Usefulness of ambulatory radionuclide monitoring of left ventricular function early after acute myocardial infarction for predicting residual myocardial ischemia.

Ambulatory radionuclide monitoring of left ventricular function was performed with the nuclear Vest device in 35 patients early after acute myocardial infarction. Patients were evaluated during post-infarction treadmill, other activities that included mental stress and cold pressor challenge, and with stress thallium imaging and cardiac catheterization. Of the 35 patients evaluated, 14 had ischemic responses on treadmill testing and 21 had negative responses. By contrast, 20 had redistribution by thallium imaging suggesting ischemia. Vest studies demonstrated 56 responses suggestive of ischemia in 23 patients. Twenty-two occurred during exercise and 13 with mental stress. Seventy-five percent were silent and only 39% had associated electrocardiographic changes. Vest responses were compared in patients whose thallium scan was indicative of ischemia (thallium-positive) and those without ischemia (thallium-negative). Ejection fraction was higher in the thallium-positive group (0.52 +/- 0.11), as compared with thallium-negative patients (0.44 +/- 0.1). With exercise, ejection fraction decreased for the thallium-positive patients from 0.52 +/- 0.11 to 0.40 +/- 0.09 at peak exercise. For thallium-negative patients, ejection fraction changes were not significant. During mental stress, ejection fraction decreased from 0.51 +/- 0.11 to 0.45 +/- 0.12 for thallium-positive patients while thallium-negative patients were unchanged. Vest-measured decreases in ejection fraction of greater than or equal to 5 units during exercise were highly sensitive (90%), specific (73%) and predictive (82%) of a positive thallium scan. The same response for mental stress was specific (87%) and predictive (85%) of a positive scan result.(ABSTRACT TRUNCATED AT 250 WORDS)

Repair of radiation damage in noncycling parenchymal hepatocytes.

The purpose of this study was to determine whether parenchymal hepatocytes in G0 are able to repair potentially lethal damage. The survival curve for hepatocytes assayed immediately after X irradiation was found to have an extrapolation number, n, which was not significantly different from unit, and a D0 equal to 2.7 Gy. In contrast, when irradiated hepatocytes were allowed to remain in situ for 24 h before being assayed for their reproductive survival , the n value significantly increased to 2.3, whereas the D0 value remains unchanged. But parenchymal hepatocytes are able to repair potentially lethal damage and it is expressed exclusively as an increase in the extrapolation number.

Isolation, culture, and transplantation of human hepatocytes.

The in situ two-step collagenase perfusion technique used for the isolation of hepatocytes from rat liver was adapted into a procedure applicable to pieces of human liver obtainable from surgical procedures. Human hepatocytes obtained by this method were maintained in primary culture for 10 days. The cellular changes observed at the light microscopic and electron microscopic levels are described. The changes in microsomal enzymes as a function of the age of the cultures were also measured. Exposure of the human hepatocytes to procarcinogens known to be metabolized by rodent liver resulted in unscheduled DNA synthesis. The isolated hepatocytes were also transplanted into two-thirds partially hepatectomized athymic nude mice. The transplanted cells formed nodules with characteristic hepatic architecture. These studies demonstrate that hepatocytes obtained from human liver by the described modified collagenase technique can be used for in vitro studies in chemical carcinogenesis.

Transplantation system for determining the clonogenic survival of parenchymal hepatocytes exposed to ionizing radiation.

An in vivo transplantation technique has been developed which can be utilized to determine the reproductive survival of parenchymal hepatocytes exposed either in vitro or in vivo to both physical and chemical genotoxic agents. We have used this assay system to determine the survival of liver cells exposed to sparsely ionizing radiation. The D0 value of the survival curve was 249 rads and the extrapolation number was 1.2. These results indicate that hepatocytes irradiated while in the G0 phase are unable to accumulate sublethal damage to an appreciable extent if they are stimulated to undergo replication within 24 hr after the infliction of the damage.