Growth,anatomy and enzyme activity changes in maize roots induced by treatment of seeds with low-temperature plasma

The seeds of Zea mays L. cv. KWS were exposed to low-temperature plasma (LTP) by using Diffuse Coplanar Surface Barrier Discharge (DCSBD) for 60 and 120 seconds respectively. Growth parameters, anatomy of roots and activity of some enzymes (CAT, G-POX, SOD and DHO) isolated from roots grown from the seeds treated by LTP were evaluated. Our results indicate that LTP treatment of maize seeds affects post-germination growth of seedlings and this effect depends on the duration of LTP treatment. LTP treatment in duration of 60 seconds significantly increased the length, fresh and dry weight of the roots. However, the increase in time of LTP treatment to 120 seconds had inhibitive effect on the studied growth parameters. The activities of all studied antioxidant enzymes significantly increased with the age of maize seedlings in control conditions. On the other hand the application of LTP resulted in small, mostly non significant changes in the activity of antioxidant enzymes. Significant decrease in CAT activity was observed both in 3 and 6-day old maize roots and G-POX activity in 3-day old maize roots grown from seeds exposed to LTP for 60 seconds. A small, significant increase was detected only in SOD activity in 3-day old maize roots grown from seeds treated with LTP for 120 seconds and in 6-day old maize roots treated with LTP for 60 seconds. Significantly higher DHO activity was determined in embryos isolated from seeds treated with LTP for 60 seconds. On the contrary, in roots the DHO activity decreased with the time of LTP treatment. LTP treatment of seeds did not affect the anatomy of maize roots and caused only minor changes in the isoenzyme composition of G-POX and SOD.     

Cadmium translocation by contractile roots differs from that in regular,non-contractile roots

Background and Aims Contractile roots are known and studied mainly in connection with the process of shrinkage of their basal parts, which acts to pull the shoot of the plant deeper into the ground. Previous studies have shown that the specific structure of these roots results in more intensive water uptake at the base, which is in contrast to regular root types. The purpose of this study was to find out whether the basal parts of contractile roots are also more active in translocation of cadmium to the shoot.Methods Plants of the South African ornamental species Tritonia gladiolaris were cultivated in vitro for 2 months, at which point they possessed well-developed contractile roots. They were then transferred to Petri dishes with horizontally separated compartments of agar containing 50 µmol Cd(NO₃)₂ in the region of the root base or the root apex. Seedlings of 4-d-old maize (Zea mays) plants, which do not possess contractile roots, were also transferred to similar Petri dishes. The concentrations of Cd in the leaves of the plants were compared after 10 d of cultivation. Anatomical analyses of Tritonia roots were performed using appropriately stained freehand cross-sections.Key Results The process of contraction required specific anatomical adaptation of the root base in Tritonia, with less lignified and less suberized tissues in comparison with the subapical part of the root. These unusual developmental characteristics were accompanied by more intensive translocation of Cd ions from the basal part of contractile roots to the leaves than from the apical–subapical root parts. The opposite effects were seen in the non-contractile roots of maize, with higher uptake and transport by the apical parts of the root and lower uptake and transport by the basal part.Conclusions The specific characteristics of contractile roots may have a significant impact on the uptake of ions, including toxic metals from the soil surface layers. This may be important for plant nutrition, for example in the uptake of nutrients from upper soil layers, which are richer in humus in otherwise nutrient-poor soils, and also has implications for the uptake of surface-soil pollutants.     

ST segment body surface isointegral maps in patients with arterial hypertension

In this retrospective study we analysed changes of the ST segment in patients with arterial hypertension using multi-lead body surface mapping of the electric heart field as the ST segment often shows non-specific changes and is influenced by many different conditions. We constructed isointegral maps (IIM) of chosen intervals (the first 35 ms, the first 80 ms, and the whole ST segment) in 42 patients with arterial hypertension (with and without left ventricular hypertrophy) and in the control group involving 23 healthy persons. We analysed the position and values of map extrema. Spatial distribution of voltage integrals was similar in the control group and in the "pure" hypertensives. Patients with the left ventricular hypertrophy exhibited shifts of the integral minima. Despite our expectations, the highest extrema values were found in the control group and not in the left ventricular hypertrophy group. The extrema values were similar in all hypertensives, with or without left ventricular hypertrophy. Differences could be explained neither by the influence of the age, nor by the body habitus.     

Cadmium uptake,localization and stress-induced morphogenic response in the fern Pteris vittata

Cadmium uptake, tissue localization and structural changes induced at cellular level are essential to understand Cd tolerance in plants. In this study we have exposed plants of Pteris vittata to different concentrations of CdCl₂ (0, 30, 60, 100 μM) to evaluate the tolerance of the fern to cadmium. Cadmium content determination and its histochemical localization showed that P. vittata not only takes up, but also transports and accumulates cadmium in the aboveground tissues, delocalizing it mainly in the less bioactive tissues of the frond, the trichomes and the scales. Cadmium tolerance in P. vittata was strictly related to morphogenic response induced by the metal itself in the root system. Adaptive response regarded changes of the root apex size, the developmental pattern of root hairs, the differentiation of xylem elements and endodermal suberin lamellae. All the considered parameters suggest that, in our experimental conditions, 60 μM of Cd may represent the highest concentration that P. vittata can tolerate; indeed this Cd level even improves the absorbance features of the root and allows good transport and accumulation of the metal in the fronds. The results of this study can provide useful information for phytoremediation strategies of soils contaminated by Cd, exploiting the established ability of P. vittata to transport, delocalize in the aboveground biomass and accumulate polluting metals.     

Role of the Lymphoreticular System in Prion Neuroinvasion from the Oral and Nasal Mucosa

Prion neuroinvasion from peripheral tissues involves agent replication in the lymphoreticular system (LRS) prior to entry into the nervous system. This study investigated the role of the LRS in prion neuroinvasion from the oral and nasal mucosa in wild-type and immunodeficient mice and in hamsters infected with the HY and DY strains of the transmissible mink encephalopathy (TME) agent. Following inoculation at neural sites, all hosts were susceptible to prion disease and had evidence of prion infection in the brain, but infection of the LRS was found only in scrapie-infected wild-type mice and HY TME-infected hamsters. In the LRS replication-deficient models, prion neuroinvasion was not observed following intraperitoneal or oral inoculation. However, immunodeficient mice, which have impaired follicular dendritic cells, were susceptible to scrapie following intratongue and intranasal inoculation despite the absence of PrP^Sc in the tongue or the nasal cavity. For DY TME, hamsters were susceptible following intratongue but not intranasal inoculation and PrP^Sc was limited to nerve fibers of the tongue. These findings indicate that neuroinvasion from the tongue and nasal cavity can be independent of LRS infection but neuroinvasion was partially dependent on the strain of the prion agent and/or the host species. The paucity of PrP^Sc deposition in the oral and nasal mucosa from LRS replication-deficient hosts following neuroinvasion from these tissues suggests an infection of nerve fibers that is below the threshold of PrP^Sc detection and/or the transport of the prion agent along cranial nerves without agent replication.In natural and experimental prion infections originating in the periphery, prion agent replication in the lymphoreticular system (LRS) precedes agent entry and spread in the peripheral nervous system. In the LRS, follicular dendritic cells (FDCs) are the major target of prion infection, and blocking or reversing FDC maturation can prevent scrapie agent replication in the LRS (25, 26, 28, 30, 32). Other migrating cell populations may also influence the progression of experimental prion disease (27, 36). From the LRS, centripetal spread of the prion agent to the spinal cord or brain occurs by spread along nerve fibers of the peripheral nervous system. In the central nervous system, prion agent replication can induce neurodegeneration and disease after an incubation period that can last from weeks to years. For example, in lambs from flocks with endemic scrapie, agent replication is initially detected in the gut-associated lymphoid tissues prior to proximal and distal spread in the LRS, infection of peripheral nerves that innervate the LRS, and subsequent spread to the spinal cord (19, 42). In addition, scrapie agent infection of the vagal nerve, which innervates many peripheral organs including the digestive tract, results in axonal transport directly to the dorsal motor nucleus of the vagus in the brain stem (29, 41). The role of scrapie infection in the LRS in the latter pathway of neuroinvasion is unknown. A similar pathway of prion neuroinvasion occurs in mule deer experimentally infected with the chronic wasting disease agent with the exception that early infection is also established in the lymph nodes of the upper gastrointestinal tract (37, 38). Recent studies indicate that a similar pathway of neuroinvasion occurs in natural and experimental bovine spongiform encephalopathy (BSE) following oral exposure except that agent replication in the LRS is greatly reduced and appears restricted to portions of the gut-associated lymphoid tissues (13, 20, 39).There are natural prion diseases in sheep and cattle that do not exhibit the typical distribution of the prion agent in the brain and LRS that are presumably acquired via oral prion exposure (5, 33). The absence of the abnormal isoform of the prion protein, PrP^Sc, in the LRS and dorsal motor nucleus of the vagus in atypical scrapie and the H type or L type of BSE raises the question as to whether these cases are due to infection by an alternate route(s) other than ingestion or whether these cases have an etiology that is distinct from that of acquired prion diseases. Direct prion infection of nerve fibers or terminals in highly innervated tissues, such as the mucosa in the head, has been suggested to represent potential sites of prion agent entry that would not require prior agent replication in the LRS (4, 12, 31). The presence of scrapie or BSE infection in the retina, sensory fibers of the tongue, and nasal mucosa of sheep, goat, and/or cattle suggests that the eye, tongue, or nasal cavity could be alternate sites of prion agent entry into hosts (8, 11, 15, 16, 40). Experimental prion inoculation at these mucosal sites can cause prion disease and in some cases rapid neuroinvasion (4, 9, 17, 18). Another explanation for this distribution of infection is that centrifugal spread of the prion agent away from the brain and along cranial nerves could serve as a pathway for prion infection and accumulation in these mucosal tissues (4, 10, 43).In this work, we investigated the role of the LRS in prion neuroinvasion from the oral and nasal cavities. In order to investigate neuroinvasion following neural and extraneural routes of inoculation in which prion replication is blocked in the LRS, we used two rodent models for prion infection. In muMT mice, which lack mature B cells, and in lymphotoxin-α (LTα) null mice, FDCs do not undergo maturation, and as a result, these mice do not develop clinical disease following intraperitoneal inoculation of the scrapie agent but are susceptible following direct inoculation into the brain (23, 30). In a second model, the HY and DY strains of the transmissible mink encephalopathy (TME) agent were used to investigate neuroinvasion in Syrian hamsters. The HY and DY TME agents can replicate in the nervous system, but the DY TME agent does not replicate in the LRS, and therefore, the DY TME agent is not pathogenic following intraperitoneal (i.p.) inoculation (2, 3). Following intratongue (i.t.) or intranasal (i.n.) inoculation, prion neuroinvasion was independent of scrapie agent replication in the LRS of immunodeficient mice, but evidence for scrapie infection of peripheral nerve fibers or olfactory neurons at these mucosa was lacking. In hamsters, i.t. inoculation of the HY or DY TME agent resulted in PrP^Sc deposition in nerve fibers and prion disease, but only the HY TME agent caused disease following i.n. inoculation. These findings suggest that neuroinvasion from the oral and nasal mucosa in LRS replication-deficient rodents can be independent of LRS infection, but the paucity of PrP^Sc at these mucosal sites of exposure in immunodeficient mice and DY TME-infected hamsters suggests that neuroinvasion is due to either a low-level prion infection of the nervous system at the site of inoculation or transport of the prion agent in axons in the absence of agent replication at the site of prion entry. These findings indicate that these mucosal tissues may not exhibit early evidence of infection and therefore will prove difficult to identify as a portal for agent entry.     

Saikosaponin-d,a novel SERCA inhibitor,induces autophagic cell death in apoptosis-defective cells

Autophagy is an important cellular process that controls cells in a normal homeostatic state by recycling nutrients to maintain cellular energy levels for cell survival via the turnover of proteins and damaged organelles. However, persistent activation of autophagy can lead to excessive depletion of cellular organelles and essential proteins, leading to caspase-independent autophagic cell death. As such, inducing cell death through this autophagic mechanism could be an alternative approach to the treatment of cancers. Recently, we have identified a novel autophagic inducer, saikosaponin-d (Ssd), from a medicinal plant that induces autophagy in various types of cancer cells through the formation of autophagosomes as measured by GFP-LC3 puncta formation. By computational virtual docking analysis, biochemical assays and advanced live-cell imaging techniques, Ssd was shown to increase cytosolic calcium level via direct inhibition of sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase pump, leading to autophagy induction through the activation of the Ca²⁺/calmodulin-dependent kinase kinase–AMP-activated protein kinase–mammalian target of rapamycin pathway. In addition, Ssd treatment causes the disruption of calcium homeostasis, which induces endoplasmic reticulum stress as well as the unfolded protein responses pathway. Ssd also proved to be a potent cytotoxic agent in apoptosis-defective or apoptosis-resistant mouse embryonic fibroblast cells, which either lack caspases 3, 7 or 8 or had the Bax-Bak double knockout. These results provide a detailed understanding of the mechanism of action of Ssd, as a novel autophagic inducer, which has the potential of being developed into an anti-cancer agent for targeting apoptosis-resistant cancer cells.