Role of mitochondria in ethanol tolerance of Saccharomyces cerevisiae

The presence of active mitochondria and oxidative metabolism is shown to be essential to maintain low inhibition levels by ethanol of the growth rate (), fermentation rate (v) or respiration rate () of Saccharomyces cerevisiae wild type strain S288C. Cells which have respiratory metabolism show K _i (ethanol inhibition constant) values for , v and , higher (K _i>1 M) than those of petite mutants or grande strains grown in anaerobiosis (K _i=0.7 M). In addition, the relationship between or v and ethanol concentration is linear in cells with respiratory metabolism and exponential in cells lacking respiration. When functional mitochondria are transferred to petite mutants, the resulting strain shows K _i values similar to those of the grande strain and the inhibition of and v by increasing ethanol concentrations becomes linear.     

Development of high frequency multiple shoot formation in Persian clover (<Emphasis Type="Italic">Trifolium resupinatum</Emphasis> L.)

An efficient and reliable micropropagation system for Persian clover (Trifolium resupinatum L.) was developed using different explants and media. Node, hypocotyl and cotyledonary node explants were cultured on Murashige and Skoog (MS) medium supplemented with combinations of either 6-benzyladenine (BA) and indole-3-butyric acid (IBA) or BA, Kinetin (KIN) and IBA. Direct multiple shoots developed within 6weeks in all explants in most media tested. The best shoot multiplication capacity was obtained from cotyledonary node explants on MS medium containing 7.1M BA and 1M IBA or 14.1M BA and 1M IBA. Elongated shoots were rooted on either MS medium alone or combination with different concentrations of indole-3-butyric acid (IBA), indole-3-acetic acid (IAA) and -naphthaleneacetic acid (NAA). High rooting was achieved in half strength MS medium containing 8M IBA.     

Alloxan: A growth accelerator for a nitrogen-fixing blue-green alga

Effect of Alloxan was studied on a nitrogen-fixing blue-green alga: Westiellopsis prolifica in pure cultures. Concentrations of Alloxan, 10 g to 50 g/ml stimulate the growth of the alga and increase the chlorophyll, carotin and phycocyanin content of the cultures.     

Regeneration of Elaeagnus angustifolia from leaf segments of in vitro-derived shoots

Shoot regeneration was achieved from in vitro-produced leaves of Elaeagnus angustifolia L. Half-leaf explants from the terminal part of the shoot produced more shoots than explants from the basal part of the in vitro-derived shoots on agar-solidified WPM medium supplemented with 1 M benzyladenine (BA). In liquid medium of the same formulation, compact shoots that did not elongate were formed on the explants. Leaf cross-section explants (1 mm thick) produced shoots both on solid and liquid medium with 1 M BA, whereas again compact shoots were formed with 10 M BA. Further shoot development on these explants was promoted by their transfer to fresh solid medium containing 1 M BA and 1 M gibberellic acid (GA₃).Abbreviations BA benzyladenine - GA₃ gibberellic acid - WPM woody plant medium     

Effects of GNA and other mannose binding lectins on development and fecundity of the peach-potato aphid Myzus persicae

Three mannose-binding lectins were assayed in artificial diets for their toxic and growth-inhibitory effects on nymphal development of the peach-potato aphid Myzus persicae. The snowdrop (Galanthus nivalis) lectin GNA was the most toxic, with an induced nymphal mortality of 42% at 1500 g ml^–1 (30 M) and an IC₅₀ (50% growth inhibition) of 630 g ml^–1 (13 M). The daffodil (Narcissus pseudonarcissus) lectin NPA and a garlic (Allium sativum) lectin ASA induced no significant mortality in the range 10–1500 g ml^–1, but did result in growth inhibition of 59% (NPA) and 26% (ASA) at 1500 g ml^–1 (40 M for NPA, 63 M for ASA). All three lectins were responsible for a slight but significant growth stimulation when ingested at 10 g ml^–1, reaching +26%, +18% and +11% over the control values for the garlic lectin, the daffodil lectin and the snowdrop lectin, respectively. GNA, as well as the glucose/mannose binding lectin Concanavalin A, were also provided at sublethal doses throughout the life cycle of the aphids, and effects on adult performance were monitored. Adult survival was not significantly altered, but both lectins adversely affected total fecundity and the dynamics of reproduction, resulting in significant reduction in calculated r _ms (population intrinsic rate of natural increase) on lectin-containing diets. These effects are discussed in relation to the use of transgenic plants expressing these toxic lectins for potential control of aphid populations.     

Somatic embryogenesis in callus cultures of Rosa hybrida L. cv. Landora

Callus was initiated from immature leaf and stem segments of rose (Rosa hybrida cv. Landora) and subcultured every four weeks on a basal medium of half-strength Murashige & Skoog (1962) salts plus 30 g l^-1 sucrose (1/2 MS) and supplemented with 2.2 M BA, 5.4 M NAA and 2.2–9.0 M 2,4-D. Embryogenic callus and subsequently somatic embryos were obtained from 8-week-old callus culture on 1/2 MS+2.2 M BA+0.05 M NAA+0.3 M GA₃+200–800 mg l^-1 L-proline. Long-term cultures were established and maintained for up to 16 months by repeated subculture of embryogenic callus on L-proline deficient medium. About 12% of cotyledonary stage embryos taken from cultures cold-stored at 8±1°C for 4 days germinated on 1/2 MS+2.2 M BA+0.3 M GA₃+24.7 M adenine sulphate.Abbreviations BA benzyladenine - NAA -naphthaleneacetic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - GA₃ gibberellic acid     

Plant regeneration from cotyledons of niger

Callus initiation from seedling explants of niger (Guizotia abyssinica Cass) cv. Ootacamund was found to be better on LS medium containing kinetin (1.4 M) plus 2,4-dichlorophenoxyacetic acid (9 M) than its analogues. Embryoids were induced directly from cotyledons on LS medium supplemented with 2,4,5-trichlorophenoxyacetic acid and 2,4,5-trichlorophenoxypropionic acid. When cotyledon-derived callus was subcultured onto medium with 10.7 M naphthalene-acetic acid and 2.3 M kinetin, embryogenesis was observed. Multiple shoots were obtained from cotyledonary explants in presence of MS medium containing 4.4 M benzyladenine and 11.4 M indoleacetic acid. Regenerated plants that were transferred to pots and grown to maturity were morphologically normal and fertile.Abbreviations NAA naphthaleneacetic acid - IAA indoleacetic acid - BA benzyladenine - GA₃ gibberellic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - 2,4,5-T 2,4,5-trichlorophenoxypropionic acid - 2,4,5-TP 2,4,5-trichlorophenoxypropionic acid - ABA abscisic acid     

An approach for parameter estimation of biotechnological processes

An approach for parameter estimators design of biotechnological processes (BTP) is presented in case of lack of real time information about state variables. It is based on general reaction rate models and measurements of at least one reaction rate. A general parameter estimator of BTP is designed with the help of which specific rate estimators are synthesized. Stability and convergence of an estimator of specific growth rate for a class of aerobic batch processes are proved. Its effectiveness is illustrated by simulation results. The proposed on-line parameter estimation approach can be used for design of BTP on-line variable estimation algorithms (variable observers of BTP).List of Symbols X, S, P g/l biomass, substrate and product concentrations - C g/l oxygen concentration in the culture broth - C _sg/l saturation concentration of oxygen in the culture broth - C _in, C_outg/l oxygen concentrations in the input air flow and in the outlet gasphase - F _in, F_outl/h the input air flow in the fermenter and output air flow - OUR g/(lh) oxygen consumption rate - OUR _mg/(lh) measured values of OUR - V l volume - , , l/h specific growth, consumption and synthesis rates - K _La(o) l/h specific volumetric mass transfer coefficient - D l/h dilution rate - R _X, R_S, R_Pg/(lh) biomass growth, substrate consumption and product synthesis rates - K _b matrix of yield coefficients - H_b(), H() matrices of known functions of - H(R) matrix of known functions of R - and gain matrices - a vector of the state variables - () a reactions rates vector, describing qualitative relations among the components - R() a reactions rates vector, describing qualitative and quantitative relations among the components - F a feed rates vector - Q a gaseous outflow rates vector - _b () a vector of unknown functions of - ₁() a vector of functions - (t) a vector of unknown time-varying parameters - ₂(, ) an auxiliary vector-function of and - Y _X/S, Y_X/C, Y_X/P substrate, oxygen and product yield coefficients - b maintenence coefficient - k _i(i=1...6) kinetic coefficients - C _i(i=1,2) design parameters estimate     

The units of DNA replication in the mammalian chromosomes: Evidence for a large size of replication units

The replication of chromosomal DNA in human and Chinese hamster cell populations has been studied by means of the DNA fiber autoradiography. It was found that the rate of DNA replication for one fork in human cells varies from 0.2 to 0.9 m/min, the average being 0.6 m/min. In the Chinese hamster cells the rate of DNA replication is greater, varying from 0.3 to 1.2 m/min, the average being 0.8 m/min. There are no clusters containing a great number of replication units in human and Chinese hamster cells. Sequences consisting of two or three replicons which belong to single DNA molecule have been observed, but their frequency was relatively low. The distances between the initiation points in such sequences of replicons vary from 40 to 280 m, the average value being 130 m. This value represents the minimum size of the replication units which have completed the DNA synthesis within 3 h of the S-period. The DNA synthesis in most replication units fails to be accomplished within the three hours of labelling. The process can be completed only in the fragments of DNA molecules of 40 to 200 m (the average value being 100 m) in human cells, whereas in the Chinese hamster cells the fragments of 40 to 250 m (the average being about 140 m) are completely replicated. Provided that the replication is bidirectional the complete replicons are supposed to contain two such fragments. Consequently, the greater part of replication units in mammalian cells covers the pieces of a few hundred microns in DNA molecules. The relation between replication process at the DNA molecules level and that at the metaphase chromosome level is discussed.     

Development of an L6 myoblast in vitro model of moniliformin toxicosis

L6 myoblasts were used as an in vitro model to investigate the role of moniliformin and its interaction with monensin in turkey knockdown syndrome and sudden death syndromes in poultry. Cell viability and microscopic and ultrastructural alterations noted in L6 myoblasts cultured in the presence of moniliformin (0.0–0.3 g/l) were compared to those observed in parallel cultures also containing one of the following compounds: selenium (0–0.004 ng/l), thiamine (0–0.3 g/l), or pyruvate (0–0.46 g/l). Marked dilation of the RER, membranous whorls, glycogen deposition, membrane-bound cytoplasmic inclusions and necrosis were observed in myoblasts exposed to 0.03/2-0.30 g moniliformin/l medium. Supplementation of medium with thiamine and pyruvate, or selenium, provided significant protection to cells exposed to 0.0–0.3 g/l or 0.0–0.15 g moniliformin/l, respectively. Dose-dependent differences in protein and ATP production were not detected. Myoblasts grown in medium containing 0–0.15 g moniliformin/l and 7.5–50.0 M A23187, beauvericin or monensin had degrees of cytotoxicity similar to parallel cultures receiving only an ionophore. L6 myoblasts were a useful model of moniliformin toxicosis. The findings of this study suggest cytotoxicity due to moniliformin in L6 myoblasts may be due in part to oxidative damage and altered pyruvate metabolism, and that moniliformin does not predispose myoblasts to ionophore toxicosis. This study supports the results of in vivo investigations in poultry that moniliformin and monensin do not act synergistically to induce knockdown or monensin toxicosis.     

Concentrations of fumonisin B1 in feeds associated with animal health problems

Ninety-eight samples of feeds associated with 44 cases of equine leukoencephalomalacia (ELEM) and 83 samples of feed associated with 42 cases of a porcine pulmonary edema syndrome (PPE) were analyzed for fumonisin B₁ (FB₁). For comparison purposes, 51 feed samples not associated with PPE or ELEM were also analyzed. Feed associated with ELEM contained FB₁ ranging from less than 1 g/g to 126 g/g with 75% of the cases having at least 1 sample above 10 g/g. Feeds associated with PPE ranged from less than 1 g/g to 330 g/g with 71% of the cases having at least 1 sample greater than 10 g/g. Quantitation was by high performance liquid chromatography (HPLC)/fluorescence using the fluorescamine derivative with confirmation by thin layer chromatography (TLC) and/or gas chromatography/mass spectroscopy (GC/MS).     

Adventitious shoot organogenesis and plant regeneration from cotyledons of Dalbergia sissoo Roxb., a timber yielding tree legume

A procedure is outlined to induce adventitious shoot organogenesis from semi-mature as well as mature cotyledons lacking the embryonic axis of Dalbergia sissoo Roxb., an economically important leguminous tree. Shoot buds were induced in the proximal region of the semi-mature cotyledons on Murashige and Skoog's (MS) medium supplemented with 4.44 M 6-benzyladenine (BA) and 0.26 M -naphthaleneacetic acid (NAA). These buds elongated into shoots following transfer to a similar medium containing half-strength macro-nutrients. Adventitious shoot bud formation was also induced in the mature cotyledons. However, unlike the semi-mature explants, the mature cotyledons exhibited shoot bud differentiation on MS medium containing 22.20 M BA without NAA. Pre-culture of mature cotyledons in liquid MS medium containing 8.88 M BA for a duration of 48 h improved shoot bud regeneration up to six-fold. Regenerated shoots, derived from semi-mature and mature cotyledons, rooted on half-strength MS medium containing 1.23 M and 4.92 M indole-3-butyric acid (IBA), respectively. Plantlets were acclimatized and established in soil.     

In vitro plant regeneration via somatic embryogenesis from root culture of some rhizomatous irises

A method for plant regeneration of Iris via somatic embryogenesis is described. Root and leaf pieces from in vitro-grown plants of several genotypes of rhizomatous Iris sp. were cultured in vitro. Callus induction occurred only on root cultures incubated under low light intensity (35 mol m^-2 s^-1) on two induction media containing 2,4-D (4.5 or 22.5 M), NAA (5.4 M) and kinetin (0.5 M). Somatic embryos developed after transfer of callus onto four regeneration media containing 9 or 22 M BA, or 5 M kinetin and 2 M TIBA or 9 M BA and 4 M TIBA. Plantlets could be obtained from these somatic embryos. Genotypic differences were found both in callus induction and somatic embryo formation, with I. pseudacorus responding better than I. versicolor or I. setosa. Cytological analysis performed on root tips of 80 regenerated plants revealed that two of the I. pseudacorus regenerants were tetraploid.Abbreviations 2,4-D dichlorophenoxy acetic acid - NAA naphthaleneacetic acid - BA 6-benzyladenine - TIBA 2,3,5-triiodobenzoic acid - IBA indolebutyric acid     

The induction and repression of benzene and catechol oxidizing capacity of Pseudomonas putida ML2 studied in perturbed chemostat culture

The oxidation of catechol, an intermediate in benzene catabolism, was studied using transient variations in dissolved oxygen tension (DOT) when a succinate limited steady state culture of Pseudomonas putida ML2 was perturbed with a pulse of another substrate. A model was developed and tested for the effect of fluctuations in oxidizing enzyme activity on DOT. It was found that the rate of induction of catechol oxidizing enzymes was independent of dilution rate up to a relative growth rate /_max of 0.75. Only at higher dilution rates was catabolite repression observed.Abbreviations DOT dissolved oxygen tension - K _L a gas transfer coefficient - specific growth rate - _max maximum specific growth rate - K_s substrate saturation constant     

An alternative propagation method ofAnanas through nodule culture

A micropropagation scheme forAnanas comosus Merr. was developed using nodule culture. Nodules were induced from leaf-base or chopped shoot-base explants on modified half-strength MS medium supplemented with 2.69-5.37 M NAA and 4.44 M BA and could be maintained long-term as nodules. The nodules proliferated into more nodules when chopped into pieces of 1–3 mm and placed onto the same medium. They regenerated shoots when transferred to medium supplemented with 0.54–10.74 M NAA and 0.44–8.88 M BA. The regeneration capacity of nodules is higher than that of direct regeneration or callus. Maximum regeneration was obtained from culture medium containing 0.54 M NAA and 0.44 M BA, where shoots could be observed as early as within 2 weeks. Many shoots formed roots in the same medium in which they were regenerated after 10 subcultures, but the best rooting occurred in medium containing 0.54 M NAA and 0.44 M BA. Rooted plantlets ofA. comosus Merr. could be routinely produced at 6-week intervals.Abbreviations NAA naphthaleneacetic acid - BA 6-benzylaminopurine     

Transient state characteristics of adaptation to changes in light conditions for the cyanobacterium Oscillatoria agardhii

Transitions in growth irradiance level from 92 to 7 Em^-2 s^-1 and vice versa caused changes in the pigment contents and photosynthesis of Oscillatoria agardhii. The changes in chlorophyll a and C-phycocyanin contents during the transition from high to low irradiance (HL) were reflected in photosynthetic parameters. In the LH transition light utilization efficiencies of the cells changed faster than pigment contents. This appeared to be related to the lowering of light utilization efficiencies of photosynthesis. As a possible explanation it was hypothesized that excess photosynthate production led to feed back inhibition of photosynthesis. Time-scales of changes in the maximal rate of O₂ evolution were discussed as changes in the number of reaction centers of photosystem II in relation to photosynthetic electron transport. Parameters that were subject to change during irradiance transitions obeyed first order kinetics, but hysteresis occurred when comparing HL with LH transients. Interpretation of first order kinetic analysis was discussed in terms of adaptive response vs changes in growth rate.Non-standard abbreviations Chla chlorophyll a - CPC C-phycocyanin - PS II photosystem II - PS I photosystem I - RC II reaction center of photosystem II - P photosynthetic O₂-evolution - I irradiance, Em^-2 s^-1 - light utilization efficiency of cells, mmol O₂·mg dry wt^-1·h^-1/Em^-2 s^-1 - light utilization efficiency of photosynthetic apparatus, mol O₂·mol Chla ^-1·h^-1/Em^-2 s^-1 - P_max maximal rate of O₂ evolution by cells, mol O₂·mg dry wt^-1·h^-1 - P_max maximal rate of O₂ evolution by photosynthetic apparatus, mol O₂·mol·Chla ^-1·h^-1 - LL low light, E m^-2 s^-1 - HL high light, E m^-2 s^-1 - LH low to high light transition - HL high to low light transition - k specific rate of adaptation, h^-1 - specific growth rate, h^-1 - Q pool size of cell constituent, mol·mg dry wt^-1 - q net synthesis rate of cell constituent, mol·mg dry wt^-1·h^-1     

The effect of monoterpenes on astaxanthin production by a mutant ofPhaffia rhodozyma

Summary The total pigment and astaxanthin content ofPhaffia rhodozyma increased with increasing concentrations -pinene up to 500 l -pinene/l. Above this concentration the total pigment and astaxanthin content as well as the biomass production decreased. The addition of 500 l -pinene/l increased the total pigment content from 1652 g/g to 2201 g/g and the astaxanthin content from 1554 g/g to 1883 g/g. A sharp decrease in maximum specific growth rate occurred above 150 l -pinene/l.     

The detection and characterization of bacteria-sized protists in “Protist-free” filtrates and their potential impact on experimental marine ecology

Nuclepore filters of 0.6–1.0m pore size have been used to prepare protist-free water for a number of studies in microbial ecology. This procedure has been called into question by a recent study claiming that a significant portion of bacterial loss in filtrates could be due to uncharacterized predators passing through 0.6m filters. We were unable to directly observe protists in 0.6m filtrates using phase contrast, epifluorescence, or transmission electron microscopy. Using the culture techniques of rice grain enrichment and most probable number, however, we were able to observe and quantify several species of bacterivorous nanoflagellates that developed not only in 0.6m, but also in 0.4m seawater filtrates. The ability of predacious nanoflagellates to squeeze through bacteria-sized pores questions studies of bacterial production and chemical cycling that have assumed protist-free filtrates.     

Somatic embryogenesis in cultured mature zygotic embryos of Abies balsamea

Embryo suspensor masses (ESMs) were induced by culture of isolated mature zygotic embryos of balsam fir [Abies balsamea (Mill.)] on media containing 10 M cytokinin [6-(--dimethylallylamino)purine (2iP), 6-benzyladenine (BA), or thidiazuron (TDZ)]. Once induced, ESMs proliferated on media containing 2iP, BA or TDZ (10 M) or on 4.5 M BA in combination with 10 M naphthyl-1-acetic acid. When ESMs were transferred to media containing 5–80 M abscisic acid, cotyledonary-stage embryos were formed. Embryos were readily germinated on medium lacking growth regulators.Abbreviations ABA abscisic acid - BA 6-benzyladenine - ESM embryo-suspensor mass - 2iP 6-(--dimethylallylamino)purine - NAA naphthyl-1-acetic acid - TDZ N-phenyl-N-1,2,3-thiadiazol-5-yl urea (thidiazuron)     

The effects of Tunicamycin and 2-deoxy-D-glucose on the development ofXenopus laevis embryos

Summary Tunicamycin and 2-deoxy-D-glucose were applied toXenopus laevis embryos in the first cleavage furrow, blastula and early gastrula stages. No effect was observed with 2-deoxy-D-glucose up to the concentration 0.1 M. The effect of Tunicamycin is dose- and stage-dependent. At the concentration of 5 g/ml cleaving embryos are arrested at the onset of gastrulation and their cells exhibit decreased intercellular adhesivity, while embryos treated in the blastula and early gastrula stages may develop up to the late neurula and tail-bud stage, respectively. Higher concentrations (up to 20 g/ml) drastically affect cleavage. Concentrations of 4 to 1 g/ml allow embryos to develop up to more advanced stages; however, developmental defects are the rule. Concentrations of less than 1 g/ml do not affect development.