18 research outputs found
Effects of juglone and lawsone on oxidative stress in maize coleoptile cells treated with IAA
Naphthoquinones are secondary metabolites widely distributed in nature and produced by bacteria, fungi and higher plants. Their biological activity may result from induction of oxidative stress, caused by redox cycling or direct interaction with cellular macromolecules, in which quinones act as electrophiles. The redox homeostasis is known as one of factors involved in auxin-mediated plant growth regulation. To date, however, little is known about the crosstalk between reactive oxygen species (ROS) produced by quinones and the plant growth hormone auxin (IAA). In this study, redox cycling properties of two naphthoquinones, juglone (5-hydroxy-1,4-naphthoquinone) and lawsone (2-hydroxy-1,4-naphthoquinone), were compared in experiments performed on maize coleoptile segments incubated with or without the addition of IAA. It was found that lawsone was much more effective than juglone in increasing both H2O2 production and the activity of antioxidative enzymes (SOD, POX and CAT) in coleoptile cells, regardless of the presence of IAA. An increase in the activity of Cu/Zn-SOD isoenzymes induced by both naphthoquinones suggests that juglone- and lawsone-generated H2O2 was primarily produced in the cytosolic and cell wall spaces. The cell potential to neutralize hydrogen peroxide, determined by POX and CAT activity, pointed to activity of catalase as the main enzymatic mechanism responsible for degradation of H2O2. Therefore, we assumed that generation of H2O2, induced more efficiently by LW than JG, was the major factor accounting for differences in the toxicity of naphthoquinones in maize coleoptiles. The role of auxin in the process appeared negligible. Moreover, the results suggested that oxidative stress imposed by JG and LW was one of mechanisms of allelopathic action of the studied quinones in plants
Mature Luffa Leaves (Luffa cylindrica L.) as a Tool for Gene Expression Analysis by Agroinfiltration
Ultrastructure of the ventromedial hypothalamic nucleus in fasted and refed young and old rats
Many hypothalamic nuclei are involved in the regulation of food intake and
energy homeostasis. An ultrastructural investigation of the hypothalamic ventromedial nucleus (VMN), a hypothetical "satiety centre" was performed to explore the morphological basis of altered feeding behaviour of old rats in an experimental model of fasting/refeeding. Young (5 months old, n = 12) and old (24 months old, n = 12) male Wistar rats were fasted for 48 hours, then refed for 24 hours and sampled thereafter. Brain tissue was fixed by perfusion, histological
and ultrathin sections were obtained by routine methods. Although food
intake was similar in control young and old rats, during refeeding old animals consumed less chow than young ones. The EM analysis of VMN neurones of old control rats revealed, besides typical age-related residual bodies, deep indentations of the nuclear envelope and the presence of long, undulating rough endoplasmic
reticulum cisternae in the cell periphery. In both young and old rats
fasting for 48 hours led to the expansion of Golgi complexes and increased folds of the nuclear envelope, which is suggestive of enhanced cellular activity of the
VMN neurones. These fasting-induced alterations were sustained in the VMN
neurones of refed rats in both age groups. The results showed that the VMN
neurones of old control rats differ at the ultrastructural level from young ones. However, starvation and subsequent refeeding cause similar alterations in the hypothalamic neurones of "satiety centre" of both young and old rats
The effect of fasting and refeeding on the ultrastructure of the hypothalamic paraventricular nucleus in young and old rats
In order to explore the morphological basis of the altered feeding behaviour of
old rats, an ultrastructural investigation of the magnocellular neurons of the
hypothalamic paraventricular nucleus (PVN) was performed. Young and old male
Wistar rats, 5 and 24 months old, respectively, and with each age group comprising
12 animals, were divided into 3 groups. The rats in Group I were used as
controls (normally fed), the rats of Group II were fasted for 48 hours and in
Group III the rats were fasted for 48 hours and then refed for 24 hours. The
brains were fixed by perfusion and histological and ultrathin sections were obtained
by routine methods. Common features of the magnocellular PVN neurons
of young and old rats were abundant Golgi complexes and short fragments
of RER localised at the cell periphery. In contrast to young rats, the PVN neurons
of old animals showed deep indentations of the nuclear envelope and agerelated
residual bodies. In both age groups fasting for 48 hours led to the expansion
of the Golgi complexes and dilatation of RER cisternae. In contrast to
those in fed rats, RER cisternae in the neurons of old fasted animals were situated
between the nuclear envelope and the Golgi zone. Prolonged RER cisternae
were distributed in the peripheral cytoplasm of refed old rats. Our observations
suggest that at the ultrastructural level the process of ageing does not change
the responsiveness of magnocellular PVN neurons to fasting-refeeding
Time- and Dose-Dependent Induction of HSP70 in Lemna minor Exposed to Different Environmental Stressors
The objective of this study was to examine the influence of different stressors, including cadmium (heavy metal), anthracene (polycyclic aromatic hydrocarbon—PAH) and chloridazon (herbicide), on population growth and biosynthesis of cytoplasmic HSP70 in Lemna minor (duckweed) in short (4 h)- and long (7 days)-term tests. A heat shock response was confirmed in Lemna exposed to high temperature: 35, 37.5, 40, or 42.5°C in short-term (4 h) treatments. The chemicals tested stimulated the biosynthesis of the cytoplasmic HSP70 protein in a concentration-dependent way (0.5–5 μM), higher in fronds exposed to lower doses of stressors. Additionally, production of HSP70 was greater after 4 h of incubation than after 7 days. The results suggest that HSP70 could be applied as a non-specific and sensitive detector of stress induced by different chemicals at concentrations below those that produce the type of response observed in classical cytotoxicity tests, such as growth inhibition
Sensitivity to fuel diesel oil and cell wall structure of some Scenedesmus (Chlorococcales) strains
Sensitivity of three Scenedesmus strains exposed to aqueous fuel-oil extract (AFOE) is strongly strain-dependent S. quadricauda is the most resistant, S. armatus moderately tolerant whereas the most sensitive appears to be S. microspina. The sensitivity of tested species increases parallel with decreasing of cell size and cell number in coenobium. The values of the cell surface/cell volumes ratios only partly explain the above relationships. Electron microscope investigations reveal that the sensitivity may depend on cell wall structure of the strains. Cell wall of all here investigated strains is built of two layers: the inner so-called cellulosic layer and the outer one showing a three-laminar structure (TLS). The latter contains an acetolysis-resistant biopolymer (ARB). These two layers are similar in thickness in the three strains tested, but the surface of Scenedesmus is covered with various epistructures that are characteristic of strains. Some of them as the tightly fitting warty layer of S. armatus and especially the loosely fitting reticulate layer of S. quadricauda may contribute to lower permeability of cell wall. The structure of the rosettes also appears to be correlated with the sensitivity of strains. Presence of invaginations of plasmalemma in areas under rosettes indicates their role in transport processes inside/outside the cells
Chlamydomonas reinhardtii — a model organism in research of cell, mitochondrial and chloroplast cycle
Względna łatwość hodowli, krótki cykl komórkowy, znana sekwencja genomu, a także duża ilość różnego rodzaju mutantów czynią z Chlamydomonas reinhardtii atrakcyjny organizm modelowy w badaniach dotyczących rozwoju i funkcjonowania komórki. Struktura genomu jądrowego i chloroplastowego C. reinhardtii wykazuje więcej cech wspólnych z genomami roślin wyższych niż prostych eukariontów. Genom mitochondrialny tego organizmu jest jednym z najmniejszych dotychczas poznanych u roślin i występuje w postaci liniowej, dwuniciowej cząsteczki. Zsekwencjonowanie gnomów Chlamydomonas reinhardtii oraz możliwość ich względnie łatwej transformacji stwarza dogodne podstawy do badania molekularnych uwarunkowań przebiegu cyklu komórkowego i zależności pomiędzy cyklem komórkowym, chloroplastowym i mitochondrialnym.The relative ease of culture, a short cell cycle, known whole genome sequence and a large number of different types of Chlamydomonas reinhardtii mutants, make this unicellular green alga a very attractive model organism for studies of the development and functioning of cell.The structure of nuclear and chloroplast genome of C. reinhardtii is more resembling genomes of vascularplants than simple eukaryotes. Mitochondrial genome of this organism is one of the smallest in plants and occurs as a linear, double-stranded molecule. Known whole genome sequence and the possibility of their transformation have allowed Chlamydomonas reinhardtii to become a highly valuable model for molecular approaches of cell cycle regulation and relationship between the cell, mitochondrial and chloroplast cycle
Effects of juglone and lawsone on oxidative stress in maize coleoptile cells treated with IAA
Naphthoquinones are secondary metabolites widely distributed in nature and produced by bacteria, fungi and higher plants. Their biological activity may result from induction of oxidative stress, caused by redox cycling or direct interaction with cellular macromolecules, in which quinones act as electrophiles. The redox homeostasis is known as one of factors involved in auxin-mediated plant growth regulation. To date, however, little is known about the crosstalk between reactive oxygen species (ROS) produced by quinones and the plant growth hormone auxin (IAA). In this study, redox cycling properties of two naphthoquinones, juglone (5-hydroxy-1,4-naphthoquinone) and lawsone (2-hydroxy-1,4-naphthoquinone), were compared in experiments performed on maize coleoptile segments incubated with or without the addition of IAA. It was found that lawsone was much more effective than juglone in increasing both H2O2 production and the activity of antioxidative enzymes (SOD, POX and CAT) in coleoptile cells, regardless of the presence of IAA. An increase in the activity of Cu/Zn-SOD isoenzymes induced by both naphthoquinones suggests that juglone- and lawsone-generated H2O2 was primarily produced in the cytosolic and cell wall spaces. The cell potential to neutralize hydrogen peroxide, determined by POX and CAT activity, pointed to activity of catalase as the main enzymatic mechanism responsible for degradation of H2O2. Therefore, we assumed that generation of H2O2, induced more efficiently by LW than JG, was the major factor accounting for differences in the toxicity of naphthoquinones in maize coleoptiles. The role of auxin in the process appeared negligible. Moreover, the results suggested that oxidative stress imposed by JG and LW was one of mechanisms of allelopathic action of the studied quinones in plants