Localization of the menaquinone-0 alkylating enzyme in the smooth reticulum of chicken liver microsomes

The alkylation of menaquinone-0 to menaquinones occurs in the microsomal fraction of chick and rat liver. Subfractionation of chick microsomes into smooth and rough reticulum was achieved by density gradient centrifugation. The alkylation enzyme was localized in the smooth reticulum with an activity of 155 pmol/mg per h, about 50-fold greater than that in the rough reticulum. The membrane-bound alkylating enzyme system requires reduced menaquinone-0 and is phospholipid-dependent.

Hydrolysis of phosphatidylethanolamine induced by nominally synthetic lysophosphoglycerides: methodological implications

Synthetic lysophosphatidylethanolamine (LPE) obtained from commercial sources augmented the apparent activity of phospholipase A2 (PLA2) in cardiac mitochondrial and microsomal fractions. For elucidation of this phenomenon, 2-[1-14C]linoleylphosphatidylethanolamine was incubated in the absence of cell protein with selected concentrations of LPE, lysophosphatidylcholine (LPC), Ca2+, ionic and nonionic detergents, and phospholipids with functional groups similar to those of LPE. Hydrolysis of phosphatidylethanolamine (PE) was evaluated by measurement of 14C-labeled free fatty acid release and confirmed by quantification of [14C]ethanolamine-labeled LPE formed. The reaction was dependent on the concentrations of Ca2+, PE, and LPE, exceeding 1.5 nmol/h with 20 micro M LPE and 30 micro M PE. Hydrolysis occurred in the presence of as little as 1 micro M LPE. PE was not hydrolyzed by comparable concentrations of ionic or nonionic detergents or by several closely related phosphatides, including LPC. Purification of synthetic LPE by high-performance LC to remove contaminating PLA2 eliminated the effect. LPE-induced hydrolysis of PE was found to depend on contamination of the LPE by PLA2 from Crotalus atrox, employed in the commercial synthesis of the lysophosphatide from the precursor used, phosphatidylethanolamine. Contamination of commercially obtained lysophosphoglycerides by PLA2 constitutes a technical pitfall which may cloud interpretation of experiments performed with inadequately purified material.

Cardiovascular trauma from angiographic jets--validation of a theoretic concept in dogs

The relationship of angiographic injections to cardiovascular trauma was determined. The aorta of dogs was studied by a mathematic model that (a) defines the kinetic energy of contrast-media jets emanating from the exit holes of catheters and (b) enables precise correlation of energy levels to potential trauma. A universal curve independent of the Reynolds number of the jet readily determines how far the jet penetrates intravascular blood. A traumatic histopathologic spectrum was found for those injections predicted by the model to be traumatic. The curve enables the angiographer to calculate the safe operating range of any catheter.

Cardiac trauma from angiographic injections. A quantitative study

To relate angiographic injections to potential cardiac trauma, we verified a mathematic theory that allows quantitative definition of the kinetic energy content of contrast jets emanating from the exit holes of angiographic catheters. Cineangiographic recordings of a range of jets of known energy content were obtained in 18 cardiac canine experiments and energy content and dissipation were quantified precisely from center line to jet edge. All contrast jets produced in clinical angiographic practice were turbulent, even those from hand injections into the coronary arteries. Energy content was related to an estimated cardiac wall damage threshold. At energy levels and damage thresholds predicted by the theory and computations, a traumatic spectrum was found by cineradiology and microscopic examination. A unique curve independent of jet Reynolds number was discovered relating the penetration of the contrast jet into the intravascular blood to the potential for cardiac trauma. This curve allowed ready calculation of hydraulic energy dissipation for any clinically used angiographic catheter and the definition of safe operational injection flow rates. Thus potential cardiac trauma can be anticipated and prevented.

A quantitative method for determining angiographic jet energy forces and their dissipation: theoretic and practical implications

Jets emanating from the exit holes of cardiac catheters during angiographic injections are theoretically capable of producing severe localized cardiovascular trauma. We adopted a fluid mechanical model of an axially symmetric jet to define these energy forces quantitatively, especially as they would occur in the clinical setting. During angiographic injection at all catheter flow rates used clinically, the jet emanating from the exit hole was always turbulent. The physical characteristics of the turbulent jet penetration into the intravascular blood fell upon a universal curve independent of the jet Reynolds number. This curve, never previously described, allows ready calculation of hydraulic energy dissipation for any catheter of known length and lumen size. The diameter of the catheter exit orifice has a greater effect than injection flow rate on decreasing jet penetration. These results provide useful guidelines for reducing trauma during routine angiography.