Biochemical and Ultrastructural Changes in Wheat Plants during Drought Stress.

Drought severely slows down plant growth, decreases crop yield, and affects various physiological processes in plants. We examined four local bread wheat cultivars with different drought tolerance (drought-tolerant Zirva 85 and Murov 2 and drought-sensitive Aran and Gyzyl bughda cultivars). Leaves from seedlings of drought-tolerant plants demonstrated higher activity of antioxidant enzymes and lower levels of malondialdehyde and hydrogen peroxide. The content of soluble proteins in drought-exposed increased, possibly due to the stress-induced activation of gene expression and protein synthesis. Drought-exposed Zirva 85 plants exhibited an elevated activity of nitrogen and carbon metabolism enzymes. Ultrastructural analysis by transmission electron microscopy showed drought-induced damage to mesophyll cells and chloroplast membranes, although it was manifested less in the drought-tolerant cultivars. Comparative analysis of the activity of metabolic and antioxidant enzymes, as well as observed ultrastructural changes in drought-exposed plants revealed that the response to drought of seedlings was more pronounced in drought-tolerant cultivars. These findings can be used in further studies of drought stress in wheat plants under natural conditions.

Exposure of rainbow trout (Oncorhynchus mykiss) to magnetite (Fe3O4) nanoparticles in simplified food chain: Study on ultrastructural characterization.

The widespread exposure of metallic nanoparticles to the aquatic ecosystem and its adverse impact on human life is the colossal concern worldwide. In view of this, this context was investigated to analyze microscopically the bioaccumulation and localization of magnetite (Fe3O4) nanoparticles in the cellular organelles of rainbow trout (Oncorhynchus mykiss, Walbaum, 1792) in aquatic conditions. Initially, Fe3O4 nanoparticles were absorbed on to Elodea (Elodea canadensis) and fed to molluscs (Melanopsis praemorsa). Fish were fed with the same molluscs, and then the intestines and liver were examined using light and transmission electron microscopy. Results showed that nanoparticles were present in the cytoplasm and other organelles of cells (mitochondrion and lysosome) by absorbing through microvilli of the epithelial cells of the tunica mucosa in the intestine. Further, nanoparticles passed through the vessels of the lamina propria of the tunica mucosa and reached to the sinusoids of the liver via blood circulation. It was then accumulated from the endothelium of the sinusoid to the cytoplasm of liver hepatocytes and to mitochondria and lysosome. The accumulation of nanoparticles in the epithelial cells, cytoplasm, mitochondria, and lysosome revealed the degree of transparency of the pattern with slight hesitation. In summary, this investigation contributed towards the understanding of the physiological effects of Fe3O4 nanoparticles on O. mykiss, which ascertains essentiality for sustainable development of nanobiotechnology in the aquatic ecosystem.

Biochemical properties and ultrastructure of mesophyll and bundle sheath thylakoids from maize (Zea mays) chloroplasts.

A characteristic feature of C4 plants is the differentiation of the photosynthetic leaf tissues into two distinct cell types: mesophyll (M) and bundle sheath (BS) cells. We have investigated several biochemical parameters, including pigment composition, polypeptide patterns, fluorescence at 77K, the activity of photosystems and ultrastructure of mesophyll and bundle sheath chloroplasts of maize (Zea mays L.) plants. It is shown that the BS chloroplasts have ~2-fold higher chlorophyll a/b ratio than M chloroplasts, 6.15 and 3.12 respectively. The PSI apoprotein (68 kDa) was more abundant in BS than in M thylakoids. Polypeptides belonging to PSII core antenna, are in similar amounts in both types of membranes, but the 45kDa band is more intensive in M thylakoids. Polypeptides in the region of 28-24 kDa of the light-harvesting complex of PSII (LHCII) are also present in both types of chloroplasts, though their amounts are reduced in BS thylakoids. The chlorophyll fluorescence emission spectra in M cells showed the presence of three bands at 686, 695 and 735 nm characteristics of LHCII, PSII core and PSI complexes, respectively. However, in the fluorescence spectrum of agranal plastids, there are almost traces of the band at 695 nm, which belongs to the PSII core complex. The research results revealed that the photochemical activity of PSII in BS chloroplasts is ~5 times less than in the chloroplasts of M cells. The highest PSI activity was found in maize BS chloroplasts.

The role of oxidative stress in the pathophysiology of cerebrovascular lesions in Alzheimer's disease.

Alzheimer's disease (AD) and stroke are two leading causes of age-associated dementia. A rapidly growing body of evidence indicates that increased oxidative stress from reactive oxygen radicals is associated with the aging process and age-related degenerative disorders such as atherosclerosis, ischemia/reperfusion, arthritis, stroke, and neurodegenerative diseases. New evidence has also indicated that vascular lesions are a key factor in the development of AD. This idea is based on a positive correlation between AD and cardiovascular and cerebrovascular diseases such as arterio- and atherosclerosis and ischemia/reperfusion injury. In this review we consider recent evidence supporting the existence of an intimate relationship between oxidative stress and vascular lesions in the pathobiology of AD. We also consider the opportunities for therapeutic interventions based on the molecular pathways involved with these causal relationships.