Dual mechanisms for the low plasma levels of truncated apolipoprotein B proteins in familial hypobetalipoproteinemia. Analysis of a new mouse model with a nonsense mutation in the Apob gene.

Familial hypobetalipoproteinemia (FHbeta), a syndrome characterized by low plasma cholesterol levels, is caused by mutations in the apo-B gene that interfere with the synthesis of apo-B100. FHbeta mutations frequently lead to the synthesis of a truncated form of apo-B, which typically is present in plasma at < 5% of the levels of apo-B100. Although many FHbeta mutations have been characterized, the basic mechanisms causing the low plasma levels of truncated apo-B variants have not been defined. We used gene targeting to create a mutant allele that exclusively yields a truncated apo-B, apo-B83. In mice heterozygous for the Apob83 allele, plasma levels and the size and density distribution of apo-B83-containing lipoproteins were strikingly similar to those observed in humans with FHbeta and an apo-B83 mutation. Analysis of mice carrying the Apob83 mutation revealed two mechanisms for the low plasma levels of apo-B83. First, Apob83 mRNA levels and apo-B83 secretion were reduced 76 and 72%, respectively. Second, apo-B83 was removed rapidly from the plasma, compared with apo-B100. This mouse model provides a new level of understanding of FHbeta and adds new insights into apo-B metabolism.     

Coronary endarterectomy associated with coronary artery bypass in severe coronary artery disease. 50 cases]

The surgical indications of coronary endarterectomy were defined from a study of 50 cases in which endarterectomy was associated with aorto-coronary bypass surgery. This total represented 6 p. 100 of all the aorto-coronary bypass operations performed in the same period. Coronary endarterectomy was performed "on principal" for the right coronary artery, and "of necessity" for the left anterior descending artery. The special techniques of endarterectomy on the left anterior descending artery are described. Endarterectomy does not increase the operative risk and enables revascularisation of vessels unsuitable for bypass surgery. 85 p. 100 patients are asymptomatic with an average follow up period of 2 years after endarterectomy and aorto-coronary bypass graft of the right coronary artery.     

The activation of the contact phase of coagulation by physiologic surfaces in plasma: the effect of large negatively charged liposomal vesicles

The endogenous, negatively charged surface that induces activation of the contact coagulation factors was investigated in plasmas taken from women in late pregnancy and control subjects of child-bearing age. The plasmas from the two groups of subjects were incubated at 4 degrees C for 24 hours either in plastic or in glass tubes and the factor VII coagulant activity (VIIc) was assayed in the treated plasmas. The activation of factor VII under these conditions involves the generation of enzymes derived from factor XII (XIIa). The contact surface is rate- limiting for the activation of factor VII in the plasmas in both groups of subjects and can be supplemented by large multilamellar liposomal vesicles carrying the appropriate density of negative charge. The size of these vesicles is within the range of sizes of the large lipoprotein particles (chylomicrons, very low and intermediate-density lipoproteins). The relationship between the density of negative charge on the liposomal vesicles and VIIc was similar in the late pregnancy and the control plasmas incubated in plastic tubes. At a saturating density of negative charge the observed relative VIIc was similar in both sets of plasmas. The incubation of late pregnancy or control plasma in plastic tubes in the presence of sodium stearate caused VIIc to increase with increasing concentration of the added fatty acid. These results suggest that large lipoprotein particles carrying the appropriate free fatty acid at a sufficient density of negative charge could provide the contact surface that induces the generation of factor XIIa and the subsequent activation of factor VII. Moreover, plasmas from women in late pregnancy have a higher concentration of potential surface and a higher density of negative charge than the plasmas from nonpregnant women.     

A patient with two chronic posttraumatic aneurysms of the thoracic aorta

A case of successful replacement of two coexistent chronic post-traumatic aneurysms of the thoracic aorta is presented. Presumably, these aneurysms at the aortic isthmus and the descending thoracic aorta resulted from two different deceleration traumas.     

Assessing wound severity with color and infrared imaging of reactive hyperemia

This study examined the use of cutaneous reactive hyperemia as a means for noninvasive assessment of wound severity of newly formed temperature-modulated pressure injuries in a porcine model. Two methods to quantify the extent of the reactive hyperemic reflex were developed. First, color image analysis was used to measure the hue of injured tissue. The specific hue of the skin surface of the wounded site was found to provide an indication of the severity of the wounds. Second, infrared imaging, coupled with computer image processing, was used to detect differences in skin temperature. The relative surface temperature of the wounds showed a strong correlation with the presence or absence of deep tissue injury. Both techniques correlated with the severity of the injuries as determined by a histologic assessment of biopsied tissue, but infrared imaging provided the better means to assess wound depth.     

Clinical utility of delayed-contrast computed tomography for tissue characterization of cardiac thrombus

Among patients that present with cardiac masses, thrombus is an important diagnostic consideration that affects both clinical management and prognosis. Although thrombus can occasionally be difficult to diagnose using structural criteria alone, it can be distinguished from other structures according to tissue characteristics. Because thrombus is inherently avascular, absence of contrast uptake was used as a highly specific identifying feature. Delayed-contrast cardiac computed tomography (CT) imaging has been previously used for myocardial tissue characterization, distinguishing between viable and infarcted myocardium based upon differences in contrast uptake. This technique also offers potential diagnostic utility for assessment of thrombus. In this report, we describe a case of a patient with a giant left atrial mass in whom delayed-contrast CT was employed as a useful diagnostic technique for identification of cardiac thrombus.