Suppression of Programmed Cell Death by Intracellular cAMP Is not Mediated by Expression of Genes Encoding an Inhibitor of Apoptosis

The elevation of intracellular cAMP content is accompanied by expression of genes whose promoter contains a Ca²⁺-cAMP responsive element. In vascular smooth muscle cells (VSMC), activation of cAMP signaling blocks apoptosis triggered by serum deprivation. In the present study we investigated the role of gene expression in the inhibition of apoptosis by cAMP. In VSMC transfected with E1A adenovirus, incubation in the absence of serum for 6 h led to 20-fold elevation of chromatin fragmentation and 10-fold activation of caspase-3 activity, these being employed as markers of apoptosis. Forskolin induced activation of cAMP signaling was accompanied by 50% elevation of RNA synthesis and completely abolished the development of apoptosis during the initial 6 h incubation in growth factor-free medium. In 12 h apoptosis in forskolin-treated VSMC was slowly developed and after 24 h the content of chromatin fragments was 2-fold less than in control cells. Addition of actinomycin D and cycloheximide completely blocked RNA synthesis and decreased protein synthesis by 80%, respectively. Neither compound affected baseline apoptosis or its inhibition by forskolin. More than 70 newly phosphorylated proteins were observed by 2D-electrophoresis of VSMC after incubation with forskolin for 3 h; in 24 h the number of phosphoproteins triggered by forskolin was decreased by 2-3-fold. These results show that suppression of VSMC apoptosis under activation of cAMP signaling is mediated via posttranslational modification of pre-existing intermediates of the apoptotic machinery rather than by de novo synthesis of inhibitors of programmed cell death.     

Ability of the antagonistic yeast Cryptococcus albidus to control Botrytis cinerea in strawberry

The yeast Cryptococcus albidus, originally isolated from mature strawberry fruits, was tested for antagonistic activity against Botrytis cinerea, the causal agent of grey mould in strawberries. Conidial germination and germ tube growth of conidia of B. cinerea were inhibited by a cell suspension of the antagonist in aqueous strawberry fruit pulp suspension (1%) after 6 and 24 hours of incubation. Application of a cell suspension (1 × 10⁶ cells/ml) on detached strawberry leaf disks incubated at 10°C reduced incidence and conidiophore density of B. cinerea by 86 and 99%, respectively, but effectiveness was reduced at higher temperatures. Treatments with C. albidus during bloom of strawberries reduced incidence of grey mould on ripe strawberry fruits after harvest by 33, 28 and 21% in three years of field trials. The effectiveness of the yeast was increased when formulation substances (alginate, xanthan and cellulose) were added to the cell suspension.     

The effect of lead on the cell cycle in the root meristem ofAllium cepa L.

Summary Allium cepa (L.) adventitious roots were treated with lead (2.5 mg of Pb²⁺ [from Pb(NO₃)₂] per dm³) for 30–72 h. The cell cycle was studied by pulse labeling with [³H]thymidine. Mitotic activity kinetics, occurrence of disturbed mitoses (c-mitoses), and level of DNA synthesis were examined. It was found that lead prolonged the cell cycle and that cells in two phases of the cycle, G₂ and S, differed in their sensitivity to lead. Cells in G₂ were more sensitive; lead lengthened their cycle by 216% and disturbed the course of cell division by causing c-mitoses. Cells in S phase were less sensitive. Their cell cycle was longer by 55%. They went through their G₂ phase without major disturbances, mitosis in these cells was normal. During treatment ofA. cepa with lead, its destructive effects on cells were exerted only during the first few hours (around 6 h) of incubation. That is when the inhibition of mitotic activity, numerous disturbances of cell division, a decline in the number of cells synthesizing DNA, and a lower level of DNA synthesis were observed. As the incubation continued, the above processes were found to return to normal. In the discussion, data are presented supporting the hypothesis that during the initial period of exposure ofA. cepa to lead, this metal enters both the root apoplast and symplast, exerting a destructive effect on cells, while later, lead penetrates only into the root apoplast, and in this way remains harmless to cells.     

Differences in thermotolerance induced by heat or sodium arsenite: cell killing and inhibition of protein synthesis

Chinese hamster ovary (CHO) cells became thermotolerant after treatment with either heat for 10 min at 45.5 degrees C or incubation in 100 microM sodium arsenite for 1 h at 37 degrees C. Thermotolerance was tested using heat treatment at 45 degrees C or 43 degrees C administered 6-12 h after the inducing agent. At 45 degrees C thermotolerance ratios at 10(-2) isosurvival levels were 4.2 and 3.8 for heat and sodium arsenite, respectively. Recovery from heat damage as measured by resumption of protein synthesis was more rapid in heat-induced thermotolerant cells than in either sodium arsenite-induced thermotolerant cells or nonthermotolerant cells. Differences in inhibition of protein synthesis between heat-induced thermotolerant cells and sodium arsenite-induced thermotolerant cells were also evident after test heating at 43 degrees C for 5 h. At this temperature heat-induced thermotolerant cells were protected immediately from inhibition of protein synthesis, whereas sodium arsenite-induced thermotolerant cells, while initially suppressed, gradually recovered within 24 h. Furthermore, adding cycloheximide during the thermotolerance development period greatly inhibited sodium arsenite-induced thermotolerance (SF less than 10(-6] but not heat-induced thermotolerance (SF = 1.7 X 10(-1] when tested with 43 degrees C for 5 h. Our results suggest that both the development of thermotolerance and the thermotolerant state for the two agents, while similar in terms of survival, differed significantly for several parameters associated with protein synthesis.     

Investigation of the initial stages of interaction of the bacteriumAzospirillum brasilense with wheat seedling roots: Adsorption and root hair deformation

The initial stages of colonization of wheat roots by cells ofAzospirillum brasilense strains 75 and 80 isolated from soils of the Saratov oblast were studied. The adsorption of azospirilla on root hairs of soft spring wheats rapidly increased in the first hours of incubation, going then to a plateau phase. Within the first 15 h of incubation, exponential-phase cells were adsorbed more intensively than stationary-phase cells. Conversely, stationary-phase cells were adsorbed more intensively than exponential-phase cells, if the period of azospirilla incubation with the wheat roots was extended. As the time of incubation increased, the attachment of azospirilla to the wheat roots became stronger. The effect of cell attachment to root hairs was strain-dependent; the number of adsorbed cells of a given strain of azospirilla was greater in the case of host wheat cultivars. The deformation of wheat root hairs was affected by the polysaccharide-containing complexes isolated from the capsular material of azospirilla. The suggestion is made that common receptor systems are involved in the adsorption of azospirilla on roots and in root hair deformation     

Oxidative phosphorylation in nuclei isolated from rat thymus

1. Nuclei were isolated from rat thymus in 0.25 M sucrose-3 mM CaCl₂. Fractionation of thymus tissue showed that the nuclear fraction could be contaminated with 10% intact cells at the most.

2. The nuclear fraction contained about 50% of the cellular ATP. Under anaerobic conditions nuclear ATP is degraded. When, after an anaerobic incubation, the nuclei are incubated under aerobic conditions endogenous nuclear ATP is resynthesized. The amount of ATP found cannot be accounted for by mitochondria or intact cells. It could also be shown that the ATP synthesis is not due to such contamination.

3. Nuclear ATP synthesis and respiration were inhibited by amytal, rotenone, and carbon monoxide. The latter inhibition was reversed by light. 2,4-Dinitrophenol abolished ATP synthesis and accelerated respiration. Oligomycin inhibited respiration and phosphorylation. The inhibition of respiration by oligomycin could be released by dinitrophenol. ATP synthesis was also inhibited by lewisite. This inhibition could be reversed by BAL. No inhibition, however, was found with arsenite or arsenite + BAL.

4. A P:O ratio between 0.6 and 1.0 was obtained for nuclear phosphorylation. This must be considered as a minimal value.

5. It is concluded that thymus nuclei are capable of respiratory-chain-linked oxidative phosphorylation.     

Use of immobilized cells of the strainCorynebacterium sp. for 4-nitrophenol degradation

4-Nitrophenol degrading bacterial strainCorynebacterium sp. 8/3 was isolated from chemically polluted soil. The product of cometabolic transformation of 4-nitrophenol was identified as 4-nitrocatechol., Effect of immobilization (encapsulation in calcium alginate) ofCorynebacterium sp. cells on the process of 4-nitrophenol transformation was investigated. 4-Nitrophenol was converted by encapsulated cells and encapsulation had a protective effect, on 4-nitrophenol degrading bacteria in repeated cycles of incubation. Transformation of 4-nitrophenol to 4-nitrocatechol by encapsulated cells was influenced by pH of medium but was not influenced by concentration of alginate and CaCl₂. The count of viable cells in alginate beads declined approximately by one order of magnitude after 10 d of incubation. Presented at the 4th Mini-Symposium on Biosorption and Microbial Degradation, Prague, Czech Republic, November 26–29, 1996.     

Calcium alginate entrapment of the yeast Rhodosporidium toruloides for the kinetic resolution of 1,2-epoxyoctane

Resting cells of the yeast Rhodosporidium toruloides (UOFS Y-0471) were immobilised in calcium alginate beads for the enantioselective kinetic resolution of racemic-1,2-epoxyoctane. The initial activity exhibited by immobilised cells was almost 50% lower than that of the free counterpart but was extremely stable when compared to the free cells. The concentration of the immobilised biomass had no effect on apparent enzyme activity but did lead to a decrease in single cell activity. An increase in both the alginate and CaCl₂ concentrations used for bead preparation led to a decrease in enzyme stability. An increase in the alginate concentration led to an increase in bead diameter. The stoichiometric equation for cross-linking of alginate was only obeyed when CaCl₂ concentrations higher than 0.4 M were utilised for bead preparation.     

Heme-regulated inhibitor kinase-mediated phosphorylation of eukaryotic translation initiation factor 2 inhibits translation, induces stress granule formation, and mediates survival upon arsenite exposure

Exposure to arsenite inhibits protein synthesis and activates multiple stress signaling pathways. Although arsenite has diverse effects on cell metabolism, we demonstrated that phosphorylation of eukaryotic translation initiation factor 2 at Ser-51 on the alpha subunit was necessary to inhibit protein synthesis initiation in arsenite-treated cells and was essential for stress granule formation. Of the four protein kinases known to phosphorylate eukaryotic translation initiation factor 2alpha, only the heme-regulated inhibitor kinase (HRI) was required for the translational inhibition in response to arsenite treatment in mouse embryonic fibroblasts. In addition, HRI expression was required for stress granule formation and cellular survival after arsenite treatment. In vivo studies elucidated a fundamental requirement for HRI in murine survival upon acute arsenite exposure. The results demonstrated an essential role for HRI in mediating arsenite stress-induced phosphorylation of eukaryotic translation initiation factor 2alpha, inhibition of protein synthesis, stress granule formation, and survival.     

Polysaccharide production by immobilized Aureobasidium pullulans cells in batch bioreactors

Cells of the fungus Aureobasidium pullulans ATCC 201253 were entrapped within 4% agar cubes or 5% calcium alginate beads and were examined for their production of the polysaccharide pullulan in batch bioreactors. The batch bioreactors were utilized twice for 168 hours of polysaccharide production in medium containing corn syrup as a carbon source. The agar-entrapped cells produced nearly equivalent pullulan concentrations during both production cycles. The alginate-entrapped cells produced higher polysaccharide levels during the second cycle compared to the levels observed during the initial cycle. The agar-entrapped cells elaborated a polysaccharide with a higher pullulan content than did the alginate-entrapped cells during both production cycles.     

白花丹素对E.coli藻酸盐合成的抑制作用

细菌分泌的胞外多糖在生物被膜的形成和发展过程中发挥着重要作用。通过测定白花丹素对大肠埃希菌10389菌株(E.coli 10389)藻酸盐合成的影响及其对rse A和rpo E基因表达量的影响,探讨白花丹素对大肠埃希菌生物被膜(biofilm,BF)形成的抑制作用及机制。研究结果显示,白花丹素能抑制E.coli 10389生物被膜的形成,其抑杀E.coli 10389的最低抑菌浓度(minimum inhibitory concentration,MIC)和最低杀菌浓度(minimal bactericidal concentration,MBC)分别为16和64μg/mL。白花丹素对成熟BF内的细菌也有抑制和杀灭作用,其抑杀E.coli 10389成熟BF内细菌的MIC和MBC分别为64和128μg/mL。白花丹素能够抑制E.coli 10389藻酸盐的合成,其中1/2MIC的白花丹素作用E.coli 10389 24 h后,与对照组比,藻酸盐的合成量降低了34.83%(P0.01)。白花丹素可显著影响E.coli 10389 rse A和rpo E基因的相对表达量,其中1/2MIC的白花丹素作用E.coli 10389 24 h后,与对照组相比,rse A的表达量上调了17.43%,rpo E的表达量降低了12.8%(P0.05)。结果表明,白花丹素能够抑制E.coli 10389 BF的形成,其作用机制可通过影响rse A和rpo E的基因表达量,进而抑制藻酸盐的合成来抑制大肠埃希菌生物被膜的形成。     

Overexpression of alginate lyase of <Emphasis Type="Italic">Pseudoalteromonas elyakovii</Emphasis> in <Emphasis Type="Italic">Escherichia coli</Emphasis>, purification,and characterization of the recombinant alginate lyase

The alyPEEC gene encoding alginate lyase from marine bacterium Pseudoalteromonas elyakovii IAM 14594 was subcloned into pBAD24 with arabinose promoter and sequenced, and overexpressed in TOP10 strain of E. coli after arabinose induction. Expression levels of alyPEEC gene in E. coli cells were over 39.6-fold higher than those in P. elyakovii IAM 14594 cells. The molecular mass of purified alginate lyase from the engineered E. coli cells was estimated to be 32.0 kDa. Optimum pH and temperature of the alginate lyase activity were 7.0 and 30 °C, respectively. The enzyme was unstable on heating and in acidic and alkaline solution. The enzyme activity was stimulated by the MgCl₂, NaCl, KCl, CaCl₂, BaCl₂ and MnCl₂, but was inhibited by the addition of 1.0 mM of EGTA, EDTA, SDS, ZnSO₄, AgNO₃, and CoCl₂. All the alginate, polyM and polyG could be converted into oligosaccharides with more than tetrasaccharides by the purified recombinant alginate lyase, suggesting that the recombinant alginate lyase produced by the engineered E. coli has highly potential application in seaweed genetics, food and pharmaceutical industries.     

Preparation of mixed alginate elicitors with high activity for the efficient production of 5′-phosphodiesterase by Catharanthus roseus cells

When various autoclaved microbial cells suspensions (exogenous elicitors) were added to Catharanthus roseus cell cultures, its growth was inhibited but 5′-phosphodiesterase (PDase) production was stimulated. The greatest effect was with autoclaved Alteromonas macleodii: the dry cell concentration decreased from 13 to 10.9 mg/ml while PDase production increased from 0.022 to 0.235 U/ml. A combination of A. macleodii (as exogenous elicitor) and 0.1%(w/v) alginate oligomers (AO: acting as both endogenous elicitor and scavenger of active oxygen species) minimized the cell growth inhibition but enhanced PDase production (0.474 U/ml) about 20 times higher than the control (no addition). The method for the preparation of mixed alginate elicitors with high activities containing exogenous elicitor (autoclaved A. macleodii), endogenous elicitor (AO), and trans-4,5-dihydroxy-2-cyclopenten-1-one was developed. The mixed alginate elicitors significantly promoted PDase production (2.67 U/ml) by C. roseus, and the productivity was increased 120-fold compared to the control without cell growth inhibition.     

Light and Stomatal Metabolism : II. Effects of Sulfite and Arsenite on Stomatal Opening and Light Modulation of Enzymes in Epidermis

The effect of sulfite and arsenite on stomatal opening and light modulation of enzymes was examined in isolated epidermal strips of Pisum sativum L. var Little Marvel leaves. Sulfite or arsenite at 10 micromolar rapidly inhibited the stomatal opening process in light. Light activation of phosphoenolpyruvate carboxylase and NADP-malate dehydrogenase was completely diminished when the epidermal strips were incubated for 2 hours in light with either sulfite or arsenite at 10 micromolar. The data obtained suggest that the inhibition of stomatal opening by sulfite or arsenite in light might result from the inhibition of light modulation of key enzymes in guard cells.     

Plasmid-determined resistance to arsenic and antimony inPseudomonas aeruginosa

Resistance to arsenic salts in aPseudomonas aeruginosa clinical isolate was shown to be determined by a 100 kb transferable plasmid. The resistance pattern included arsenate, arsenite, and antimonate ions. Arsenate and arsenite resistances were inducible by previous exposure of cultures to subinhibitory amounts of either of the two ions. Phosphate ions protectedP. aeruginosa cells from the toxic effects of arsenate but did not alter arsenite toxicity.     

Cell immobilization technique for the enhanced production of alpha-galactosidase by Streptomyces griseoloalbus

Streptomyces griseoloalbus was immobilized in calcium alginate gel and the optimal immobilization parameters (concentrations of sodium alginate and calcium chloride, initial biomass and curing time) for the enhanced production of alpha-galactosidase were determined. The immobilization was most effective with 3% sodium alginate and 0.1M calcium chloride. The optimal initial biomass for immobilization was approximately 2.2g (wet wt.). The alginate-entrapped cells were advantageous because there was a twofold increase in the enzyme yield (55 U/ml) compared to the highest yield obtained with free cells (23.6 U/ml). Moreover, with immobilized cells the maximum yield was reached after 72 h of incubation in batch fermentation under optimal conditions, whereas in the case of free cells the maximum enzyme yield was obtained only after 96 h of incubation. The alginate beads had good stability and also retained 75% ability of enzyme production even after eight cycles of repeated batch fermentation. It is significant that this is the first report on whole-cell immobilization for alpha-galactosidase production.     

Spheroplast induction inAnabaena variabilis Kütz andA. azollae stras

Summary Spheroplasts were obtained by lysozyme treatment of 48 hour (4– 8cells) akinete germlings of the cultured cyanobacteriaAnabaena variabilis andA. azollae originally isolated from the leaf cavity of the fernAzolla pinnata. The osmotic stabilizer was 0.5 M sucrose. At least 50% of the cells in a short filament became spheroplasts after 1–4 hours in lysozyme (1 mg/ml) in incubation medium at 34 °C, with greater than 75% viability after 2 hours. The spheroplasts were osmotically fragile and showed intense chlorophyll autofluorescence in UV light. In phase microscopy, treated cells appeared larger, became spherical and lost some of their optical refraction. Transmission electron microscopy confirmed the loss of the peptidoglycan layer and the partial remains of the outer membrane after lysozyme exposure. We previously obtained protoplasts ofAzolla fern leaf cells so that we now can study the recognition sites in both members of theAzolla/Anabaena nitrogen fixing symbiosis during cell wall degradation and regeneration.     

Degradation of ethylbenzene by free and immobilized <Emphasis Type="Italic">Pseudomonas</Emphasis><Emphasis Type="Italic">fluorescens-</Emphasis>CS2

Pseudomonas fluorescens-CS2 metabolized ethylbenzene as the sole source of carbon and energy. The involvement of catechol as the hydroxylated intermediate during the biodegradation of ethylbenzene was established by TLC, HPLC and enzyme analysis. The specific activity of Catechol 2,3-dioxygenase in the cell free extracts of P. fluorescens-CS2 was determined to be 0.428 μmoles min⁻¹ mg⁻¹ protein. An aqueous-organic, Two-Phase Batch Culture System (TPBCS) was developed to overcome inhibition due to higher substrate concentrations. In TPBCS, P. fluorescens-CS2 demonstrated ethylbenzene utilization up to 50 mM without substrate inhibition on inclusion of n-decanol as the second phase. The rate of ethylbenzene metabolism in TPBCS was found enhance by fivefold in comparison with single phase system. Alternatively the alginate, agar and polyacrylamide matrix immobilized P. fluorescens-CS2 cells efficiently degraded ethylebenzene with enhanced efficiency compared to free cell cultures in single and two-phase systems. The cells entrapped in ployacrylamide and alginate were found to be stable and degradation efficient for a period of 42 days where as agar-entrapped P. fluorescens was stable and efficient a period of 36 days. This demonstrates that alginate and polyacrylamide matrices are more promising as compared to agar for cell immobilization.     

Stimulatory effects of protein synthesis inhibitors on the spreading rate of 3T3 cells

Three protein synthesis inhibitors, puromycin, cycloheximide and anisomycin were found to increase the rate of spreading of Swiss-3T3 cells after 1 h incubation in the presence of low concentrations of serum. Data from experiments with anisomycin suggest that this effect is roughly proportional to the extent of inhibition of protein synthesis.