Light energy supply in plate-type and light diffusing optical fiber bioreactors

The light distribution profiles of plate-type photobioreactors were investigated. Light reaching individual channels of a plate module is dependent on the orientation of the module to the sun, the position of the channel within a plate and the position of the plate. The highest incident radiation was measured at the south oriented side of the first channel of the front plate. The light intensity decreased from top to ground channels. Different types of light diffusing optical fibers (LDOF) were characterized with respect to their applicability in photobioreactor systems.     

Maintenance of lymphocyte surface Ig by mitogen stimulation in vitro.

In 4 to 24 hr cultures of rabbit lymphoid cells in medium supplemented with autologous serum, most B cells lost their surface Ig as assayed by rosette formation with anti-Ig antibody-coated erythrocytes. This loss was prevented by adding selected mitogens such as streptococcal mitogen (SM), lipopolysaccharide, and concanavalin A or by supplementing the medium with fetal calf serum. When SM was added at various times to the cultures (1, 2, 3, and 4 hr), it was effective in maintaining the approximate level of Ig-bearing cells present at the time of its addition but was ineffective in restoring the level of Ig-bearing cells present at the time the cultures were intiated. Very small, submitogenic doses of SM were sufficient to maintain the level of Ig-bearing cells. The data suggest that lymphocytes require continuous stimulation to maintain their surface receptors.     

Alteration of Cre recombinase site specificity by substrate-linked protein evolution.

Directed molecular evolution was applied to generate Cre recombinase variants that recognize a new DNA target sequence. Cre was adapted in a three-stage strategy to evolve recombinases to specifically recombine the new site. This complex multicycle task was made feasible by an improved directed-evolution procedure that relies on placing the recombination substrate next to the recombinase coding region. Consequently, those DNA molecules carrying the coding region for a successful recombinase are physically marked by the action of that recombinase on the linked substrate and are easily retrieved from a large background of unsuccessful candidates by PCR amplification. We term this procedure substrate-linked protein evolution (SLiPE). The method should facilitate the development of new recombinases and other DNA-modifying enzymes for applications in genetic engineering, functional genomics, and gene therapy.     

The Nop60B gene of Drosophila encodes an essential nucleolar protein that functions in yeast

The Cbf5 protein of Saccharomyces cerevisiae was originally identified as a low-affinity centromeric DNA-binding protein, and cbf5 mutants have a defect in rRNA synthesis. A closely related protein from mammals, NAP57, is a nucleolar protein that coimmunoprecipitates with the nucleolar phosphoprotein Nopp140. To study the function of this protein family in a higher eukaryote that is amenable to genetic approaches, the gene encoding a Drosophilamelanogaster homolog, Nop60B, was identified. The predicted Drosophila protein shares a high degree of sequence identity over a 380-residue region with both the mammalian and yeast proteins, and shares several conserved motifs with the prokaryotic tRNA pseudouridine 55 synthases. Nop60B RNA is found at high levels in nurse cells and in the oocyte, and is present throughout development. Nop60B protein is localized primarily to the nucleolus of interphase cells, and is absent from the chromosomes during mitosis. Nop60B mutants were generated and shown to be homozygous lethal. The Drosophila gene can rescue the lethal phenotype of yeast cbf5 mutations, showing that the function of this protein has been conserved from yeast to Drosophila. Received: 23 February 1998 / Accepted: 17 June 1998     

Aufnahme von Trypanblau und Ferritin in die Blasenzellen des Bindegewebes von Helix pomatia und Cepaea nemoralis (Stylommatophora,Pulmonata)

Zusammenfassung Untersuchungen des Bindegewebes der stylommatophoren Pulmonaten Helix pomatia and Cepaea nemoralis zeigen, daß die Blasenzellen des Bindegewebes befähigt sind, Substanzen aus der Hämolymphe aufzunehmen. Licht- und elektronenmikroskopische Untersuchungen ausgewählter Bindegewebsbereiche, die in bestimmten Zeitintervallen nach der Injektion von Trypanblau oder Ferritin in die Körperhöhle präpariert wurden (Stufenuntersuchungen), ergaben, daß — mit Ausnahme einiger Blutzellen — ausschließlich die Blasenzellen die injizierten Substanzen aufgenommen hatten. Weder andere Bindegewebszellen noch die Zellen von Organen (u.a. Gonaden, Schlundringganglien), die von Bindegewebe umgeben werden, enthielten diese Substanzen oder hatten sie akkumuliert. Die elektronenmikroskopischen Aufnahmen zeigen, daß die Aufnahme von Ferritin in die Blasenzellen wahrscheinlich durch Pinocytose erfolgt.

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Uptake of trypan blue and ferritin into the globular cells of the connective tissue of Helix pomatia and Cepaea nemoralis (Stylommatophora, Pulmonata)

Summary Investigations of the connective tissue of the stylommatophoran pulmonates Helix pomatia and Cepaea nemoralis have demonstrated, that so-called globular cells have the capability for the uptake of substances out of the hemolymph. Light- and electron-microscopic investigations of pieces of connective tissues fixed at different intervals after the injection of Trypane Blue or Ferritin into the cavity of the body give striking evidence for the uptake of these substances exclusively into the globular cells (with the exception of some blood cells). Neither other connective tissue cells nor cells of the organs (e.g. gonads, central nervous ganglions) surrounded by connective tissue incorporate or accumulate the injected substances. The uptake of Ferritin into the cytoplasm of the globular cells, normally filled with a high amount of glycogen, takes place by pinocytosis.

     

A Bacillus megaterium Plasmid System for the Production, Export, and One-Step Purification of Affinity-Tagged Heterologous Levansucrase from Growth Medium

A multiple vector system for the production and export of recombinant affinity-tagged proteins in Bacillus megaterium was developed. Up to 1 mg/liter of a His₆-tagged or Strep-tagged Lactobacillus reuteri levansucrase was directed into the growth medium, using the B. megaterium esterase LipA signal peptide, and recovered by one-step affinity chromatography.