Manganese activates the mitochondrial apoptotic pathway in rat astrocytes by modulating the expression of proteins of the Bcl-2 family

Manganese induces the central nervous system injury leading to manganism, by mechanisms not completely understood. Chronic exposure to manganese generates oxidative stress and induces the mitochondrial permeability transition. In the present study, we characterized apoptotic cell death mechanisms associated with manganese toxicity in rat cortical astrocytes and demonstrated that (i) Mn treatment targets the mitochondria and induces mitochondrial membrane depolarization followed by cytochrome c release to the cytoplasm, (ii) Mn induces both effector caspases 3/7 and 6 as well as PARP-1 cleavage and (iii) Mn shifts the balance of cell death/survival of Bcl-2 family proteins to favor the apoptotic demise of astrocytes. Our model system using cortical rat astrocytes treated with Mn would emerge as a good tool for investigations aimed to elucidate the role of apoptosis in manganism.     

Effects of silkworm larvae powder containing manganese superoxide dismutase on immune activity of mice

To study the function of silkworm larvae powder containing superoxide dismutase and potential practical development, we investigated the safety assessment and effects on immune activity of mice such as the growth of immunity-related organs, delayed-type hypersensitivity (DTH) and charcoal particle clearance ability. The mean body weights in treated mice were significantly heavier than that of control, meanwhile, the ratio of splenocytes/body weight and the thoracic gland/body weight in treated mice was significantly enhanced after 30 days treated with silkworm larvae powder containing manganese superoxide dismutase. The treated mice resulted in a profound activation of the DTH and charcoal particle clearance, and indicated the treated mice have stronger phagocytic activity to exogenous materials. Our data also indicated the feeding treatment was safe with 360 folds of recommended human dosage in acute toxic test. In long-term test, there were no effects of silkworm larvae powder containing SOD on treated mice’s growth and inside organs as long as 90 days. Further the electronic microscope investigation showed the intestine, liver, splenocyte and stomach in mice were no obvious changes both in organs and sub-organs such as nucleus, endoplasmic reticulum, mitochondrion, Golgi and peroxisomes after treated for as long as 90 days.     

The influence of the ectomycorrhizal fungus Rhizopogon subareolatus on growth and nutrient element localisation in two varieties of Douglas fir (Pseudotsuga menziesii var. menziesii and var. glauca) in response to manganese stress

Acidification of forest ecosystems leads to increased plant availability of the micronutrient manganese (Mn), which is toxic when taken up in excess. To investigate whether ectomycorrhizas protect against excessive Mn by improving plant growth and nutrition or by retention of excess Mn in the hyphal mantle, seedlings of two populations of Douglas fir (Pseudotsuga menziesii), two varieties, one being menziesii (DFM) and the other being glauca (DFG), were inoculated with the ectomycorrhizal fungus Rhizopogon subareolatus in sand cultures. Five months after inoculation, half of the inoculated and non-inoculated seedlings were exposed to excess Mn in the nutrient solution for further 5 months. At the end of this period, plant productivity, nutrient concentrations, Mn uptake and subcellular compartmentalisation were evaluated. Non-inoculated, non-stressed DFM plants produced about 2.5 times more biomass than similarly treated DFG. Excess Mn in the nutrient solution led to high accumulation of Mn in needles and roots but only to marginal loss in biomass. Colonisation with R. subareolatus slightly suppressed DFM growth but strongly reduced that of DFG (-50%) despite positive effects of mycorrhizas on plant phosphorus nutrition. Growth reductions of inoculated Douglas fir seedlings were unexpected since the degree of mycorrhization was not high, i.e. ca. 30% in DFM and 8% in DFG. Accumulation of high Mn was not prevented in inoculated seedlings. The hyphal mantle of mycorrhizal root tips accumulated divalent cations such as Ca, but not Mn, thus not providing a barrier against excessive Mn uptake into the plants associated with R. subareolatus.     

Long-range charge transport through double-stranded DNA mediated by manganese or iron porphyrins

Guanine oxidation by electron transfer results in the formation of a guanine radical cation, which is at the origin of long-range charge transport through double-stranded DNA. It is possible to observe guanine lesions at a long distance from the oxidative reagent covalently bound to DNA owing to the migration of the positive hole in the DNA pi-stacks. This phenomenon of long-range hole transport is classically studied in the literature with photosensitizers used as one-electron oxidants. It is shown in the present work that the process of long-range charge transport and the concomitant formation of guanine lesions at a long distance can be observed also in the case of two-electron oxidants. This is the signature of the formation of a transient guanine radical cation in the course of the two-electron abstraction process and consequently evidence of the separated one plus one electron abstraction steps. Long-range charge transport is likely to be a universal mechanism for any two-electron oxidant acting by electron abstraction provided that the second electron abstraction is slower than hole transfer.     

Microbially initiated pitting on 316L stainless steel

Pitting corrosion of 316L stainless steel ennobled in the presence of manganese-oxidizing bacteria, Leptothrix discophora, was studied in a low-concentration sodium chloride solution. Corrosion coupons were first exposed to the microorganisms in a batch reactor until ennoblement occurred, then sodium chloride was added, which initiated pitting. The pits had aspect ratios (length divided by width) and shapes closely resembling the aspect ratio and the shape of the bacteria, which suggested that the microorganisms were involved in pit initiation.     

Release of Fe,Mn and P in a calcareous vertisol and yield of upland rice as influenced by presowing soil water treatments

Summary A field experiment was conducted on a calcareous vertisol at Mahatma Phule Agricultural University, Rahuri to study the release of Fe, Mn and P in soil and yield of two rice cultivars due to different soil water treatments for 15 days prior to sowing. Soil saturation (daily two irrigations) for 15 days prior to sowing increased the supply of Fe, Mn and P in soil at sowing as a result of reduction in pH and Eh. Dry matter yield at different growth stages as well as grain yields of Karjat 184 (dwarf) and Tuljapur 1 (tall) also increased due to presowing soil saturation treatment. Tuljapur 1 yielded more than Karjat 184 when grown under upland conditions. Laboratory incubation studies showed reduction in soil pH (from 8.6 to 7.5) and Eh (from +501 to +362 mv) at the end of 15 days under soil submergence treatment. Availability of Fe, Mn and P was also found to be increased.     

A map of rye chromosome 2R using isozyme and morphological markers

Summary The segregation of isozymic loci for leaf peroxidases (L2Per) has been investigated in backcrosses and F₂ offspring of rye lines having purple seeds (Ps) and monstrosum ears (mo). The Ps, L2Per-3b, mo, and L2Per-2 loci were linked. The Ps and mo loci have been previously located on the 2R chromosome, and the L2Per-3b and L2Per-2 loci have been located on the 2RS chromosome arm. The results favor the gene order Ps ... L2Per-3b ... mo ... L2Per-2 or Ps ... mo... L2Per-3b ... L2Per-2. The position of the loci relative to the centromere is still not known, but the obtained results suggest that the mo locus could be located on the 2RS chromosome arm. On the basis of previously reported linkage groups, the most probable arrangement of the loci located on chromosome 2R is: dw2 ... Ps ... (L2Per-3a ... L2Per-3b ... mo) ... L2Per-2. It has not been possible to know the position of L2Per-4 loci (also located on 2RS chromosome arm) relative to L2Per-3a and L2Per-3b loci.     

Quality of micropropagated plants—Vitrification

Summary Vitrification-Hyperhydrous shoot development, effects the survival and quality of several micropropagated plants ex-vitro. The leaves which are the immediate organ to be affected, exhibit abnormal morphology and physiology. Leaf malfunction is apparently a stress response to very rich media and high relative humidity. The understanding of the underlying mechanism of vitrification and its control in vitro can contribute to a more efficient micropropagation. Vitrification was found to be associated with elevated ethylene production which was related to hypolignification and poor cell wall development. Liquid and low agar media induced callose formation along with reduced and disoriented cellulose biosynthesis, manifested also in non-functioning guard cells. Malfunctioning stomata, in addition to defective cuticle contributed to increased transpiration and desiccation of in vitro formed leaves. The activity of various enzymes, associated with cell wall synthesis, was low and total proteins in normal leaves was higher than in vitreous ones. Various measures were found to reduce vitrification; lowered matrix and water potential in the medium, reduction in RH, low NH ₄ ⁺ , changes in Ca⁺⁺ levels and the removal of ethylene. These measures improved leaf morphogenesis, survival and the quality of several micropropagated plant species. Presented in the Session-in-Depth Transition of Plants From Culture to Establishment In Vivo,“ at the 41st Annual Meeting of the Tissue Culture Association, Houston, Texas, June 10–13, 1990.     

Micronutrient availability to cereals from calcareous soils

Summary The mechanism of higher grain production of wheat (Triticum aestivum L.) by four tillage methods was explored on a sandy calcareous soil of Sahl-Al Jafara, Libya, during the year 1976–77. Tillage methods increased grain yield and dry matter weight at the boot stage in the order of no-tillage<rotovator=disc plough < subsoiler. Rotovation to 15 cm and disc ploughing to 25 cm depth enhanced grain production mainly by eliminating weed competition. In both the cases, roots penetrated < 25 cm where plough-pan existed.Further yield increases by 50 cm deep subsoiling seems to be mainly explained by N and Cu rise in plants from their marginal to optimum levels and by reduction of Mn deficiency in plant shoots. Penetration of roots beyond the 25 cm plough-pan apparently resulted in higher absorption of these nutrients from leached or native soil supplies. Subsoiling also resulted in greater Zn concentration in plant shoots which, under marginal to deficient conditions, will also increase grain production.     

Trace elements in ancient Peruvian mummy hair: A preliminary report

Hair samples of 46 prehistoric mummies from five different pre-Inca sites in Peru were analyzed for Ca, Sr, Ni, Mn, and Ba by DCP/AES. The five sites displayed differing burial customs: whereas the dead of Cahuachi (n=13), Huayuri (n=2) and Brujo (n=5) had been interred unwrapped in simple stone pits, the mummies of Las Trancas (n=17) and Pacatnamu (n=9) had been granted protection by fabrics and wooden coffins. At the sites with no protection, the hair samples contained extremely high concentrations of Ca and Sr which by far exceeded the usual physiological ranges. This can probably be explained by contamination from the surrounding soil. In contrast, the protected depositions of Las Trancas and Pacatnamu exhibited Ca and Sr concentrations within the present range of variation. This may indicate that favourable conditions had prevented contamination in these cases. For Mn the same trend can be observed, both Cahuachi and Huayuri samples showed markedly increased values. For Ni and Ba on the other hand no correlation with the type of interment was found. In the two non-contaminated series, the mean values of Mn, Ba, and Ni were considerably higher in Las Trancas than in Pacatnamu. As Mn, Ni, and Ba tend to occur in higher concentrations in vegetable than in animal food items, these differences may indicate a differential availability of animal protein at the two locations