Studies of Male Survivors of Myocardial Infarction: VI. The Electrocardiogram

Electrocardiograms of 101 men who survived myocardial infarction for at least three months and were free of hypertension, heart failure and other significant disease were analyzed. Within the range of 30 to 70 years, age had no apparent influence on the ECG. Six ECGs were borderline, 79 were abnormal and 16 had returned to normal. Of those with the pattern of infarction, 56 were transmural and 22 nontransmural. For all cases, posterior involvement was somewhat more common than anterior (46 to 32), but it was less common in non-transmural infarction. Ventricular premature beats, always unifocal and few in number, were the only abnormality in rhythm. Atrial fibrillation was conspicuously absent. There were four instances of complete left bundle-branch block. No evidence of left ventricular hypertrophy was seen. The clinical significance of these observations is briefly discussed.     

In vitro radiosensitivity of human diploid fibroblasts derived from women with unusually sensitive clinical responses to definitive radiation therapy for breast cancer

Between January 1985 and December 1986, 811 patients were treated for carcinoma of the breast at the Joint Center for Radiation Therapy by an identical protocol. Of these 811 patients, five patients (0.6%) were identified as having an unusually sensitive clinical response to routine external beam irradiation. This unusual clinical response was characterized by severe skin erythema and edema during the first few weeks of treatment, requiring treatment breaks. Skin fibroblast cell strains were established from these five women as well as from six women with a normal clinical response to breast irradiation (chosen at random from the population of 811 patients). Radiation survival parameters were determined by a colony formation assay from complete survival curves in coded and blinded samples. Cells from the sensitive patients were significantly more sensitive to the cytotoxic effects of radiation in vitro as determined by the parameters D0, D, D10, and n, than were the strains derived from patients with a normal response. We conclude that an unusually severe response to standard fractionated radiotherapy may be associated with greater intrinsic radiation sensitivity of the individual's somatic cells.     

Endothelin-1 and endothelin-3 stimulate calcium mobilization by different mechanisms in vascular smooth muscle.

The mechanisms by which endothelin-1 (ET-1) and endothelin-3 (ET-3) stimulate Ca2+ mobilization were investigated in rat aortic smooth muscle cells. Both ET-1 and ET-3 potently stimulated mobilization of Ca2+ from intracellular stores, however only ET-1-stimulated Ca2+ mobilization appeared to occur as a consequence of an elevation in cellular inositol trisphosphate (IP3) concentration. Neomycin, an inhibitor of phospholipase C, inhibited both the increase in [3H]IP3 formation and the mobilization of Ca2+ induced by ET-1, however it did not affect Ca2+ mobilization induced by ET-3. Together these findings indicate that ET-1 stimulates Ca2+ mobilization via an increase in IP3, whereas the effect of ET-3 appears to be mediated by a separate, IP3-independent signalling pathway.