AMI in (bi)ventricular pacing - do not discard the ECG.

BACKGROUND: There is a growing number of patients with ventricular paced rhythm, who present to the emergency department with chest pain. The diagnosis of ST-segment elevation myocardial infarction (STEMI) and subsequent percutaneous coronary intervention (PCI) is often postponed, as the 12 leads-electrocardiogram (ECG) is discarded as not interpretable. There is a growing body of literature that suggests that Smith-modified Sgarbossa criteria can be applied for the diagnosis of STEMI in patients with paced rhythms. These criteria were originally developed for the interpretation of ECGs in patients with a left bundle branch block (LBBB) and chest pain, but have been expanded to paced ECGs. METHODOLOGY: We present three case reports with chest pain and right ventricular or biventricular pacing. FINDINGS: In all three cases, the Smith-modified Sgarbossa was positive and the diagnosis of STEMI could have been made early on. IMPLICATIONS: It remains important to look for ST-segment deviations and to compare the symptomatic ECG with previous asymptomatic ECGs. As the number of patients with potential acute myocardial infarction (AMI) and paced rhythms is likely to rise in the future, these criteria should be known to emergency physicians and cardiologists.

Effect of atmospheric pressure on sunflower (Helianthus annuus L.) protoplast division.

Sunflower protoplasts were cultured in liquid medium under high atmospheric pressure (0.2 to 0.6 MPa) and the plating efficiency, cell wall synthesis and microtubule organization were assessed. In 7-day-old cultures under a pressure of 0.4 MPa and above, the division rate was strongly reduced by more than 60% as compared to the control. Although most of the protoplasts had begun to regenerate a new cell wall they were unable to complete this process. Pressure also had an inhibitory effect on microtubule synthesis. The percentage of protoplasts showing a disassembled cortical network of microtubules was significantly increased up to 60% of the population. These effects were reversible: when protoplasts were transferred to normal pressure most of them rapidly recovered their capacity to divide and afterwards developed normally. Culturing protoplasts under a pressurized atmosphere revealed to be a good model system for studying cortical microtubule dynamics.

Effect of unbalanced diets on incorporation of delta-aminolevulinic acid into cytochrome P-450.

The in vivo syntheses of two liver microsomal cytochromes P-450 PB3a, P-450 UT50 [(1987) Eur. J. Biochem., submitted] (Mr 50,000, 52,000) have been estimated by measuring the specific activity 2 h after i.p. administration of delta-[3H]aminolevulinic acid to male Sprague Dawley rats. The animals were fed either a standard rat chow (5% lard, 22% casein) or unbalanced diets (high lipid, 30% lard or low protein, 6% casein) with or without 50 ppm Phenoclor DP6. The high-lipid diet supported a more rapid body weight gain but had little impact on cytochrome P-450 content, expressed either per whole liver or per mg microsomal protein, and on the incorporation of the precursor into cytochrome P-450. The latter was determined by measuring the radioactivity incorporated into the cytochrome P-450 fraction, partially purified by affinity chromatography, as well as into two cytochrome P-450 isozymes (Mr 50,000 or 52,000) purified by DEAE-52 cellulose ion-exchange chromatography. The low-protein diet, on the other hand, severely depressed body weight gain and cytochrome P-450 content as well as incorporation of radioactivity, the lower-Mr cytochrome (Mr 50,000) being particularly affected. However, when a potent inducer, Phenoclor DP6, was added to the low-protein diet, cytochrome synthesis was restored indicating that the effect was reversible.

Studies on the mechanism of nabam- and zineb-induced inhibition of the hepatic microsomal monooxygenases of the male rat.

In vitro effects of the ethylene bis-dithiocarbamate fungicides, nabam and zineb, on the hepatic microsomal monooxygenases of male rats were examined. Incubation of nabam and zineb with hepatic microsomes, without NADPH, leads to an inhibition of the metabolism of aminopyrine and aniline and to a denaturation of cytochrome P-450 into cytochrome P-420; in addition nabam causes the destruction of cytochrome P-450. Addition of NADPH into the incubation medium increases the inhibition of the monooxygenases, principally the inhibition of the metabolism of aniline induced by nabam. We studied the in vitro effects of three of the chief breakdown products of these fungicides: ethylene bis-isothiocyanate sulfide (EBIS), ethylene thiourea (ETU), and carbon disulfide (CS2). EBIS appears to be the only metabolite affecting directly (without NADPH) the hepatic monooxygenases activity. EBIS accounted partly for nabam-induced inhibition of the hepatic microsomal monooxygenases. The data suggest that the decrease of monooxygenases activity seen on incubation of nabam with hepatic microsomes may be due to the denaturation and destruction of cytochrome P-450 resulting from covalent binding of the compounds with cysteine sulfhydryl groups in cytochrome P-450. Inhibition of monooxygenase activity induced by zineb seems to be due to the reaction with the sulfhydryl groups of cytochrome P-450 and to another mechanism, probably related to its lipophilic character.

Lipid composition and monooxygenase relationship in liver microsomal membranes from rats fed unbalanced diets.

The cholesterol and phospholipid content of microsomal membrane from rats fed either a high lipid (H1) (30% lard) or a low protein (Lp) diet (6% casein) have been compared with those from rats fed a standard (St) diet (22% casein, 5% lard). For each diet, half of the group was treated with Phenochlor DP6. A significant increase in the phospholipid cholesterol ratio was observed in rats fed a high lipid diet or treated with DP6. These effects tend to increase the microsomal membrane fluidity. The protein deficiency decreased the phospholipid/cholesterol ratio and then the fluidity of the endoplasmic reticulum membrane. The specific activity of cytochrome P-450 to hydroxylate aniline which is independent to the enzymic form of cytochrome P-450 was closely correlated with the viscosity status of the microsomal membrane.