Carlsberg Foundation

The following exposition sets out to identify the basic theoretical and empirical building blocks for a general theory of self-regulation. It uses the Internet as an empirical basis since its global reach and technical characteristics create interdependencies between actors that transcend national boundaries and allow for non-governmental forms of regulation to emerge. The current wave of globalization increasingly creates global interdependencies that open avenues to new forms of self-regulation. A study of the Internet from this perspective provides us with the conceptual tools needed to interpret these developments and develop tools to direct regulatory policies more effectively. The first part of this exposition provides the theoretical building blocks by analyzing the concept of self-regulation. The second part provides empirical building blocks by analyzing the state of affairs of one of the most contested types of regulation on the Internet, its domain name system. The third part of the exposition integrates the findings of the first and second part of the inquiry and concludes by emphasizing the characteristics of the Internet and by accentuating the relevance of the Internet situation to the development of a general theory of self-regulation in a global context.

Paul Canart: Paleografia e codicologia greca: una rassegm bibliografica. (Littera antiqua, 7, Subsidia studiorum, 2.) Pp. 131. Vatican City: Scuola Vaticana di Paleografia, Diplomatica e Archivista, 1991. Paper. - Volume 42 Issue 2

The fission yeast Schizosaccharomyces pombe contains about 30% more RNA per unit protein when cultivated in a complex broth medium than in a chemically defined, peptide free medium. In cells growing on complex medium the rate of RNA synthesis can be reduced by an inhibitor peptide from the ciliated protozoan Tetrahymena pyriformis. There is no effect on protein synthesis, and the Tetrahymena peptide is without effect on yeast cells in a defined medium. Actinomycin D reduces both RNA and protein synthesis in cells growing on complex as well as defined medium, and the timing of the effect of Actinomycin D and Tetrahymena peptide differs, all suggesting different mechanisms of action of the two peptide inhibitors. In defined growth medium RNA synthesis can be stimulated by addition of unspecific small peptides. Stimulation of RNA synthesis has no effect on growth rate or cell division rate within the experimental period. We conclude that small peptides in the growth medium specifically stimulate the rate of RNA synthesis in Schizosaccharomyces pombe and that the Tetrahymena peptide inhibits the peptide-induced RNA synthesis.

Tetrahymena cells secrete a factor which inhibits RNA synthesis in vivo and in vitro. The factor is a relatively small peptide with a molecular weight between 300 and 1500 Daltons. Other, non-specific peptides in the broth medium or added to a chemically defined medium have a stimulatory effect on RNA synthesis in vivo and such peptides also stimulate the in vitro synthesis of RNA in a r-chromatin preparation. On the basis of these results we conclude that such extracellular small peptides compete with a specific factor which is part of the intracellular regulatory mechanism controlling the rate of RNA synthesis. The consequence of such competition is a high overproduction of ribosomal RNA in cells inoculated on peptide-rich broth media.

Schizosaccharomyces pombe grows and multiplies for many generations in the presence of chloramphenicol (CAP, 2 mg ml-1). CAP-grown cells exhibit nearly fully suppressed respiration, while fermentation occurs at the same rate as in untreated controls. The growth rate of the cultures is reduced in proportion to the diminished energy production, but the content of protein and bulk RNA per cell remain as in untreated cells. The effects of CAP are reversible. It is argued that CAP in S. pombe specifically inhibits mitochondrial protein synthesis without interfering with cytoplasmic protein synthesis. CAP-treated cultures can be division-synchronized either by a selection technique or by a controlled temperature regimen and the synchronous divisions studied after removal of CAP.

Previously, we found that a mutant strain of Tetrahymena pyriformis without food vacuoles failed to grow unless the nutrient media were richly supplemented with vitamins and trace metals. Here we show that calcium folinate alone can replace the extra vitamin supplementation. The mutant requires approximately 90-fold higher concentration of folinate than the wild-type cells to give similar growth responses in a chemically defined medium. We infer that the food vacuole is an important route of uptake for this vitamin in the wild-type cells. We found no difference between mutant and wild-type cells in their requirements for nicotinic acid, pantothenic acid, riboflavin-monophosphate, and pyridoxal. We infer that an extravacuolar route contributes importantly to uptake of these 4 compounds.

SYNOPSIS. Using continuous flow cultures based on the chemostat principle, we varied the cell generation times of the ciliate Tetrahymena pyriformis strain GL, from 4.9 to 22.2 hr and studied various parameters of the cell cycle at 28 C. These included: the duration of the periods required for oral morphogenesis, macronuclear division, cell division, G1 S, and G2. The size of individual cells was also measured.Independent of the growth rate, the period of oral morphogenesis occurred during the last 90 min of the cell cycle. In all cases macronuclear and cell divisions took place during the last part of these 90 min, and the final macronuclear separation occurred just before final cell separation. The S‐period increased slightly, while the G1 and G2 both increased in roughly the same relative proportion to the increasing generation times. Slowly growing cells (generation time 20.5 hr) were shorter but broader and somewhat larger in volume than quickly growing cells (generation time 4.9 hr).

The glycolytic activity of 3 different synchronous system in S. pombe was studied. Synchronous cultures were produced by a selection procedure, by cyclic heat treatment, or by cloning cells from an exponentially multiplying culture. In all experiments a complex medium with 3% glucose was used. The glycolytic activity was recorded with a gasometric method, the gradient diver. A single cell in exponential growth or a small number of synchronized cells were placed in ampulla divers in which the cells progressed undistrubed through a number of cycles. An ampulla diver is in principle a narrow pipette by which a single or a few cells are removed from the mother culture. It serves next as an axenic growth chamber and at the same time as a gasometer. The divers were placed in linear saline density gradients and the gaseous exchanges taking place in the divers resulted in migration of the divers. The migration rate is a measure of the glycolytic activity of the cells. Our results show that the glycolytic activity increases in a linear fashion between sucessive divisions. The rate of increase doubles at each division. This true in all 3 synchronous systems, and we take this as an indication that the cell cycles of heat-synchronized cells do not deviate seriously from the normal.

SYNOPSISThis report describes an electronic cell counter constructed for determining cell number in cultures of the ciliate, Tetrahymena pyriformis. The culture chamber has been equipped with a device which determines the number of cells per unit volume and records the number automatically. As cell multiplication is unaffected by the counting procedure the cells are returned to the culture. Furthermore, keeping the culture volume constant we have arranged a continuous flow of fresh nutrient medium through the culture chamber and thus established conditions under which cell multiplication has continued for months while determinations of cell concentrations have been recorded every 10 min. Since the culture volume has been small, ∼25 ml, growth studies utilizing this method require less than one liter of fresh medium per week in spite of the fast multiplication (9 generations per 24 hr) occurring in cultures of Tetrahymena pyriformis under optimal conditions.