Electrophysiologic consequences of experimental acute ischemia superimposed on healed myocardial infarction in cats

Electrophysiologic studies were carried out in 61 cats studied 2 to 4 months after healing of experimental myocardial infarction, 38 cats studied 90 to 120 minutes after an acute myocardial infarction, and 24 cats in which acute myocardial infarction was superimposed on a 2 to 4 month old healed myocardial infarction (AMI/HMI). The frequency and grade of spontaneous arrhythmias, and the ability to induce sustained ventricular activity in tissue bath, were similar in the cats with acute and those with healed myocardial infarction, but greater in those with acute infarction superimposed on healed infarction. Spontaneous ventricular arrhythmias occurred in 42 percent of the cats with acute infarction, in 31 percent of those with healed infarction, and 62 percent of those with acute infarction superimposed on healed infarction. Similarly, sustained ventricular activity initiated by premature stimuli in tissue bath was achieved in 67 percent of the isolated hearts with acute infarction superimposed on healed infarction compared with 34 percent of the hearts with acute and 33 percent of those with healed infarction. The correlation between spontaneous arrhythmias and inducibility of sustained ventricular activity in tissue bath was significant in all three groups, but attained the highest level of significance in the hearts with healed infarction and those with healed and superimposed infarction.The duration of transmembrane action potentials at 90 percent repolarization (APD₉₀), recorded from surviving cells overlying an acute infarct, was shorter than that of those recorded from normal cells in the same heart. In contrast, APD₉₀ values recorded from surviving cells overlying areas of healed infarction were longer than APD₉₀ values of normal cells. Refractory periods tended to parallel action potential durations, particularly in hearts with healed or healed with superimposed acute infarction. The greatest degree of dispersion of action potential duration and refractory periods was observed in the latter hearts, which also had the greatest incidence of spontaneous arrhythmias and of inducibility of sustained ventricular activity in tissue bath.It is concluded that healing of surviving cells after myocardial infarction leaves in its wake long-term electrophysiologic cell abnormalities. These may interact with a new acute ischemic event to cause greater electrophysiologic instability than observed with acute infarction in the absence of previously injured tissue.     

导数比率法测定维磷补汁中咖啡因的含量

本文应用国产7520紫外分光光度计,用导数比率法,测定维磷补汁中咖啡因的含量。标准曲线的相关系数r=0.9996。平均回收率为100.2%,CV=0.11%。     

Spinal abnormalities in camptomelic dysplasia

Significant spinal abnormalities were found in eight patients (average age of 6 years, 5 months) with camptomelic dysplasia. The late ossification of the midthoracic pedicles served as a clear diagnostic criterion for the syndrome. Scoliosis averaging 63 degrees was found in all seven nonquadriplegic cases. Thoracic hyperkyphosis averaging 126 degrees was seen in six (75%) of the patients, while cervical kyphosis averaging 66 degrees was noted in three (38%). Vertebral body hypoplasia appeared to be a major cause of deformity. This study clarifies that patients with camptomelic dysplasia are surviving longer than previously expected and therefore should have their spinal deformities treated aggressively.     

Pulmonary cadmium oxide toxicity in the rat

Although occupational exposures to cadmium have usually involved inhalation of insoluble cadmium oxide (CdO) particles, experimental studies of pulmonary cadmium toxicity have relied on aerosol exposures to soluble cadmium chloride particles. The present study describes a model of acute lung injury based on single 3-h exposures of rats to 0.5 and 5.3 mg/m3 CdO. Biochemical changes were correlated with pathological observations for 15 d postexposure to CdO. Four days following CdO exposure, histopathological observations included focal areas of epithelial hyperplasia, a mononuclear interstitial infiltrate, and increased numbers of alveolar macrophages. In the high-dose group, these changes were correlated with increases in tissue protein and DNA contents of 217% and 195% of controls, respectively. While lungs from the low-dose exposures had returned to a normal appearance by 15 d postexposure, high-dose-exposed lungs exhibited an increase in noncellular thickening of the interstitium and a continued general hypercellularity at this time. In the high-dose exposure group, activities of the enzymes glutathione peroxidase, glutathione reductase, and the dehydrogenase of glucose 6-phosphate and 6-phosphogluconate were significantly elevated two- to fivefold at 2-4 d postexposure. When a correction was made for changes in lung cell number, significant increases were observed only in activities of the pentose-cycle dehydrogenases at 180-238% of controls. These increases suggested an enhanced ability of CdO-exposed lungs to generate the pentose-cycle products NADPH and ribose 5-phosphate, which would be needed for lipid and nucleic acid biosynthesis expected during the proliferative stages of epithelial repair. This study has demonstrated that the response to CdO exposure includes the induction of enzymatic activities that are related to antioxidant defense and lung repair.     

Regional variations in myosin heavy chain concentration after healing of experimental myocardial infarction in cats

Densitometric scanning of SDS-polyacrylamide gels was used to measure myosin heavy chain concentration in left ventricular specimens obtained from cat hearts 3 to 12 months after healing of small experimental myocardial infarctions. The study was designed to test the hypothesis that myosin concentration varies as a function of anatomic proximity to the infarct scar. Myosin heavy chain concentration was elevated in non-scarred areas adjacent to a healed infarct and normal in areas remote from the scar. The scar itself had reduced concentrations, reflecting the loss of muscle mass in this area. The increased myosin heavy chain concentration in regions adjacent to the scar may be an attempt to regulate or compensate for the decrease in mechanical function of the scarred area.     

EFFECTS OF ELECTROCONVULSIVE THERAPY ON CARDIOVASCULAR SYSTEM

Effects of electroconvulsive therapy on the pulse rate, blood pressure and electrocardiogram were studied in forty consecutive physically healthy inpatients undergoing ECT for their psychiatric disabilities. Tachycardia and elevated blood pressure occurred frequently. Sinus arrhythmias, atrial and ventricular premature beats and minor ST-T changes were also observed. All these changes reversed within thirty minutes.KEY WORDS: Electroconvulsive therapy, Cardiovascular system