The localization of calcium by X-ray microanalysis in myopathic muscle fibers

An electron histochemical study was undertaken to localize calcium with ammonium oxalate precipitation technique in soleus muscle of rat in normal cases and in myopathy induced experimentally by a prolonged treatment of 2,4-dichlorophenoxyacetate (2,4-D). The calcium content of precipitates was detected by energy-dispersive X-ray microanalysis. In normal cases, the electron dense precipitates containing calcium were mainly found in the vesicles of sarcoplasmic reticulum, whereas in 2,4-D induced myopathy the deposits were shifted near the Z line into the myofibrils. Calcium, because the uptake into sarcoplasmic vesicles was inhibited by 2,4-D, could attach to other binding sites, such as to the troponin-C.A long-lasting binding of calcium might lead to a prolonged activation of the actin-myosin system.     

Affi-gel blue treatment simplifies the protein composition of sarcoplasmic reticulum vesicles

Sarcoplasmic reticulum vesicles isolated by conventional techniques usually contain, in addition to the recognized sarcoplasmic reticulum components, several other proteins (phosphorylase, myosin, glyceraldehyde-3-phosphate dehydrogenase, etc.) in variable amounts; these proteins complicate the interpretation of chemical modification data. Incubation of sarcoplasmic reticulum vesicles with Affi-Gel blue particles for 1-4 h at 2 degrees C, followed by sedimentation of the Affi-Gel in a clinical centrifuge, simplifies the protein composition by selective adsorption of the accessory proteins, and improves the consistency of the preparations. The Affi-Gel blue treatment is recommended as part of the standard procedure for the isolation of sarcoplasmic reticulum vesicles.     

Quercetin and genistein hindering effect of neomycin action in the liverwort <Emphasis Type="Italic">Conocephalum conicum</Emphasis>

Apigenin, quercetin and genistein are members of the family of plant flavonoids suspected to prevent a number of human diseases, for instance cancer development. They display a number of activities, and part of their beneficial effects may be due to their affinity to cellular membranes. In this study, we used Conocephalum conicum, a well-elaborated model of liverworts. Intracellular microelectrode measurements were carried out to examine the effects of flavonoids in combination with neomycin on the resting and action potentials. Neomycin triggered gradual decline of action potential amplitudes through a membrane potential decrease (membrane potential became less negative) and a decrease of the action potential peak value. Additionally, duration of action potential amplitudes measured at half of the amplitude increased in neomycin-treated plants. However, the simultaneous use of quercetin or genistein (but not apigenin) with neomycin hindered neomycin-specific actions. Hence, the membrane resting potential and action potential amplitudes regained neomycin-free values. It may be concluded that application of at least some flavonoids (namely quercetin and genistein) exerts strong influence on electrical membrane responses in C. conicum.     

Leaf features of silver birch (Betula pendula Roth). Variability within and between two populations (uncontaminated vs Pb-contaminated and Zn-contaminated site)

Fourteen morphometric variables of silver birch (Betula pendula Roth) leaves from two sites in the Upper Silesia province were analyzed to establish the pattern of intrapopulational and interpopulational relations. The leaves were collected from ten trees growing on a zinc–lead dump as well as from ten trees in the unpolluted area of Mirów within the same bioclimatic region. Leaf samples were collected from the trees during the vegetative seasons 1999 and 2000. The size and shape of leaves were studied using standard biometric methods. Cluster analysis indicated overall differences between the populations. Both populations differed with respect to almost all the morphometric variables (P<0.05). Most variables of the leaves, collected from single trees (or combined as a total) on the zinc–lead dump showed more variability than those from the unpolluted site. Discriminant function analysis confirmed the angle of the leaf base as the most important variable in the evaluation of interpopulational variability of leaves.     

Heavy metal-induced oxidative damage, defense reactions, and detoxification mechanisms in plants

Heavy metal (HMs) contamination is widespread globally due to anthropogenic, technogenic, and geogenic activities. The HMs exposure could lead to multiple toxic effects in plants by inducing reactive oxygen species (ROS), which inhibit most cellular processes at various levels of metabolism. ROS being highly unstable could play dual role (1) damaging cellular components and (2) act as an important secondary messenger for inducing plant defense system. Cells are equipped with enzymatic and non-enzymatic defense mechanisms to counteract this damage. Some are constitutive and others that are activated only when a stress-specific signal is perceived. Enzymatic scavengers of ROS include superoxide dismutase, catalase, glutathione reductase, and peroxidase, while non-enzymatic antioxidants are glutathione, ascorbic acid, α-tocopherol, flavonoids, anthocyanins, carotenoids, and organic acids. The intracellular and extracellular chelation mechanisms of HMs are associated with organic acids such as citric, malic and oxalic acid, etc. The important mechanism of detoxification includes metal complexation with glutathione, amino acids, synthesis of phytochelatins and sequestration into the vacuoles. Excessive stresses induce a cascade, MAPK (mitogen-activated protein kinase) pathway and synthesis of metal-detoxifying ligands. Metal detoxification through MAPK cascade and synthesis of metal-detoxifying ligands will be of considerable interest in the field of plant biotechnology. Further, the photoprotective roles of pigments of xanthophylls cycle under HMs stress were also discussed.