Regeneration from long-term cell suspension cultures of tepary bean (Phaseolus acutifolius)

Plant regeneration has been achieved from long-term cell suspension cultures established from leaf derived callus of tepary bean (Phaseolus acutifolius). The proportion of densely cytoplasmic cells in suspension culture increased when cultured in the L-6 medium with 54 M NAA and 2 M KN. Filtration of the cells at each of five consecutive subcultures resulted in the isolation of a plant regenerating cell line (TB 686), which is being maintained in L-6 medium with 4.5 M 2,4-D and 2.3 M zeatin. Differentiated green cell aggregates were obtained when cells from maintenance medium were transferred to the same medium with 10 M BA. Embryo-like structures developed from these aggregates on L-6 medium with 2.3 M zeatin, 0.69 M GA₃ and 1.5 M NAA. Plantlets regenerated from these structures when they were cultured on L-6 medium with 7.0 M NAA and 1.0 M KN. Plant regeneration from the cell line remained relatively constant for 270 days. Regenerated plants were grown to maturity in the greenhouse.Abbreviations BA Benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - GA₃ Gibberellic acid - IPA Isopentenyladenine - KN Kinetin - NAA Naphthaleneacetic acid - AA Amino acid medium (Toriyama and Hinita, 1985) The research was sponsored by United States Agency for International Development, Washington D.C., Cooperative Agreement DAN-4137-A-00-4053-00     

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     

Contribution of methanol to the production of methane and its <Superscript>13</Superscript>C-isotopic signature in anoxic rice field soil

Conversion of methanol to CH₄ has a large isotope effect so that a small contribution of methanol-dependent CH₄ production may decrease the ¹³CH₄ of total CH₄ production. Therefore, we investigated the role of methanol for CH₄ production. Methanol was not detectable above 10 M in anoxic methanogenic rice field soil. Nevertheless, addition of ¹³C-labeled methanol (99% enriched) resulted in immediate accumulation of ¹³CH₄. Addition of 0.1 M ¹³C-methanol resulted in increase of the ¹³CH₄ from –47 to –6 within 2 h, followed by a slow decrease. Addition of 1 M ¹³C-methanol increased ¹³CH₄ to +500 within 4 h, whereas 10 M increased ¹³CH₄ to +2500 and continued to increase. These results indicate that the methanol concentrations in situ, which diluted the ¹³C-methanol added, were 0.1 M and that the turnover of methanol contributed only about 2% to total CH₄ production at 0.1 M. However, contribution increased up to 5 and 17% when 1 and 10 M methanol were added, respectively. Anoxic rice soil that was incubated at different temperatures between 10 and 37 °C exhibited maximally 2–6% methanol-dependent methanogenesis about 1–2 h after addition of 1 M ¹³C-methanol. Only at 50 °C, contribution of methanol to CH₄ production reached a maximum of 10%. After longer (7–10 h) incubation, however, contribution generally was only 2–4%. Methanol accumulated in the soil when CH₄ production was inhibited by chloroform. However, the accumulated methanol accounted for only up to 0.7 and 1.2% of total CH₄ production at 37 and 50 °C, respectively. Collectively, our results show that methanol-dependent methanogenesis was operating in anoxic rice field soil but contributed only marginally to total CH₄ production and the isotope effect observed at both low and high temperature.     

Plant regeneration via somatic embryogenesis in Styrian pumpkin: cytological and biochemical investigations

Somatic embryo formation was induced from cotyledon explants of Styrian pumpkin (Cucurbita pepo L. subsp. pepo var. styriaca Greb.) by using a solid MS medium supplemented with 16.11M NAA and 4.44M BA or 26.85M NAA and 13.32M BA. The callus proliferation was more efficient on medium supplemented with 26.85M NAA and 13.32M BA. In contrast, the embryogenic response was higher on medium with lower concentrations of growth regulators (16.11M NAA and 4.44M BA). The time needed for embryo induction did not depend on medium composition. Embryos in globular stage were transferred to three different maturation media, containing 2.89M GA₃ in combination with 0.54M NAA, 11.42M IAA and growth regulator-free medium. The germination rate was the highest when embryos were cultured on medium with 11.42M IAA. Plantlets grown on this medium achieved maturity suitable for transplantation into soil within 9 to 10weeks. The regenerated plants were successfully transferred into field and developed fertile flowers and set fruits. Biochemical analysis showed significant lower total glutathione levels among in vitro grown plantlets compared to seedlings grown in soil. When the plantlets were transferred into soil, they reached a normal size within a month and the glutathione concentration was comparable to seed-derived plants at the same developmental stage. Transmission electron microscopy was used to investigate possible differences in the ultrastructure of cells from callus cultures, and leaf cells of regenerated and seed-derived plants. Differences in the ultrastructure were found within chloroplasts which contained only single thylakoids, large starch grains and small plastoglobuli in callus cells in comparison to leaf cells, which possessed a well developed thylakoid system, small starch grains and large plastoglobuli.     

Development of shoots and roots in anther-derived callus of Azadirachta indica A. Juss.—a medicinal tree

Callus originated in microsporangial wall layers and connective tissues of anthers containing uninucleate microspores on Nitsch's or Murashige and Skoog's medium supplemented with growth regulators. A higher percentage of cultures (43) produced callus on Nitsch's medium containing 10 M indole-3-acetic acid + 1 M 6-benzyladenine. After 13–15 weeks, green nodular structures and prominent roots developed in 25% of the cultures on Murashige and Skoog's medium + 10 M -naphthaleneacetic acid + 1 M kinetin. Multiple shoots were induced in this anther-derived callus when subcultured on Murashige and Skoog's medium augmented with 4.44 M 6-benzyladenine + 0.53 M -naphthaleneacetic acid along with 18.75 M polyvinylpyrrolidone. The excised shoots formed roots after subculturing on Murashige and Skoog's medium + 4.90 M indole-3-butyric acid + 18.75 M polyvinylpyrrolidone, thus developing complete plantlets. Examination of callusing anthers also revealed two- to multi-celled pollen masses with intact exine.Abbreviations BA 6-benzyladenine - CW coconut water - 2,4-d 2,4-dichlorophenoxyacetic acid - GA₃ gibberellic acid - HCl hydrochloric acid - IAA indole-3-acetic acid - IBA indole-3-butyric acid - KMnO₄ potassium permanganate - MS Murashige & Skoog's medium - NAA -naphthaleneacetic acid - NB Nitsch's medium - PVP polyvinylpyrrolidone     

Lead‐related effects on rat fibroblasts

Lead (Pb) is an environmental toxicant that can induce structural and functional abnormalities of multiple organ systems, including the central nervous and the immune systems. The aim of this study was to evaluate the effects of extracellular Pb supplementation on the cellular content of the metal and on the proliferation and the survival of normal rat fibroblasts.We found that the concentration of Pb in the culture medium was 0.060 M and the normal Pb concentration in rat fibroblasts was 3.1 ± 0.1 ng/10⁷ cells. Then we exposed the cells to increasing concentration of Pb (as Pb acetate) from 0.078–320 M. We observed a dosedependent inhibition of cell proliferation after 48 h, which was already apparent at a concentration of 0.312 M (p = 0.122) and became statistically significant for concentration higher than 0.625 M (p = 0.0003 at 5 M). Cell proliferation was completely compromised at 320 M Pb total inhibition of cell proliferation.To investigate the mechanisms of Pbmediated inhibition of cell proliferation, we evaluated the occurrence of apoptosis in the same cells and found that cytosolic DNA fragments, hallmark of apoptotic cell death, increased significantly at Pb concentrations from 2.5–10.0 M. The occurrence of apoptosis was also confirmed by FACS analysis which showed the appearance of a subdiploid peak at Pb concentrations from 5–20 M. The distribution of cells in the cell cycle showed a dosedependent accumulation of cells in the G₀/G₁ phase mainly compensated by a decrease in the percentage of cells in the S phase. In conclusion, our results demonstrate that induction of apoptosis contributes to the Pbinduced inhibition of cell proliferation in rat fibroblasts.     

Optimization of in vivo tumor targeting in SCID mice with divalent forms of 741F8 anti-c-erbB-2 single-chain Fv: effects of dose escalation and repeated i.v. administration

Single-chain Fv molecules in monovalent (sFv) and divalent [(sFv')₂] forms exhibit highly specific tumor targeting in mice as a result of their small size and rapid systemic clearance. As a consequence, there is a rapid reversal of the sFv blood/tumor gradient, resulting in diminished retention of sFv species in tumors. In this report we investigate two distinct strategies, dose escalation and repetitive intravenous (i.v.) dosing, aiming to increase the absolute selective retention of radiolabeled anti-c-erbB-2¹²⁵I-741F8 (sFv')₂ in c-erbB-2-overexpressing SK-OV-3 tumors in mice with severe combined immunodeficiency (SCID). A doseescalation strategy was applied to single i.v. injections of¹²⁵I-741F8 (sFv')₂. Doses from 50 g to 1000 g were administered without a significant decrease in tumor targeting or specificity. High doses resulted in large increases in the absolute retention of¹²⁵I-741F8 (sFv')₂. For example, raising the administered dose from 50 g to 1000 g increased the tumor retention 24 h after injection from 0.46 g/g to 9.5 g/g, and resulted in a net increase of greater than 9 /g. Over the same dose range, the liver retention rose from 0.06 g/g to 1 g/g, and resulted in a net increase of less than 1 g/g. The retention of 9.5 g/g in tumor 24 h fllowing the 1000-g dose of (sFv')₂ was comparable to that seen 24 h after a 50-g dose of¹²⁵I-741F8 IgG, indicating that the use of large doses of (sFv')₂ may partially offset their rapid clearance. When two doses were administered by i.v. injection 24 h apart, the specificity of delivery to tumor observed after the first dose was maintained following the second injection. Tumor retention of¹²⁵I-741F8 (sFv')₂ was 0.32 g/g at 24 h and 0.22 g/g at 48 h following a single injection of 20 g/g, while 0.04 g/ml and 0.03 g/ml were retained in blood at the same assay times. After a second 20-g injection at the 24-h assay time, tumor retention increased to 0.49 g/g, and blood retention was 0.06 g/ml, at the 48-h point. These results suggest that multiple high-dose administrations of radiolabeled 741F8 (sFv')₂ may lead to the selective tumor localization of therapeutic radiation doses.Supported by National Cancer Institute (NCI) National Cooperative Drug Discovery Group grant U01 CA51880, CA06927, an appropriation from the Commonwealth of Pennsylvania, and the Bernard A. and Rebecca S. Bernard Foundation     

Chlorophyll interference with phytochrome measurement

Measurements of phytochrome by (A_{725–815 nm}) were completely suppressed at chlorophyll concentrations of the order of 20–40 g g^-1 f.wt. in vivo and 37 g cm^-3 in vitro, and the readings were reduced by 50% at only 12 g cm^-3 in vitro. At these concentrations of chlorophyll in aqueous methanol, the loss of phytochrome signal in vitro appeared to be due to failure of phytochrome photoconversion rather than to interference with A measuremebt by chlorophyll fluorescence in the 125/815 nm measuring beam.Abbreviations Chl chlorophyll - P phytochrome - P_r and P_fr phytochrome in red absorbing and far-red absorbing forms     

The Effect of Phenylalanine on DOPA Synthesis in PC12 Cells

DOPA synthesis from phenylalanine was studied in PC12 cells incubated with m-hydroxybenzylhydrazine, to inhibit aromatic L-amino acid decarboxylase. DOPA synthesis rose with increasing concentrations of either phenylalanine or tyrosine; maximal rates (~55 pmol/min/mg protein for tyrosine; ~40 pmol/min/mg protein for phenylalanine) occurred at a medium concentration of ~10 M for either amino acid. The K_m for either amino acid was about 1 M (medium concentration). At tyrosine concentrations above 30 M, DOPA synthesis declined; inhibition was observed at higher concentrations for phenylalanine (300 M). These effects were most notable in the presence of 56 mM potassium. Measurements of intracellular phenylalanine and tyrosine suggested the K_m for either amino acid is 20–30 M; maximal synthesis occurred at 120–140 M. In the presence of both phenylalanine and tyrosine, DOPA synthesis was inhibited by phenylalanine only at a high medium concentration (1000 M), regardless of medium tyrosine concentration. The inhibition of DOPA synthesis by high medium tyrosine concentrations was antagonized by high medium phenylalanine concentrations (100, 1000 M). Together, the findings indicate that for PC12 cells, phenylalanine can be a significant substrate for tyrosine hydroxylase, is a relatively weak inhibitor of the enzyme, and at high concentrations can antagonize substrate inhibition by tyrosine.     

The contribution of size-fractionated plankton to biomass and primary production of phytoplankton in saline–alkaline ponds

Primary productivity, biomass and chlorophyll-a of size fractionated phytoplankton (<0.22 m, <3 m, <8 m, <10 m, <40 m, <64 m, <112 m and <200 m) were estimated in 6 ponds and 5 experimental enclosures. The results showed that the planktonic algae less than 10 m are important in the biomass and production of phytoplankton in saline–alkaline ponds. The production of size fractionated phytoplankton corresponding to <112 m, <10 m and <3 m in saline–alkaline ponds were 10.5 ± 6.6 , 8.6 ± 5.4 and 0.33 ± 0.1 mgC l^–1 d^–1, respectively. Mean community respiration rate was 1.80 ± 0.73, 1.69 ± 0.90 and 1.38 ± 1.12 mgC l^–1 d^–1, respectively. The average production of phytoplankton corresponding to micro- (10–112 m), nano- (3–10 m) and pico- (<3 m) were 1.61, 8.30 and 0.33 mgC l^–1 d^–1, respectively. The ratio of those to the total phytoplankton production was 15%, 79% and 3%, respectively. The mean respiration rate of the different size groups was 0.11, 0.31 and 1.38 mgC l^–1 d^–1; the ratio of those to total respiration of phytoplankton was 6%, 17% and 77%, respectively. The production of size-fractionated phytoplankton corresponding to <200 m, <10 m and <3 m in enclosures was 2.19 ± 1.63, 2.08 ± 1.75 and 0.22 ± 0.08 mgC l^–1 d^-1, respectively. Mean community respiration rates were 1.25 ± 1.55, 1.17 ± 1.42 and 0.47 ± 0.32 mgC l^–1 d^–1, respectively. The average production of phytoplankton corresponding to micro- (10–200 m), nano- (3–10 m) and pico- (<3 m) plankton was 0.11, 1.86 and 0.22 mgC l^–1 d^–1, respectively. The ratio of those to the total production of phytoplankton was 5%, 85% and 10%, respectively. The mean respiration rate of different size groups were 0.08, 0.72 and 0.46 mgC l^–1 d^–1, the ratio of those to total respiration of phytoplankton was 6%, 57% and 37%, respectively. The concentrations of chlorophyll-a of the phytoplankton in the corresponding size of micro- (10–112 m), nano- (3–10 m) and pico- (<3 m) plankton in the experimental ponds were 19.3, 98.2 and 11. 9 g l^–1, respectively. The ratio of those to the total chlorophyll-a was 15%, 76% and 9%, respectively. The concentrations of chlorophyll-a of phytoplankton micro- (10–200 m), nano- (3–10 m) and pico- (<3 m) plankton in enclosures were 1.7, 34.3 and 3.0 g l^–1, respectively. The ratio of those to the total chlorophyll-a was 4%, 88% and 8%, respectively.     

Effects of GABA antagonists,SR 95531 and bicuculline,on GABAA receptor-regulated chloride flux in rat cortical synaptoneurosomes

Synaptoneurosomes isolated from cerebral cortices of male Sprague-Dawley rats were used for studying GABA_A receptor-regulated chloride influx. The in vitro effects of GABA antagonists, SR 95531 (a pyridazinyl GABA derivative) and bicuculline, on pentobarbital-stimulated, muscimol-stimulated or flunitrazepam-enhanced, muscimol-stimulated chloride uptake were studied. The chloride uptake was determined at 30°C, for 5 sec. Pentobarbital and muscimol produced a maximal stimulation of chloride uptake in cortical synaptoneurosomes at 500 M and 50M, respectively. SR 95531 as well as bicuculline had no effect on the basal uptake of chloride. Whereas, SR 95531 (0.3–30 M) and bicuculline (0.1–100 M), when added 5 min before muscimol (50 M), produced a significant concentration-dependent inhibition of muscimol (50 M)-stimulated chloride uptake (IC₅₀ s of 0.89±0.11 M and 13.45±2.10M, respectively). In studies of the inhibitory effects of SR 95531 and bicuculline on pentobarbital (500 M)-stimulated chloride uptake, the IC₅₀ s were 0.81±0.12 M and 3.86±1.14 M, respectively. SR 95531 exhibited a more potent inhibitory effect than bicuculline on flunitrazepam-enhanced, muscimol-stimulated chloride uptake. The results revealed that SR 95531 has a more potent antagonistic effect than bicuculline on GABA_A-regulated chloride flux.     

Determination of copper, manganese and zinc in human liver

Autopsied liver tissue samples collected from 42 males and 31 females were analyzed for copper, manganese and zinc using atomic absorption spectrometry (AAS). With the exception of two liver samples for which the copper levels were determined to be 74.8 and 104.0 g/g (dry weight), hepatic copper concentrations were found to range from 1.7 to 32.4 g/g with a mean concentration of 14.2 g/g and standard deviation of 7.0 g/g. Manganese concentrations (with the exception of one sample having 12.9 g/g) ranged from 0.22 to 4.6 g/g with a mean of 2.26 ± 1.00 g/g. Hepatic zinc levels averaged 118.3 ± 44.4 g/g and ranged from 38.5 to 231.3 g/g. There were no apparent trends for the levels of any metals versus age nor were there any differences in average hepatic metal concentrations for males and females. © Rapid Science 1998.     

Hormones andCuscuta development: In vitro induction of haustoria by cytokinin and its inhibition by other hormones

Cytokinins induced haustoria formation in excised 10-mm segments ofCuscuta vine, the subapical 25-to-50-mm region being most responsive, producing a mean of 4–6 haustoria per segment. The order of effectiveness of cytokinins continuously applied (72 h) was 6-benzylaminopurine (BA) isopentenyladenine (iP) zeatin (Z). Ribosides of BA and Z were as effective as the bases, whereas riboside of iP ([9R]iP) was half as effective as iP. Haustoria induction was influenced by weather and seasonal conditions at the time of vine collection; materials obtained on warm, sunny days responded better than those obtained on rainy, cloudy, or cool days. Haustoria were induced equally well all around the segment, and no thigmostimulus was needed for induction. p ]A 10-min pulse of 100 M BA induced half as many haustoria as a 60-min pulse or continuous application of BA. White light inhibited haustoria induction elicited by a short (30-min) pulse of BA, whereas a longer (120-min) BA application overcame this light inhibition. Auxins (IAA or NAA, 1–10 M), gibberellin (GA₃, 1–10 M), ethylene (as ethrel, 10–100 M), and abscisic acid (ABA, 100 M) were individually inhibitory (60–80%) with respect to haustoria induction when given continuously with 50 M BA. A 60-min pulse of auxins (10 M), GA₃ (100 M), or ethrel (10 M), given at various time intervals during or after a 60-min pulse of 100 M BA, showed that inhibition was maximal (70–95%) between 4 and 16 h of BA application and negligible (GA₃) or much reduced (auxin, ethrel) at 20 h, indicating a commitment to haustoria formation by this time.     

Calpain-PKC Inter-Relations in Mouse Hippocampus: A Biochemical Approach

In previous studies, we isolated and identified a -calpain/PKC complex from rabbit skeletal muscle. Here, we have used specific purification procedures in order to study the interactions between -calpain and PKC in mouse hippocampus, a brain structure implicated in memory processes. We observed that -calpain and conventional PKCs (, II and ) are co-eluted after anion exchange chromatography. In contrast to our previous results obtained on skeletal muscle, -calpain and PKC isoenzymes were dissociated after gel filtration chromatography. Furthermore, -calpain induced the proteolytic conversion of PKC, II, and into PKM, II, and with a preferential hydrolysis of PKC, a specific isoenzyme of the nervous system. Although the -calpain/PKC interactions in the hippocampus are quite different from skeletal muscle, our results however, point out the functional importance of these inter-relations. Moreover, as PKC has been involved in the biochemical events underlying learning and memory, the preferential relationship between -calpain and PKC promotes the importance of the role that -calpain could play in the cellular mechanisms of memory formation.     

Plant regeneration from cell suspension cultures of Vigna aconitifolia

Plant regeneration has been achieved routinely from established cell suspension culture lines of Vigna aconitifolia (moth bean), a highly drought tolerant grain legume. The cultures originated from three-week-old leaf callus. Several media including MS, B₅, AA, SL, PCM, SH and L-6 were tested for their effects on cell growth. Maximum growth was observed in L-6 medium containing 44.5 M 2,4-D. After 6 to 8 weeks the suspensions were filtered through 500, 250, 125 and 60 m sieves, respectively, for four to five subcultures. An embryogenic cell line (VA-686) was obtained from the cell fraction collected below 250 m. The VA-686 cell line is being maintained on L-6 medium with 4.5 M 2,4-D and 2.3 M Zeatin. Somatic embryogenesis was induced by transferring the cells to L-6 medium with 4.6 M zeatin in which green cell clusters were produced. The somatic embryos developed from most of the cell clusters when plated on L-6 agar medium with 2.3 M BA.Plantlets were obtained from the embryos on L-6 medium with 10.0 M IBA. The regenerated plants were grown to maturity in the greenhouse.Abbreviations BA Benzyladenine - 2,4-D 2,4- dichlorophenoxyacetic acid - GA₃ Gibberellic acid - IBA Indole-3-butyric acid - IPA Isopentenyladenine - KN Kinetin - NAA Napthaleneacetic acid - AA Toriyama and Hinata, 1985 - SL Phillips and Collin, 1980 A project sponsored by United States Agency for International Development, Washington D.C.     

Sorbitol as a non-repressing carbon source for fed-batch fermentation of recombinant Pichia pastoris

Glycerol/methanol and sorbitol/methanol mixed-feed fermentation strategies for the production of recombinant proteins by Pichia pastoris were compared in order to examine sorbitol's potential as a carbon source. Although P. pastoris does have a lower cell yield on sorbitol than on glycerol, the specific rate of product formation is higher (60 g protein g^–1 dry wth for sorbitol/methanol, vs 45 g protein g^–1 dry wth for glycerol/methanol), resulting in comparable final recombinant expression levels. Importantly, the presence of residual sorbitol in the growth medium appears to be less repressive to the alcohol oxidase promoter in this organism, providing a more forgiving means of operating mixed-feed fed-batch recombinant P. pastoris fermentations.     

Effects of light on nitrate-limited Oscillatoria agardhii in chemostat cultures

The effects of the average light irradiance (I) on growth and nitrate uptake kinetics of the cyanobacterium Oscillatoria agardhii, in nitrate-limited chemostat cultures, were studied. Light was nonsaturating for I <9.4 Wm^–2, for all growth rates () studied. However, was throughout limited by the availability of nitrate. Under light-saturating conditions the kinetics of nitrate-limited growth could be adequately described by both the Monod and Droop equations. Under light-non-saturating conditions the internal nitrogen content (Q) was a function of both and I, for which new formulas were derived. The high uptake capacity (V _max) of nitrate-limited cells was independent of , but was significantly increased for cells growing at I <9.4 Wm^–2. The half-saturation constant for nitrate uptake (K _s ^u ) increased with increasing , but was independent of the prevailing light conditions. The effects of light during nitrate-limited growth were associated with the regulation in the nitrogen-containing pigments.The results reported herein have important consequences for the use of Q, K _s ^u and V _max values as indicators of nutrient-deficiency of natural populations.     

Der Entwicklungscyclus mit Sexualphase bei der marinen Diatomee Coscinodiscus asteromphalus

Zusammenfassung Die Kultur der großen marinen Diatomee Coscinodiscus asteromphalus wird beschrieben. Die Synchronisation der vegetativen Stadien aus dem Entwicklungscyclus mit Sexualphase wird durch Messung der Valvendurchmesser charakterisiert. Die Art entwickelt sich von Stadien mit 200 m Valvendurchmesser (V.-D.), die nicht sexuell induzierbar sind, zu Stadien mit 80–90 m V.-D. mit einem Optimum der Induzierbarkeit und weiter zu Stadien mit 55–60 m V.-D. Bei dieser Größe ist keine weitere mitotische Zellteilung mehr möglich. Entwicklungsstadien mit 200–190 m, 140–130 m und 100–90 m. V.-D. zeigen bei 24°C und bei 18°C die gleiche Generationszeit im mitotischen Entwicklungscyclus von 1 bzw. 0,6 Zellteilungen pro Tag. Der Valvendurchmesser verringert sich bei dieser Art um 1,5 m bei 24°C und 1,4 m bei 18°C während einer Zellteilung.

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The life cycle with sexual phase in the marine diatom Coscinodiscus asteromphalus I. Culture and synchronisation of developmental stages

Summary Culture-conditions for the large marine centric diatom Coscinodiscus asteromphalus are described. The cells grow in a defined medium in a light-dark regime of 14: 10 h. Synchronization of different stages of the sexual life cycle is characterized by measuring the valve diameter (v.d.) of the cells. The cells develop from stages with 200 m v. d. (not sexually inducible) to stages with 80–90 m v. d. (optimum for sexual induction), and further to stages with 55–60 m v. d., where no following mitotic cell division is possible. The length of the pervalvar axis does not change during this development. Different stages (200–190m, 140–130 m and 100–90 m v. d.) grow with the same doubling time during their mitotic life cycle: 1 cell division per day at 24° C and 0.6 cell divisions per day at 18°C. During one cell division the valve diameter of this species decreases by about 1.5m at 24°C and by 1.4 m at 18°C. Therefore, the development from stages with 200 m v.d. to stages with 60 m v. d. takes between 90 days at 24°C and 165 days at 18°C.

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Teile einer Habilitationsschrift der Naturwissenschaftlichen Fakultät der Universität Marburg (Lahn).     

Methylobacterium rhodesianum MB 126 possesses two acetoacetyl-CoA reductases

Two constitutive acetoacetyl-CoA (AcAc-CoA) reductases were purified from Methylobacterium rhodesianum MB 126, an NADPH-linked d(-)--hydroxybutyryl-CoA forming reductase (enzyme A) and an NADH-and NADPH-linked l(+)--hydroxybutyryl-CoA forming reductase (enzyme B). Enzyme A and B give apparent K _m values of 15 M and 30 M for AcAc-CoA, 18 M for NADPH and 30 M for NADH, respectively. They are inhibited by AcAc-CoA at concentrations higher than 25 M and 50 M, respectively. The contribution of the two reductases to poly--hydroxybutyrate synthesis is discussed.     

Different effects of inorganic and triethyl lead on growth and ultrastructure of lily pollen tubes

Summary Pollen tubes ofLilium longiflorum growingin vitro were treated for 1 h with inorganic lead (Pb) and with triethyl lead (TriEL) and studied by light and electron microscopy. Pb was considerably more toxic in relation to inhibition of pollen tube growth (EC₅₀=6 M Pb) than was TriEL (EC₅₀=60 M TriEL). On the other hand, at almost the entire concentration range tested (25-500 M) TriEL caused aberrant tubes and tube swellings. Pb did not cause tube swellings, even at highly growth-impairing concentrations. Pb (60 M) predominantly affected the ultrastructure of the growing cell walls without impairing the distribution of the cell organelles in the tube tips. In contrast, 50 and 100 M TriEL did not visibly influence cell wall ultrastructure but it severely damaged dictyosomes; 100 M TriEL also disturbed the original order of cell organelles in the tube tips. Cortical microtubules were selectively and completely destructed by TriEL at concentrations (50 M) where no effect on polar organization of the tube tips occurred but they remained unimpaired by 60 M Pb, indicating selective and effective interaction of TriEL with these cell organelles.Abbreviations EC⁵⁰ effective lead concentration causing 50% inhibition of pollen tube growth - MTs microtubules - Pb inorganic lead - TriAL trialkyl lead - TriEL triethyl lead