Post-exercise changes of the Q-Tc interval in coronary heart disease

A study was made of variations of the Q-Tc interval as a result of exercise on 40 subjects, all submitted to coronary-angiography. The exercise tests were carried out on an ergometric bicycle and the Q-T interval, corrected for heart rate according to Bazett's formula, was measured on the resting ECG before the start of the test, and on the ECG recorded immediately following the end of the exercise. Of the 40 subjects, 29 had coronary heart disease and 11 were considered normal or showed non-significant lesions. In these 11, except for one with left bundle branch block, the Q-Tc showed a shortening on the ECG following exercise. Of the patients with coronary heart disease with or without the presence of contractility disturbances, 20 showed a prolongation of the Q-Tc following exercise, and eight showed no change. The Q-Tc variations were 0.05 sec. +/- 0.03. Analyzing the data as a 2 X 2 contingency table, the value of the alpha 2 corrected for continuity is 30.4, which is highly significant. Our study thus revealed that Q-Tc variations with exercise have a value for the diagnosis of coronary heart disease in exercise tests.

The rate pressure product: fact of fallacy?

The product of heart rate and blood pressure, (HR x BP), index of the myocardial oxygen consumption, was evaluated on 37 individuals with ages of between 32 and 65 years; 24 had ischemic heart disease with a disease of 1, 2 or 3 vessels, and 13 had non-significant lesions of 1 vessel (less than 75%) or no coronary heart disease (CHD). From the HR x BP correlation with the study of the angiograms of the coronary arteries, we verified that there was no distinction between patients. with CHD with or without an ejection fraction less than 50% or, with or without disturbances of myocardial contractility, and normal individuals. Thus, we believe that in patients with CHD, an excessive increase in the oxygen requirements of the myocardium is not the sole pathogenic mechanism of ischemia.

Experimental Yersinia pestis infection in rodents after intragastric inoculation and ingestion of bacteria

To clarify the pathogenesis of oral plague infection, we studied the susceptibility of three species of rodents to intragastric inoculation of Yersinia pestis, described the pathology and progression of infection, and measured antibody responses to fraction IA antigen of Y. pestis. The 50% lethal doses of bacteria by intragastric inoculation for Mus musculus, Zygodontomys pixuna, and Rattus rattus were log10 = 6.32, 5.46, and 9.62, respectively, which were at least 1,000-fold higher than the values obtained by subcutaneous inoculation. M. musculus was shown to be susceptible to lethal infection also when bacteria were ingested in drinking water. Microscopic pathology was consistent with heavy systemic infection. Quantitative cultures of tissues at different times after intragastric inoculation revealed that infections of blood, liver, and spleen preceded infections of Peyer's patches and mesenteric lymph nodes. Stool cultures were negative. The strain of Y. pestis used for inoculation was killed when exposed to a buffered solution at pH less than or equal to 3. Antibody responses were observed in some of the surviving rodents after intragastric challenge. These results showed that Y. pestis was an effective oral pathogen that produced fatal systemic infections and self-limited infections with immunity but did not produce enteric pathology or lead to fecal excretion of bacteria.

A control and data processing instrument for kidney tubule research

A microprocess-based instrument has been designed to facilitate research on the electrical properties of isolated renal tubules. Because of the high correlation between the electrical and ionic properties of tubules, this research helps in understanding the mechanisms of reabsorption and secretion along the many functionally different segments of a renal tubule. By replacing manual methods of control, measurement, and calculation, this instrument expedites the experimental procedure and adds accuracy and flexibility not available in the previous arrangement. Based on operational directives entered by the user, the instrument controls the number, frequency, polarity, intensity, and duration of current pulses through the tubule preparation and records the steady-state voltages induced at either end of the tubule. Then, using a transmission line model, it calculates and displays tubule parameters for each current pulse. The diameter of the tubule, as calculated from the model equations, is of immediate interest to the investigator. How well this figure compares with the physical diameter is an indication of the integrity of the preparation and the validity of the other calculations.