrillation increased at the second reperfusion in both groups.

CONCLUSIONS

(1) The protective effect of preconditioning on reperfusion induced arrhythmia is evident in the isolated rat heart. (2) Addition of free radical scavengers reduced the incidence of reperfusion arrhythmia. However, the protective effect of preconditioning was lost.

The role of oxygen free radicals and extracellular calcium ions in reperfusion-induced arrhythmias

To examine the role of oxygen free radicals and extracellular calcium ions in reperfusion-induced ventricular arrhythmias, we evaluated the effects of hypoxic reperfusion, oxygen free radical scavengers, allopurinol and hypocalcemic reperfusion on reperfusion-induced ventricular arrhythmias. The hearts of male Sprague-Dawley rats were perfused in the working heart mode. Whole heart ischemia was induced for 15 min and then reperfused. Rats were divided into 5 groups: control group, scavenger group, allopurinol group, hypoxia group and hypocalcemia group. Scavenger, hypoxic and hypocalcemic perfusions were undertaken only during the period of perfusion. The incidence of reperfusion-induced ventricular fibrillation (Vf) was reduced in the scavenger group (100% to 38%) and the hypoxia group (100% to 50%). Spontaneous reversion of Vf to regular sinus rhythm was recognized in the hypoxia and hypocalcemia groups. In conclusion, oxygen free radicals would play an important role in the genesis of the reperfusion arrhythmias, and extracellular calcium concentration would also play an important role in sustaining the reperfusion arrhythmias. Notably, hypoxic reperfusion had protective effects on both processes.

The levels of prostaglandins associated with the reproductive cycle of the scallop, Patinopecten yessoensis

The present experiment was undertaken to investigate the seasonal variations of levels of prostaglandins (PGs) and regulation of these levels in the ovary and hemolymph of the scallop. The levels of prostaglandin F2 alpha (PGF2 alpha) and prostaglandin E2 (PGE2) in the hemolymph and ovary increased during sexual maturation, and these levels in the ovary showed a marked increase in the spawning season. Consecutive administration of antiestrogen inhibited the increase of the levels of PGF2 alpha and PGE2 during sexual maturation. These results indicate that the seasonal variations of the levels of PGF2 alpha and PGE2 are closely related to the reproductive cycle, suggesting that PGF2 alpha and PGE2 may be involved in the sexual maturation and spawning of the scallop. Furthermore, it was supposed that estrogen likely plays a role in the regulation of PGs production in female, well known in mammals.

Evaluation of the ACR-NEMA standard for communications in digital radiology

An implementation and evaluation of a prototype multivendor communications system which complies with the American College of Radiology (ACR) and the National Electrical Manufacturers Association (NEMA) standard for communications in digital radiology is discussed. The system allows communications between interfaces from different manufacturers within a networked environment. The implementation includes network software compatible with the International Standards Organization's Open Systems Interconnect standard. The experience of the implementation effort and the evaluation of the system provide the basis for a critique of the ACR-NEMA standard. It is concluded that the ACR-NEMA standard is not well suited for application to the networked environment of picture archiving and communications systems. Two possible solutions are recommended for this problem. The first is a major revision of the existing standard. The second is the development of a family of network communications standards for digital radiology.

[Development of laser systems in the treatment of hyperpigmented skin lesions]

Laser beams have been in common use for the treatment of hyperpigmented skin lesions. However, therapeutic efficacy has been limited mainly because the output is circular with a Gaussian distribution of intensity, which makes it difficult to apply a uniformly distributed dose to the lesions. We have developed a technique whereby a laser beam is converted to have a square and uniform output intensity distribution. The principle of this technique is that the divergent laser beam enters a glass square pillar, propagates through the pillar repeating the total reflection and emerges with a uniform intensity distribution over the cross-section at the end of the pillar. The device applied this technique is incorporated in a hand-piece and both ruby and argon laser systems have been developed. The ruby laser has been used for the treatment of the melanistic skin lesions such as nevus cell nevus and nevus spilus. In clinical application, 36 of 67 cases have shown remarkably effective results with an improvement rate of 53.7%. The argon laser has been used for the treatment of vasogenic skin lesions such as portwine stain. In clinical application, 44 of 66 cases have shown effective results and the improvement rate is 66.7%. These results are excellent when compared with the other methods of treatment and with laser therapy previously used.

Membrane action of ethmozin on normoxic and hypoxic canine Purkinje fibers

Transmembrane potentials were recorded from canine Purkinje fiber preparations before and after perfusion with ethmozin (0.05, 0.2, and 1.0 microgram/ml). Under normal oxygenation (95% O2 + 5% CO2; n = 9), ethmozin at 0.05 microgram/ml significantly (p less than 0.05) reduced maximal rate of depolarization (MRD), from 750 +/- 61 to 709 +/- 58 V/s, without affecting other parameters. MRD was further decreased to 647 +/- 53 and 540 +/- 78 V/s at 0.2 and 1.0 microgram/ml of this agent. Reduction of maximal diastolic potential, from -86.1 +/- 6.0 to -84.6 +/- 5.9 mV, occurred only at 1.0 microgram/ml, suggesting that the decrease in MRD is not voltage dependent. Ethmozin significantly shortened the action potential duration at 50 (APD50) and 90% (APD90) repolarization, from 231 +/- 16 and 306 +/- 18 to 199 +/- 26 and 279 +/- 14 ms, respectively. At 1.0 microgram/ml, these values were further reduced. The effective refractory period also showed a concentration-dependent shortening, but the ratio of the refractory period to APD90 was increased. The membrane responsiveness curve was shifted by ethmozin to more negative potentials. The h infinity (inactivation of the fast Na+ current) curve was shifted by 3.8 mV to more negative values by 1.0 microgram/ml ethmozin. "Slow response" produced by high K+ + isoproterenol (0.025 microgram/ml) was not affected by ethmozin (1.0 and 5.0 microgram/ml). Ethmozin exaggerated the electrophysiologic effects of hypoxia (95% N2 + 5% CO2; n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural observation on the bacterial capsule of Bacillus anthracis seen in the spleen of a diseased cow

The bacterial capsule of Bacillus anthracis seen in the spleen of a cow which had died of anthrax was studied electron microscopically. It was visible around bacteria which had been fixed in a ruthenium red-containing fixative. It was composed of electron-dense spikes and extended outwards from the bacterial surface. It was not found around bacteria which had been treated with a fixative devoid of ruthenium red. Bacteria were seen scattered among blood cells. They were not phagocytized by neutrophils or macrophages.

A fiberscopic technique for the study of velopharyngeal closures (first report)

Velopharyngeal closures using a nasopharyngeal fiberscope and were recorded by a 16mm cine camera. The resting forms of the horizontal sections of velopharyngeal cavities were grouped into three types: the "oblate elliptical type", "prolate elliptical type" and "intermediate type". The manner and finished forms of closure were grouped into three types: the "soft palate type", "lateral wall type" and "mixed type". According to the definition, 11 out of 45 subjects studies showed the "soft palate type", eight showed the "lateral wall type" and the rest were classified as the "mixed type". There seemed to be some correlations between the closure forms and resting forms. Our method is thought to have two advantages with respect to the observation of various activities and halation-free observations.

Crystal formation of swine vesicular disease virus in porcine kidney cells (IB-RS-2 cells)

Crystal formation of swine vesicular disease virus (SVDV) in IB-RS-2 cells was studied by electron microscopy. Cells were harvested 0, 3, 3.5, 4, 4.5, 5, 6 and 7 hours after inoculation. Crystalline arrays of SVDV was first observed in the cytoplasm of a few cells 4.5 hours after inoculation. In the cytoplasm of many cells harvested at 5 hours, 1 to 3 crystalline arrays of SVDV were observed. After that, a small number of cells had crystalline arrays in the cytoplasm. The cells with crystalline arrays were rich in ribosome and polysome with dilated mitochondria and many tiny vesicles. An individual virus particle was ca. 18 nm in diameter, and the center-to-center space ca. 22 nm. Crystalline arrays varied in size depending on the plane of section.