Selenium in the blood of patients with colorectal cancer and neoplastic polyp.

Samples of whole blood were obtained from 51 patients with newly diagnosed colorectal cancer as well as from 76 patients with neoplastic colorectal polyp, and from 30 healthy blood bank donors. Selenium was determined by the fluorimetric method. Significantly decreased selenium concentrations of blood samples from patients with colorectal cancer and villous adenoma were found. There was not any correlation between the blood selenium levels of patients with adenomatous polyp and the severity of dysplasia in removed polyps. The lowest mean selenium level in patients with villous adenoma indicates that selenium deficiency may be an important factor in the development of colorectal cancer arising from villous adenomas.     

Electron transport across the plasmalemma of Lemna gibba G1

Lemna gibba L., grown in the presence or absence of Fe, reduced extracellular ferricyanide with a V _max of 3.09 mol · g^-1 fresh weight · h^-1 and a K _m of 115 M. However, Fe³⁺-ethylenediaminetetraacetic acid (EDTA) was reduced only after Fe-starvation. External electron acceptors such as ferricyanide, Fe³⁺-EDTA, 2,6-dichlorophenol indophenol or methylene blue induced a membrane depolarization of up to 100 mV, but electron donors such as ferrocyanide or NADH had no effect. Light or glucose enhanced ferricyanide reduction while the concomitant membrane depolarization was much smaller. Under anaerobic conditions, ferricyanide had no effect on electrical membrane potential difference (E_m). Ferricyanide reduction induced H⁺ and K⁺ release in a ratio of 1.16 H⁺+1 K⁺/2 e^- (in +Fe plants) and 1.28 H⁺+0.8 K⁺/2 e^- (in -Fe plants). Anion uptake was inhibited by ferricyanide reduction. It is concluded that the steady-state transfer of electrons and protons proceeds by separate mechanisms, by a redox system and by a H⁺-ATPase.Abbreviations E _m electrical membrane potential difference - EDTA ethylenediaminetetraacetic acid - DCPIP dichlorophenol indophenol - +Fe control plant - -Fe iron-deficient plant - FW fresh weight - H⁺ electrochemical proton gradient     

Monoclonal antibodies modify acetylcholine-induced ionic channel properties in cultured chick myoballs

Summary Monoclonal antibodies directed against the cholinergic binding site of the acetylcholine receptor were found to alter the ion channel properties in cultured chick myoballs. Time and dose dependent reduction in acetylcholine sensitivity was observed. Noise analysis experiments indicated a decrease in the mean single channel conductance and an increase in the mean single channel open time.     

Evidence for proton/sulfate cotransport and its kinetics inLemna gibba G1

Sulfate uptake into duckweed (Lemna gibba G1) was studied by means of [³⁵S]sulfate influx and measurements of electrical membrane potential. Uptake was strongly regulated by the intracellular content of soluble sulfate. At the onset of sulfate uptake the membrane potential was transiently depolarized. Fusicoccin stimulated uptake up to 165% of the control even at pH 8. It is suggested that sulfate uptake is energized in the whole pH range by a 3H⁺/sulfate cotransport mechanism. Kinetics of sulfate uptake and sulfate-induced membrane depolarization in the concentration range of 5 M to 1 mM sulfate at pH 5.7 was best described by two Michaelis-Menten terms without any linear component. The second system had a lower affinity for sulfate and was fully active only at sufficiently high proton concentrations.Abbreviations c _o extracellular sulfate concentration - c _i intracellular sulfate concentration - E _m electrical membrane potential difference - E _m sulfate-induced, maximal membrane depolarization - electrochemical proton gradient - FW fresh weight     

Altered sensitivity to colchicine and PHA in human cultured cells

Summary PHA-stimulated lymphocytes cultivated from a pair of human monozygotic twins yielded mostly tetraploid cells when colchicine was not used to arrest the metaphases. The rate of tetraploidy was also enhanced by colchicine in fibroblasts cultured without PHA. In in situ condition, larger than usual cells were observed. Other defects found in parental lymphocyte cultures included C-anaphase cells and increased cell aggregation. These results suggest a membrane mutation resulting in hypersensitivity to PHA and variant response to colchicine.     

Cardiac-specific overexpression of perilipin 5 provokes severe cardiac steatosis via the formation of a lipolytic barrier

Cardiac triacylglycerol (TG) catabolism critically depends on the TG hydrolytic activity of adipose triglyceride lipase (ATGL). Perilipin 5 (Plin5) is expressed in cardiac muscle (CM) and has been shown to interact with ATGL and its coactivator comparative gene identification-58 (CGI-58). Furthermore, ectopic Plin5 expression increases cellular TG content and Plin5-deficient mice exhibit reduced cardiac TG levels. In this study we show that mice with cardiac muscle-specific overexpression of perilipin 5 (CM-Plin5) massively accumulate TG in CM, which is accompanied by moderately reduced fatty acid (FA) oxidizing gene expression levels. Cardiac lipid droplet (LD) preparations from CM of CM-Plin5 mice showed reduced ATGL- and hormone-sensitive lipase-mediated TG mobilization implying that Plin5 overexpression restricts cardiac lipolysis via the formation of a lipolytic barrier. To test this hypothesis, we analyzed TG hydrolytic activities in preparations of Plin5-, ATGL-, and CGI-58-transfected cells. In vitro ATGL-mediated TG hydrolysis of an artificial micellar TG substrate was not inhibited by the presence of Plin5, whereas Plin5-coated LDs were resistant toward ATGL-mediated TG catabolism. These findings strongly suggest that Plin5 functions as a lipolytic barrier to protect the cardiac TG pool from uncontrolled TG mobilization and the excessive release of free FAs.     

Vascular NAD(P)H oxidases: specific features,expression, and regulation

The importance of reactive oxygen species (ROS) in vascular physiology and pathology is becoming increasingly evident. All cell types in the vascular wall produce ROS derived from superoxide-generating protein complexes similar to the leukocyte NADPH oxidase. Specific features of the vascular enzymes include constitutive and inducible activities, substrate specificity, and intracellular superoxide production. Most phagocyte enzyme subunits are found in vascular cells, including the catalytic gp91phox (aka, nox2), which was the earliest member of the newly discovered nox family. However, smooth muscle frequently expresses nox1 rather than gp91phox, and nox4 is additionally present in all cell types. In cell culture, agonists increase ROS production by activating multiple signals, including protein kinase C and Rac, and by upregulating oxidase subunits. The oxidases are also upregulated in vascular disease and are involved in the development of atherosclerosis and a significant part of angiotensin II-induced hypertension, possibly via nox1 and nox4. Likewise, enhanced vascular oxidase activity is associated with diabetes. Therefore, members of this enzyme family appear to be important in vascular biology and disease and constitute promising targets for future therapeutic interventions.     

ATGL and CGI-58 are lipid droplet proteins of the hepatic stellate cell line HSC-T6

Lipid droplets (LDs) of hepatic stellate cells (HSCs) contain large amounts of vitamin A [in the form of retinyl esters (REs)] as well as other neutral lipids such as TGs. During times of insufficient vitamin A availability, RE stores are mobilized to ensure a constant supply to the body. To date, little is known about the enzymes responsible for the hydrolysis of neutral lipid esters, in particular of REs, in HSCs. In this study, we aimed to identify LD-associated neutral lipid hydrolases by a proteomic approach using the rat stellate cell line HSC-T6. First, we loaded cells with retinol and FAs to promote lipid synthesis and deposition within LDs. Then, LDs were isolated and lipid composition and the LD proteome were analyzed. Among other proteins, we found perilipin 2, adipose TG lipase (ATGL), and comparative gene identification-58 (CGI-58), known and established LD proteins. Bioinformatic search of the LD proteome for α/β-hydrolase fold-containing proteins revealed no yet uncharacterized neutral lipid hydrolases. In in vitro activity assays, we show that rat (r)ATGL, coactivated by rat (r)CGI-58, efficiently hydrolyzes TGs and REs. These findings suggest that rATGL and rCGI-58 are LD-resident proteins in HSCs and participate in the mobilization of both REs and TGs.