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At least 343 records · Page 19Linked to original sources
PubMed1975

Left and right heart haemodynamics during spontaneous angina pectoris. Comparison between angina with ST segment depression and angina with ST segment elevation.

The function of both right and left sides of the heart was studied during spontaneous attacks of angina pectoris at rest in 7 patients showing ST depression (type I) and 4 showing ST elevation (type II) during the attack. In none of the 44 type I attacks and 29 type II attacks which were recorded did circulatory changes; the latter were different in the two groups. Type I attacks showed: a) a brief fall in arterial pressure, accompanied by b) a rise of right atrial and pulmonary wedge pressures and c) a decrease of cardiac output, right and left stroke work, the mean rate of systolic ejection, and indirect left ventricular pre-ejection dP/dt. In the course of the attack a hypertensive phase followed, which was paralleled by an increase of heart rate, cardiac output, left and right stroke work, and mean systolic ejection rate, left dP/dt; right atrial pressure and wedge pressure remained raised. All of the circulatory functions started to revert towards the pre-attack levels coincident with the waning phase of the electrocardiographic alteration, the latter occurring either spontaneously or after nitroglycerin. Type II attacks for the entire duration of the electrocardiographic changes showed: a) a reduction of arterial pressure, cardiac output, right and left stroke work, mean systolic ejection rate, and left dP/dt, b) a rise of right atrial and wedge pressures, and c) quite small changes of heart rate. When the electrocardiogram started to revert to the pre-attack aspect, the cardiac function rapidly improved and, after a supernormal phase, returned to the basal levels in about 2 minutes. It is concluded: 1) that no circulatory factor interfering with the mechanical effort of the heart is responsible for eliciting spontaneous angina: 2) that in type I attacks right and left ventricular impairment occurs which recovers rapidly, possibly through a sympathetic compensation; 3) that in type II attachs dysfunction of both sides of the heart occurs and persists throughout the episode of electrocardiographic alteration; 4) that the dynamic impairment is probably more severe in type I than in type II angina.

Angina Pectoris↗
PubMed1997

Regulation of segmentation and segmental identity by Drosophila homeoproteins: the role of DNA binding in functional activity and specificity.

Recent advances have shed new light on how the Q50 homeoproteins act in Drosophila. These transcription factors have remarkably similar and promiscuous DNA-binding specificities in vitro; yet they each specify distinct developmental fates in vivo. One current model suggests that, because the Q50 homeoproteins have distinct biological functions, they must each regulate different target genes. According to this 'co-selective binding' model, significant binding of Q50 homeoproteins to functional DNA elements in vivo would be dependent upon cooperative interactions with other transcription factors (cofactors). If the Q50 homeoproteins each interact differently with cofactors, they could be selectively targeted to unique, limited subsets of their in vitro recognition sites and thus control different genes. However, a variety of experiments question this model. Molecular and genetic experiments suggest that the Q50 homeoproteins do not regulate very distinct sets of genes. Instead, they mostly control the expression of a large number of shared targets. The distinct morphogenic properties of the various Q50 homeoproteins may principally result from the different manners in which they either activate or repress these common targets. Further, in vivo binding studies indicate that at least two Q50 homeoproteins have very broad and similar DNA-binding specificities in embryos, a result that is inconsistent with the 'co-selective binding' model. Based on these and other data, we suggest that Q50 homeoproteins bind many of their recognition sites without the aid of cofactors. In this 'widespread binding' model, cofactors act mainly by helping to distinguish the way in which homeoproteins regulate targets to which they are already bound.

Animals↗