Studies of energy conservation in Chlamydomonas reinhardii

An attempt was made to gain an insight into the energy conservation process in Chlamydomonas reinhardii. This organism possesses both mitochondria and a chloroplast and so respiration and photosynthesis can be studied in the same cell. The growth of C.reinhardii under different trophic conditions was characterised. The sensitivity of the wild-type (wt+) strain to a wide range, of inhibitors was determined in order to select potentially useful inhibitors for the isolation of drug-resistant mutants. The effect of these inhibitors on energy conservation was determined using chloroplast preparations from pea (Pisum sativum) and the CW15+ (cell wall-1ess) strain of C.reinhardii. The reported modes of action of the triorganotins and alky1guanidines on photosynthetic energy conservation were confirmed and, in some cases, extended. Mutant strains of C.reinhardii, which are resistant to inhibitors of oxidativa and photosynthetic phosphorylation, may provide an insight into the energy conservation process. Drug-resistant strains ot C.reinhardii were isolated and divided into five major classes on the basis of their cross-resistance characteristics. The TP-8+ (triorganotin-resistant) mutant was specifically resistant to trimethy1tin and triethy1tin but more sensitive than the Wt+ strain to other inhibitors. The alkylguanidine and ethidium bromide-resistant mutants exhibited pleiotropic resistance patterns to other membrane-active inhibitors. The resistance phenotypes of all the mutant strains were inherited in a Mendelian fashion and were generally present under different trophic conditions. The resistance, in these mutants may be due to change(s) in one or more of the cell membranes but the exact locus of resistance was not, determined. However, the resistance of the EBr-6+ (ethidium bromide-resistant) strain may be due to reduced uptake of ethidium bromide. Attempts to localise the mode of resistance of the TP-8+ strain at the sub-cellular level were unsuccessful

The yield of head CT in syncope: a pilot study

Although head CT is often routinely performed in emergency department (ED) patients with syncope, few studies have assessed its value

Myocardial ultrasonic tissue characterization in patients with thyroid dysfunction

<p>Abstract</p> <p>Background</p> <p>Structural myocardial abnormalities have been extensively documented in hypothyroidism. Experimental studies in animal models have also shown involvement of thyroid hormones in gene expression of myocardial collagen. This study was planned to investigate the ability of ultrasonic tissue characterization, as evaluated by integrated backscatter (IBS), to early identify myocardial involvement in thyroid dysfunction.</p> <p>Patients and Methods</p> <p>We studied 15 patients with hyperthyroidism (HYPER), 8 patients with hypothyroidism (HYPO), 14 patients with subclinical hypothyroidism (SCH) and 19 normal (N) subjects, who had normal LV systolic function. After treatment, 10 HYPER, 6 HYPO, and 8 SCH patients were reevaluated. IBS images were obtained and analyzed in parasternal short axis (papillary muscle level) view, at left ventricular (LV) posterior wall. The following IBS variables were analyzed: 1) the corrected coefficient (CC) of IBS, obtained by dividing IBS intensity by IBS intensity measured in a rubber phantom, using the same equipment adjustments, at the same depth; 2) cardiac cyclic variation (CV) of IBS - peak-to-peak difference between maximal and minimal values of IBS during cardiac cycle; 3) cardiac cyclic variation index (CVI) of IBS - percentual relationship between the cyclic variation (CV) and the mean value of IBS intensity.</p> <p>Results</p> <p>CC of IBS was significantly larger (p < 0.05) in HYPER (1.57 ± 0.6) and HYPO (1.53 ± 0.3) as compared to SCH (1.32 ± 0.3) or N (1.15 ± 0.27). The CV (dB) (HYPO: 7.5 ± 2.4; SCH: 8.2 ± 3.1; HYPER: 8.2 ± 2.0) and the CVI (HYPO: 35.6 ± 19.7%; SCH: 34.7 ± 17.5%; HYPER: 37.8 ± 11.6%) were not significantly different in patients with thyroid dysfunction as compared to N (7.0 ± 2.0 and 44.5 ± 15.1%).</p> <p>Conclusions</p> <p>CC of IBS was able to differentiate cardiac involvement in patients with overt HYPO and HYPER who had normal LV systolic function. These early myocardial structural abnormalities were partially reversed by drug therapy in HYPER group. On the other hand, although mean IBS intensity tended to be slightly larger in patients with SCH as compared to N, this difference was not statistical significant.</p

Myocardial Structural Alteration and Systolic Dysfunction in Preclinical Hypertrophic Cardiomyopathy Mutation Carriers

BACKGROUND: To evaluate the presence of myocardial structural alterations and subtle myocardial dysfunction during familial screening in asymptomatic mutation carriers without hypertrophic cardiomyopathy (HCM) phenotype. METHODS AND FINDINGS: Sixteen HCM families with pathogenic mutation were studied and 46 patients with phenotype expression (Mut+/Phen+) and 47 patients without phenotype expression (Mut+/Phen-) were observed. Twenty-five control subjects, matched with the Mut+/Phen- group, were recruited for comparison. Echocardiography was performed to evaluate conventional parameters, myocardial structural alteration by calibrated integrated backscatter (cIBS) and global and segmental longitudinal strain by speckle tracking analysis. All 3 groups had similar left ventricular dimensions and ejection fraction. Basal anteroseptal cIBS was the highest in Mut+/Phen+ patients (-14.0+/-4.6 dB, p-19.0 dB basal anteroseptal cIBS or >-18.0% basal anteroseptal longitudinal strain had a sensitivity of 98% and a specificity of 72% in differentiating Mut+/Phen- group from controls. CONCLUSION: The use of cIBS and segmental longitudinal strain can differentiate HCM Mut+/Phen- patients from controls with important clinical implications for the family screening and follow-up of these patients.published_or_final_versio