Interferon-γ signal transduction during parasite infection: modulation of MAP kinases in the infection of human monocyte cells (THP1) by Toxoplasma gondii

We assayed mitogen-activated protein (MAP) kinase phosphorylation in a human monocyte cell line (THP1) during their infection by Toxoplasma gondii . In addition, we tested the effect of specific MAP kinase inhibitors (PD098059 and SB203580) on parasite invasion. MAP kinase phosphorylation was increased in the cytosol and membrane fractions of THP1 infected with T. gondii . The MAP kinase phosphorylation of uninfected THP1 cells was not significantly modified by incubation for 20 h with 1000 U/ml of IFN-γ. However, IFN-γ treatment of infected cells significantly reduces the increase in phosphorylation caused by parasite infection. There was also MAP kinase activity in the cytosol and membrane fractions of extracellular T. gondii tachyzoites. IFN-γ altered the distribution of activity in subcellular fractions of extracellular T. gondii tachyzoites. This indicates that IFN-γ directly affects parasite MAP kinase activity. The results provide evidence that MAP kinase pathways participate in the infection by T. gondii and that the decrease in MAP kinase activity in infected cells caused by IFN-γ may be involved in mediating their protective signals .     

Optimal Stimulation of the Left Ventricle

Optimal Stimulation of the Left Ventricle. Cardiac resynchronization therapy has been proposed to alleviate heart failure symptoms refractory to classic drug treatment. Potential benefits hinge on a number of key components, including judicious selection of patients likely to respond to the therapy and appropriate placement of the leads, particularly the lead responsible for left ventricular pacing. Evidence of ventricular asynchrony is an individual prerequisite for consideration of cardiac resynchronization therapy. Ventricular asynchrony can be diagnosed by recording a QRS duration > 150 msec or during echocardiography, with the goal of investigating the mechanical aspect of asynchrony. The optimal left ventricular pacing site can be defined by the latest segmental contraction, which is mainly the mid‐lateral wall. The first‐choice technique to initiate left ventricular pacing consists of a transvenous approach via the coronary sinus tributaries. In practice, the final left ventricular pacing location also depends on highly variant coronary sinus anatomy, acceptable electrical parameters, and lead stability. Procedure‐related complications, which consist mainly of coronary sinus perforation and phrenic nerve stimulation, remain low (<1%) and should decrease further with the use of new features specific to the procedure.     

Fractional Flow Reserve: The Ideal Parameter for Evaluation of Coronary, Myocardial, and Collateral Blood Flow by Pressure Measurements at PTCA

To overcome the fundamental limitations of coronary arteriography to assess the functional significance of coronary artery disease, it is necessary to obtain direct information about coronary blood flow. Recently we validated three pressure flow equations, which enable calculation of maximum coronary, myocardial, and collateral flow by merely measuring aortic, central venous, and distal coronary pressures under the condition of maximum vasodilation and using an ultra thin pressure monitoring guide wire for distal coronary pressure recording. In this paper, the first clinical experiences of this method are described. For that purpose, the concept of fractional flow reserve (FFR) is important. Fractional coronary flow reserve (FFR_cor) is defined as the maximum achievable blood flow in a stenotic artery, divided by normal maximum flow in that same artery, i.e. maximum flow in that artery in the case that it would be completely normal. Fractional myocardial flow reserve (FFR_myo) is defined in a similar way, and recruitable collateral blood flow is expressed as a fraction of normal maximum myocardial flow. Fractional flow reserve, defined in this way, is easy to obtain at percutaneous transluminal coronary angioplasty (PTCA) by the pressure-flow equations, is independent of pressure changes, applicable to three vessel disease, and enables calculation of the separate contribution of coronary and collateral flow to total myocardial perfusion. In 18 patients a very close correlation was demonstrated between FFR_myo, calculated by pressure recordings at PTCA by the first pressure flow equation, and FFR_myo obtained by positron emission tomography, which is considered the gold standard for myocardial perfusion. In 60 other patients, maximum recruitable collateral blood flow at balloon inflation (Q_c/Q^N) was calculated according to the third pressure-flow equation and correlated to the presence or absence of ischemia. It could be demonstrated that Q_C/Q^N exceeds 22% in all 23 patients without ischemia, whereas Q_c/Q^N was less than 22% in 34 out of 37 patients who experienced ischemia during balloon inflation. This margin value of 22% is very close to the theoretically expected value of 20%. based upon a coronary flow reserve of 5 under standard physiologic conditions. It can be concluded that the concept of fractional flow reserve provides a rapid, accurate, and elegant way for quantitative assessment of maximum coronary and myocardial blood flow before and after PTCA. Moreover, this is the first method that enables quantitative calculation of collateral blood flow in clinical practice. (J Interven Cardiol 1993; 6:331–344)     

Morphometric study of the equine navicular bone: variations with breeds and types of horse and influence of exercise

Navicular bones from the 4 limbs of 95 horses, classified in 9 categories, were studied. The anatomical bases were established for the morphometry of the navicular bone and its variations according to the category of horse, after corrections were made for front or rear limb, sex, weight, size and age. In ponies, navicular bone measurements were smallest for light ponies and regularly increased with body size, but in horses, navicular bone dimensions were smallest for the athletic halfbred, intermediate for draft horse, thoroughbreds and sedentary halfbreds and largest for heavy halfbreds. The athletic halfbred thus showed reduced bone dimensions when compared with other horse types. Navicular bones from 61 horses were studied histomorphometrically. Light horses and ponies possessed larger amounts of cancellous bone and less cortical bone. Draft horses and heavy ponies showed marked thickening of cortical bone with minimum intracortical porosity, and a decrease in marrow spaces associated with more trabecular bone. Two distinct zones were observed for the flexor surface cortex: an external zone composed mainly of poorly remodelled lamellar bone, disposed in a distoproximal oblique direction, and an internal zone composed mainly of secondary bone, with a lateromedial direction for haversian canals. Flexor cortex external zone tended to be smaller for heavy ponies than for the light ponies. It was the opposite for horses, with the largest amount of external zone registered for draft horses. In athletic horses, we observed an increase in the amount of cortical bone at the expense of cancellous bone which could be the result of reduced resorption and increased formation at the corticoendosteal junction. Cancellous bone was reduced for the athletic horses but the number of trabeculae and their specific surfaces were larger. Increased bone formation and reduced resorption could also account for these differences.     

Detoxification Mechanism in the Rat Extraorbital Lacrimal Gland: Conjugation of Brefeldin A to Glutathione

In this work the existence of a glutathione based detoxification system in rat lacrimal glands is reported. We showed that brefeldin A, a drug used as a tool for the study of intracellular trafficking mechanisms, was inactivated by metabolization and converted into two derivatives. We purified them by high performance liquid chromatography and determined, by mass spectroscopy, that they correspond to glutathione and cysteine derivatives of BFA. The determination of the respective amounts of these derivatives in the medium and the tissue in different experimental conditions, revealed that glutathione-BFA is formed in the tissue, excreted from the cells, cleaved by γ-glutamyl transpeptidase and finally converted to cysteine-BFA.