Attachment and multiplication,morphology and protein production of human fetal primary liver cells cultured in hormonally defined media

In Vitro Cellular &; Developmental Biology - Plant -     

Studies on the System Regulating Proton Movement across the Chloroplast Envelope : Effects of ATPase Inhibitors, Mg, and an Amine Anesthetic on Stromal pH and Photosynthesis

Studies were undertaken to further characterize the spinach (Spinacea oleracea) chloroplast envelope system, which facilitates H⁺ movement into and out of the stroma, and, hence, modulates photosynthetic activity by regulating stromal pH. It was demonstrated that high envelope-bound Mg²⁺ causes stromal acidification and photosynthetic inhibition. High envelope-bound Mg²⁺ was also found to necessitate the activity of a digitoxinand oligomycin-sensitive ATPase for the maintenance of high stromal pH and photosynthesis in the illuminated chloroplast. In chloroplasts that had high envelope Mg²⁺ and inhibited envelope ATPase activity, 2-(diethylamino)-N-(2,6-dimethylphenyl)acetamide was found to raise stromal pH and stimulate photosynthesis. 2-(Diethylamino)-N-(2,6-dimethylphenyl)acetamide is an amine anesthetic that is known to act as a monovalent cation channel blocker in mammalian systems. We postulate that the system regulating cation and H⁺ fluxes across the plastid envelope includes a monovalent cation channel in the envelope, some degree of (envelope-bound Mg²⁺ modulated) H⁺ flux linked to monovalent cation antiport, and ATPase-dependent H⁺ efflux.     

Interannual variability of phytoplankton productivity and related parameters in Lake Constance: no response to decreased phosphorus loading?

In meso-eutrophic Lake Constance (Germany-Austria-Switzerland),phytoplankton bioraass, pigments and water transparency, aswell as primary productivity, have been followed between 1980and 1989. During this period, municipal phosphorus loading declinedsignificantly. Since 1981, soluble reactive phosphorus (SRP)concentrations during deep lake mixing have decreased from 3.0to currently 1 6 mmol m^–3 at a rate of 7% year^–1.Nitrate concentrations, by contrast, continued to rise. Duringthe period of maximum phosphorus loading, flushing through theoutlet and sedimentation were about equally important sinksof phosphorus from the euphotic zone. Recently, however, sedimentationand subsequent burial of P in the bottom deposits contributedabout three-quarters to the overall P-losses from the systemMain reasons for this shift are unchanged settling fluxes ofphosphorus out of the euphotic zone and decreasing concentrationsof total phosphorus in the water. Only during spring, do concentrations of soluble reactive phosphoruswithin the euphotic zone decrease in proportion to the formationof particulate organic matter. Later during the season, euphoticSRP concentrations continue to be low but are no longer matchedby high plankton biomass because phosphorus is efficiently removedby settling of particles In spite of the observed dramatic decreasein phosphorus loading since 1980, chlorophyll concentrationsand water transparency, as well as annual phytoplankton productivity(300 g C m^–2), have not shown a consistent downward trend.However, the intensity of phosphorus regeneration within theeuphoric zone, which can be used as a measure of the degreeof nutrient limitation, is likely to have increased significantlyThe most probable explanation for the insensitivity of importanttrophic state indicators to reduced nutrient loading is that,in Lake Constance, biomass accumulation to a greater extentis controlled by losses, mainly grazing by zooplankton and sedimentation,than by primary resources. This is concluded from the observationthat phytoplankton biomass always falls far short of the nutrient-dependentcarrying capacity of the system.     

Internal seiches in Lake Constance: influence on plankton abundance at a fixed sampling site

During thermal stratification, pronounced internal seiches occurin Lake Constance with periods of 4–6 days The amplitudesreach 12 m at the sampling site in berlinger See (northwesternpart of Lake Constance). Seiches change the thickness of thewarm and generally biologically rich epilimnion and, thus, alsothe areal abundance of planktonic organisms at a fixed samplingsite. The potential impact of seiche-dnven changes of epilimneticthickness on observed plankton abundance was calculated usingcontinuously recorded temperature profiles and weekly verticalprofiles of plankton biomass. Observed plankton biomass wasrecalculated by taking into account the effect of changing layerthickness in order to give a more realistic picture of biomasschanges caused by waxing and waning of populations Our calculationsimply that changes of strata thickness do not mask the generalseasonal trend in population dynamics (e g. spring bloom andclear water phase), estimates of average yearly standing stockare not significantly affected if sampling is done at leastweekly. However, changes of strata thickness can alter arealplankton abundance at the sampling site by a factor of 2 within2 days During pronounced seiches, areal abundance of phytoplankton,which generally exhibit a stronger vertical gradient than-mostother plankton, may be changed by a factor of 3–4 withinhours Hence, at our sampling site, the impact of changes instrata thickness cannot be ignored for detailed analysis ofpopulation dynamics of autotrophs involving comparisons betweensingle observations     

High-level expression of a tobacco chitinase gene in Nicotiana sylvestris. Susceptibility of transgenic plants to Cercospora nicotianae infection

Endochitinases (E.C. 3.2.14, chitinase) are believed to be important in the biochemical defense of plants against chitin-containing fungal pathogens. We introduced a gene for class I (basic) tobacco chitinase regulated by Cauliflower Mosaic Virus 35S-RNA expression signals into Nicotiana sylvestris. The gene was expressed to give mature, enzymatically active chitinase targeted to the intracellular compartment of leaves. Most transformants accumulated extremely high levels of chitinase-up to 120-fold that of non-transformed plants in comparable tissues. Unexpectedly, some transformants exhibited chitinase levels lower than in non-transformed plants suggesting that the transgene inhibited expression of the homologous host gene. Progeny tests indicate this effect is not permanent. High levels of chitinase in transformants did not substantially increase resistance to the chitin-containing fungus Cercospora nicotiana, which causes Frog Eye disease. Therefore class I chitinase does not appear to be the limiting factor in the defense reaction to this pathogen.     

Cryopreservation of Digitalis lanata Ehrh. cell cultures: Preculture and freeze tolerance

Cryopreservation experiments were performed with Digitalis lanata cell cultures. The main stress was laid on the behaviour of the cells during the preculture period and the capacity of various preculture additives to induce freeze tolerance. The following compounds were used as preculture additives: trehalose, mannitol, sucrose, melibiose, proline, and sorbitol. They are listed in the order of their respective efficiency. Using trehalose, high post-thaw viability rates were achieved and the cells resumed growth after a short lag period. Melibiose was used as a preculture additive for the first time. Its suitability was in the range of that of sucrose. Proline and sorbitol were not able to induce freeze tolerance in Digitalis cells. Cell viability showed a considerable decrease at the beginning of the preculture period. This reduction was found to be transient in the presence of trehalose, mannitol, sucrose, and melibiose. The damaging effects of proline and sorbitol were too severe to be compensated for by the cells. The PAL activity increased markedly in the presence of proline, whereas the trehalose-treated and the control cells behaved nearly identical to one another.     

Ultrastructure of the approximately 26S complex containing the approximately 20S cylinder particle (multicatalytic proteinase/proteasome).

We have isolated a large protein complex of approximately 26S from Xenopus laevis oocytes and eggs which is composed of the approximately 20S cylinder particle (multicatalytic proteinase/proteasome) and additional proteinaceous components. In its polypeptide composition and sedimentation coefficient this approximately 26S complex closely resembles the 26S ubiquitin-dependent protease, a high molecular weight multienzyme complex recently described in the literature. Specific antibodies directed against a single subunit of the approximately 20S cylinder particle retain, on affinity columns, the large approximately 26S complex, and on sucrose gradients up to approximately 50% of the approximately 20S cylinder particles present in oocyte extracts sedimented with approximately 26S, suggesting that a large proportion of the approximately 20S particles exists in the cell as a component of the approximately 26S complex. Electron microscopy reveals the approximately 26S complex to be a symmetrical elongated macromolecular assembly of at least three protein particles. The central core of the complex is formed by the approximately 20S cylinder particle to which two other large components are attached at the ends, yielding a dumbbell-shaped complex of approximately 40 nm in length. Dissociation of the approximately 26S complexes releases in addition to approximately 20S cylinder particles a novel type of a disc-shaped particle of approximately 15 nm diameter which may represent the attached components or subcomplexes of them. Based on its structural and biochemical properties we postulate that the approximately 26S complex identified here is identical to the ubiquitin-dependent protease.     

Murine erythrocyte ankyrin cDNA: highly conserved regions of the regulatory domain

Ankyrin is an essential link between cytoskeletal proteins, such as spectrin, and membrane bound proteins, such as protein 3, the erythrocyte anion exchanger. Although the amino acid structure of human ankyrin is known, the functional regions have been only partially defined. Sequence comparisons between mouse and human ankyrin offer one mechanism of identifying highly conserved regions that probably have functional significance. We report the isolation and sequencing of a series of overlapping murine erythroid ankyrin (Ank-1) cDNAs from spleen and reticulocyte libraries (total span 6238 bp) and identify potentially important regions of murine-human reticulocyte ankyrin homology. Comparison of the predicted peptide sequences of mouse and human erythroid ankyrins shows that these ankyrins are highly conserved in both the N-terminal, protein 3 binding domain (96% amino acid identity) and in the central spectrin-binding domain (97% identity), but differ in the C-terminal regulatory domain (79% identity). However, the C-terminal regulatory domain contains two regions of peptide sequence that are perfectly conserved. We postulate these regions are important in the regulatory functions of this domain.