Nitrogen-flow in the rotifer Brachionus rotundiformis and its significance in mass cultures

The nitrogen budget in the rotifer Brachionus rotundiformis wasmeasured by the stable-isotope technique. The budget was estimatedusing the difference in the turnover time between egestion andexcretion. The rotifer was fed on the algae Nannochloropsiswhich was labeled with ¹⁵N as a tracer. The turnover time ofegestion and excretion were 20 min and 2.5 hours, respectively. Where77% of the ingested nitrogen was egested, and of the assimilated23%, 18% were devoted to growth and 5% to excretion.As for the unassimilated nitrogen egested as faeces, it recycled tothe rotifer through bacteriovory. When the algae provided as foodwere almost fully consumed, bacteriovory became dominant. Thethreshold occurred when the concentration of algae in the culture wasbetween 1.5 and 0.5 million cells of Nannochloropsis per ml. Ina chemostat operated with un-limited food condition, bacterialnitrogen corresponding to 20% of algal feeding, was consumed by therotifer.In a semi-continuous mass culture where food condition was limited,bacteriovory was more effective in supporting the rotiferreproduction. It contributed to the extremely high nitrogen recoveryfrom the provided foods (algae and oil-yeast) to the harvestedrotifers. The rapid and large nitrogen outflow from rotifersaccelerated the propagation of edible bacteria and can explain thestrange paradox observed in the culture; daily supply of foods didnot cover the sum of growth and excretion.It is not too exaggerated to state that the rotifer mass culture issupported by bacteria. The future strategy for maintenance of masscultures should consider this aspect.     

The Structure and Characterization of the Surface Protein Layer of a Comamonas-Like Organism

The regular surface layer of a strain of a Comamonas-like organism was examined by electron microscopy. The surface layer protein was easily extracted from the cell surface by a 2.5 M solution of lithium chloride. The protein subunit has a molecular size of 32,000 daltons, but usually forms a large aggregate of more than 1,200,000 daltons. In the extract it formed a regular array of p4 symmetry and was observed to be intimately associated with fragments of lipopolysaccharide. The size of a subunit determined by the negative staining method and the image processing method measured 5.2 × 6.4 nm (width and length), was arranged in a cobblestone-like pattern, and was located in a lattice space measuring 13.0 nm square.     

Biochemical studies of rat liver Golgi apparatus. I. Isolation and preliminary characterization.

A method is described for the isolation of morphologically well-preserved Golgi apparatus from rat liver. The method is essentially the same as that of Morré et al. (Morré, D.J., Hamilton, R.L., Mollenhauser, H.H., Mahley, R.W., Cunningham, W.P., Cheetham, R.D., & Lequire, V.S. (1970) J. Cell Biol. 44, 484-491) except that mild cell disruption is achieved by means of a stainless-steel sieve. The average recoveries of protein and galactosyltransferase in the isolated fraction are about 6 mg from 10 g of perfused liver and about 35% from the homogenate, respectively. The preparation is virtually free from succinate-cytochrome c reductase, glucose-6-phosphatase, acid phosphatase, and 5'-nucleotidase. The Golgi fraction as well as its vesicular fragments is homogeneous upon isopycnic centrifugation in both sucrose and dextran density gradients. Their buoyant densities in sucrose are significantly higher than those in dextran, indicating that both forms of the organelle are closed systems which are impermeable to macromolecules. The galactosyltransferase activity of a freshly prepared Golgi fraction, measured with ovalbumin as galactosyl acceptor, is activated 26-fold by the addition of Triton X-100, whereas those of homogenized, sonicated, and aged preparations are only activated 2- to 4-fold.     

Effects of anions on ADP-stimulated aggregation of bovine blood platelets

ADP-stimulated aggregation of bovine blood platelets was observed in media containing isotonic potassium salts of various monovalent anions. The aggregation depended on the anion in the medium, the order of aggregation being Cl^?, Br^?>I^?>SCN^?, $\text{ClO}{}_4{}^{\mathrm{?}}$. After 30-min incubation, the extent of aggregation of platelets in Cl^? or Br^? medium was little changed, whereas, that in SCN^? or $\text{ClO}{}_4{}^{\mathrm{?}}$ medium was remarkably decreased. This anion dependency of aggregation may be due to change in the membrane potential.     

A Novel Glial Growth Inhibitory Factor, Gliostatin, Derived from Neurofibroma

Neurofibroma tissue was investigated for the presence of glial growth modulators that would suppress the proliferation of glial cells. A novel endogenous polypeptide inhibitor of proliferation and DNA synthesis in glial cells, gliostatin, was purified from the extracts of neurofibroma by a procedure comprising dye and anion-exchange column chromatography, and HPLC. A monoclonal antibody raised against partially purified gliostatin showed no cross-reactivity with known cytokines, but adsorbed the growth inhibitory activity of gliostatin and immunochemically visualized the putative gliostatin bands on western blot analyses. Although the product showed an apparent M(r) of 100,000 accompanied by an inhibitory activity on gel filtration column chromatography, it migrated at a lower apparent M(r) of 50,000 under the reducing conditions on western blotting, indicating that a homodimeric structure of native gliostatin consisted of 50-kDa subcomponents. Gliostatin was a potent growth inhibitor acting at nanomolar concentrations against all glial tumor cells and glia maturation factor-stimulated astroblasts, but not neuronal cells.     

Improved culture conditions for somatic embryogenesis from Asparagus officinalis L. using an aseptic ventilative filter

Summary Calli were induced from the crown of seedlings or lateral bud of young spears of Asparagus officinalis L. on Linsmaier and Skoog's (LS) solid-medium supplemented with 5 M 2,4-dichlorophenoxyacetic acid (2,4-D). Embryogenic callus was selected from induced calli and proliferated in LS liquid medium supplemented with 5 M 2,4-D. Non-vitrified somatic embryos were formed and efficiently developed into club-shaped embryos in LS hormone-free medium with 1 % gelrite in a culture vessel capped with an aseptic ventilative filter. Non-vitrified club-shaped embryos developed into normal plants when transferred to half-strength LS medium without hormones, and 0.8 % agar. Carbon dioxide concentration and moisture content inside the culture vessels were measured, and their effect on embryo development is discussed.