A comparison of mechanisms of desiccation tolerance among three angiosperm resurrection plant species

The mechanisms of protection against mechanical and oxidative stress were identified and compared in the angiosperm resurrection plants Craterostigma wilmsii, Myrothamnus flabellifolius and Xerophyta humilis. Drying-induced ultrastructural changes within mesophyll cells were followed to gain an understanding of the mechanisms of mechanical stabilisation. In all three species, water filled vacuoles present in hydrated cells were replaced by several smaller vacuoles filled with non-aqueous substances. In X. humilis, these occupied a large proportion of the cytoplasm, preventing plasmalemma withdrawal and cell wall collapse. In C. wilmsii, vacuoles were small but extensive cell wall folding occurred to prevent plasmalemma withdrawal. In M. flabellifolius, some degree of vacuolation and wall folding occurred, but neither were sufficient to prevent plasmalemma withdrawal. This membrane was not ruptured, possibly due to membrane repair at plasmodesmata junctions where tearing might have occurred. In addition, the extra-cytoplasmic compartment appeared to contain material (possibly similar to that in vacuoles) which could facilitate stabilisation of dry cells.Photosynthesis and respiration are particularly susceptible to oxidative stress during drying. Photosynthesis ceased at high water contents and it is proposed that a controlled shut down of this metabolism occurred in order to minimise the potential for photo-oxidation. The mechanisms whereby this was achieved varied among the species. In X. humilis, chlorophyll was degraded and thylakoid membranes dismantled during drying. In both C. wilmsii and M. flabellifolius, chlorophyll was retained, but photosynthesis was stopped due to chlorophyll shading from leaf folding and anthocyanin accumulation. Furthermore, in M. flabellifolius thylakoid membranes became unstacked during drying. All species continued respiration during drying to 10% relative water content, which is proposed to be necessary for energy to establish protection mechanisms. Activity of antioxidant enzymes increased during drying and remained high at low water contents in all species, ameliorating free radical damage from both photosynthesis and respiration. The nature and extent of antioxidant upregulation varied among the species. In C. wilmsii, only ascorbate peroxidise activity increased, but in M. flabellifolius and X. humilis ascorbate peroxidise, glutathione reductase and superoxide dismutase activity increased, to various extents, during drying. Anthocyanins accumulated in all species but this was more extensive in the homoiochlorophyllous types, possibly for protection against photo-oxidation.     

Rapid, extensive and reversible vacuolation of Schizosaccharomyces pombe induced by amphotericin B

Abstract The fission yeast Schizosaccharomyces pombe has no large vacuoles under normal growth conditions, although budding yeasts usually have large central vacuoles. The minimum inhibitory concentration of amphotericin B to S. pombe was 0.5 μg ml⁻¹; treatment with 0.2 μg ml⁻¹ for 20 min induced rapid and extensive vacuolation in S. pombe exponential phase cells. Growth rate of the cells with 0.2 μg ml⁻¹ amphotericin B was much reduced for 6 h, showing extensive vacuolation. Vacuolation in itself was not fatal: on removal of the drug, most cells recovered gradually and eventually multiplied.     

The V-ATPase inhibitors concanamycin A and bafilomycin A lead to Golgi swelling in tobacco BY-2 cells

Summary. Concanamycin A and bafilomycin A are well-known inhibitors of V-ATPase activity. It is known that they interfere with intracellular protein trafficking in both animal and plant cells, but a cellular target for their action in plant cells has not been defined. Here we show that treatment with these inhibitors leads to a massive vacuolation of the Golgi apparatus. The effect is similar, but not identical, to that previously described for the Na⁺/K⁺ ionophores and is reversible after washing.     

Incidence of toxic Aeromonas isolated from food and human infection

One hundred and ninety four Aeromonas isolates (99 from food and 95 from clinical sources) were analyzed as to the species involved and the toxins produced. Of the clinical isolates of Aeromonas, 29.4% were enterotoxigenic, 43.1% were hemolytic and 89% were cytotoxigenic. Among the food isolates, 18.2% were enterotoxigenic, 17.1% were hemolytic and 72.7% were cytotoxigenic. Aeromonas sobria and Aeromonas veronii produced more enterotoxin and cytotoxin than the other isolates, whereas A. veronii and Aeromonas salmonicida produced cell-free hemolysin. Most of the isolates produced cytotoxins (81%) active on Vero (green monkey kidney) and Chinese hamster ovary cells, but only the culture supernatant of A. sobria produced vacuolation in these cell lines.     

D-galactosyl-beta1-1'-sphingosine and D-glucosyl-beta1-1'-sphingosine induce human natural killer cell apoptosis

Natural killer (NK) cells perform multiple biological functions including tumor cell lysis and eradicating virally infected cells. Here, we report for the first time that D-galactosyl-beta1-1' sphingosine and D-glucosyl-beta1- 1' sphingosine damage human NK cells. We show that these cells express T-cell-associated gene-8, the receptor for glycosphingolipids. D-galactosyl-beta1-1' sphingosine and D-glucosyl-beta1-1' sphingosine induce the in vitro chemotaxis of human NK cells. Both D-galactosyl-beta1-1' sphingosine and D-glucosyl-beta1-1' sphingosine inhibit the cytotoxicity and IFN-gamma secretion by these cells. Further analysis shows that the glycosphingolipids D-galactosyl-beta1-1' sphingosine and D-glucosyl-beta1-1' sphingosine but not any other lipid examined, which include D-lactosyl-beta1-1' sphingosine, sphingosine 1-phosphate, sphingosine, lysophosphatidic acid, and phosphatidic acid, induce the apoptosis, globoid-like formation, and multinucleation in human NK cells. These results may have important implications on diseases where glycosphingolipids accumulate.     

A novel dodecadepsipeptide, cereulide, isolated from Bacillus cereus causes vacuole formation in HEp-2 cells

Abstract A HEp-2 cell-vacuolation factor was extracted and purified from the culture supernatant of a Bacillus cereus strain which caused emetic-syndrome food poisoning. The final preparation was chemically pure, and the toxin was named as cereulide. Mass spectrometry, NMR studies and chemical degradation revealed that the cereulide is a cyclic dodecadepsipeptide, (D-O-Leu-D-Ala- L-O-Val-L-Val)₃, which is closely related to the potassium ionophore, valinomycin.     

Acridine orange accumulation in acid organelles of normal and vacuolated frog skeletal muscle fibres

The spatial distribution of acid membrane organelles and their relationships with normal and vacuolated transverse tubules has been studied in living frog skeletal muscle fibres using confocal microscopy. Acridine orange (AO) was used to evaluate acid compartments, while a lipophilic styryl dye, RH 414, was employed to stain the membranes of the T-system. AO accumulated in numerous spherical granules located near the poles of nuclei and between myofibrils where they were arranged in short parallel rows, triplets or pairs. AO granules could be divided into three groups: green (monomeric AO), red (aggregated AO), and mixed green/red. As demonstrated by lambda-scanning, most granules were mixed. Double staining of muscle fibres with AO and RH 414 revealed almost all AO granules located near the transverse tubules. Vacuolation of the T-system was induced by glycerol loading and subsequent removal. The close juxtaposition of AO granules and the T-system was preserved in vacuolated fibres. The lumens of vacuoles did not accumulate AO. It is concluded that AO granules represent an accumulation of AO in lysosome-related organelles and fragmented Golgi apparatus and a possible functional role of the spatial distribution of such acidic compartments is discussed.     

幽门螺杆菌致细胞空泡变性作用

This study was designed to observe vacuolation effect of Helicobacter pylori on gastric epithelial cells.The H.pylori isolates derived from patiens with peptic ulcer,chronic gastritis and gastric cancer were plated on common selective medium and their vacuolation effects on SGC\|7901 cells were compared. The percentage of H.pylori (Tox +) strain in clinical isolates from different gastroduodenal diseases had no significant difference.The toxicity of the H.pylori (Tox +) strain from peptic ulcer was si…     

Design,synthesis and anticancer activity of constrained sphingolipid-phenoxazine/phenothiazine hybrid constructs targeting protein phosphatase 2A

Inspired by the cytotoxicity of perphenazine toward cancer cells and its ability to activate the serine/threonine protein phosphatase 2A (PP2A), we prepared series of ether-carbon linked analogs of a constrained synthetic sphingolipid analog 3, known for its cytotoxicity, nutrient transporter down-regulation and vacuolation properties, incorporating the tricyclic neuroleptics phenoxazine and phenothiazine to represent hybrid structures with possible synergistic cytotoxic activity. While the original activity of the lead compound 3 was diminished by fusion with the phenoxazine or phenothiazine tethered moieties, the corresponding 3-pyridyltetryl ether analog 10 showed cytotoxicity and nutrient transporter down-regulation similar to the lead compound 3, although it separated these PP2A-dependent phenotypes from that of vacuolation.     

Evidence of apoptotic effects of 2,4-D and butachlor on walking catfish, Clarias batrachus, by transmission electron microscopy and DNA degradation studies

Apoptosis or programmed cell death is characterized morphologically by chromatin condensation, cell shrinkage, fragmentation of the nucleus and cytoplasm, and consequently formation of apoptotic bodies. It has also been best characterized by the cleavage of DNA into nucleosomal size fragments of 180-200 bp or multiples of the same. Contrary to this, under extreme conditions, the cells were found to show adaptive response to apoptosis and unable to regulate their own death; necrosis is therefore predominantly observed. In the present study, we showed induction of apoptosis in Clarias batrachus due to sublethal concentration of 2,4-D and butachlor at multiple exposure time. The first phase of the study involved light microscopy (LM) and transmission electron microscopy (TEM) for ultrastructural abnormalities of the germinal tissues. While, in the second phase of the study, DNA degradation of blood and hepatic tissue was resolved on agarose gel electrophoresis. In histopathological studies, large numbers of stage II oocytes were noted for nuclear blebbing irrespective of the test chemical. Some of the butachlor-exposed oocytes showed vacuolation and electron dense cytoplasm along with thickened nuclear envelope, having close association with the lysosomes on the cytoplasmic side. Some oocytes undergo nuclear blebbing having inner dense core and translucent cytoplasm. Leydig cells were slightly hypertrophied and few appeared pycnotic, a process involving necrotic changes in which the cell nuclei were characterized by rounding up and condensation resulting in hyperchromatic staining or pycnosis. In testicular tissue, spermatogonial nuclei had irregular large clumps of heterochromatin adjoining the nuclear membrane indicating initial stage of apoptotic cell death. Electrophoretic separation resulted in a ladder pattern of blood DNA and smear like pattern of hepatic DNA. These results indicate that the above herbicides are able to induce apoptosis both at molecular as well as cytological level. A reference dose or safety factor approach to calculate risk of human exposure to both chemicals is still awaited.