Anders Edström

AMINO ACID INCORPORATION IN ISOLATED MAUTHNER NERVE FIBRE COMPONENTS

MOST information on the origin of proteins in the axoplasm is based on experiments with whole nerves. Certain difficulties in the interpretation of such experiments are due to the complex architecture of a nerve. In autoradiographic studies with tritiated amino acids on the other hand (DROZ and LEBLOND, 1963), the resolution may not be sufficient to permit a differentiation of e.g. axoplasm, myelin and Schwann cells. Difficulties such as these can be avoided with the use for analysis of isolated axons and myelin sheaths, uncontaminated by other tissue constituents. For this purpose the Mauthner neuron of the carpfish (Carassius carassius), from which clean fibre constituents can be isolated, provides a suitable system. The results to be presented suggest an active proximo-distal transport in the rostra1 region of the Mauthner axon of proteins synthesized in the perikaryon. In addition to data supporting this mechanism, evidence will be given for the presence of a coexisting local protein synthesis, the latter one taking place along the whole Mauthner nerve fibre both in axoplasm and surrounding myelin sheath.

THE RIBONUCLEIC ACID IN THE MAUTHNER NEURON OF THE GOLDFISH.

THE ribonucleic acid (RNA) in the Mauthner axon and myelin sheath of the goldfish (Curussius uuratus) (EDSTROM, EICHNER and EDSTROM, 1962) is of immediate interest in the study of the origin and function of the axoplasm. Further characterization of this RNA is desirable and has necessitated improved analytical procedures, to be described in the present paper. Results indicating quantitative gradients in the axon and its myelin sheath will be presented. The base composition of the RNA of the axon and myelin sheath has been found to be of a ribosomal type.

PROTEIN SYNTHESIS IN THE ISOLATED MAUTHNER NERVE FIBRE OF GOLDFISH

Abstract— Mauthner nerve fibres isolated from the spinal cord of goldfish were incubated, in the presence of radioactive amino acids for varying periods of time. It was found that the Mauthner fibre synthesizes proteins in the absence of cell nuclei. Amino acid incorporation showed sensitivity to puromycin and to acetoxycycloheximide but resistance to chloramphenicol. Only slight inhibition was caused by actinomycin‐D. The contribution of the denuded axon to the total protein synthesis was about 30 per cent per unit length Mauthner fibre. The remaining activity was due to the myelin sheath compartment. Fractionation experiments showed that the incorporation in the sheath was due to components other than the myelin lamellae. The subcellular distribution of newly synthesized proteins in the isolated and incubated Mauthner fibre was compared to that found in the incubated spinal cord. The results strongly suggested the existence in the Mauthner fibre of a primary microsomal, rather than a mitochondrial, protein synthesizing system.

SEDIMENTATION ANALYSIS OF RIBONUCLEIC ACID EXTRACTED FROM ISOLATED MAUTHNER NERVE FIBRE COMPONENTS

Abstract— Segments of spinal cords from goldfish or from carp were incubated in vitro in the presence of RNA precursors for varying periods of time. Mauthner nerve fibres were isolated from the fresh unfixed tissue, or, for the separate analyses of axon and myelin sheath, from the fixed spinal cord.

EFFECT OF SPINAL CORD TRANSECTION ON THE BASE COMPOSITION AND CONTENT OF RNA IN THE MAUTHNER NERVE FIBRE OF THE GOLDFISH

AMONG the vertebrates, axonal and myelin sheath protoplasm, in a pure and uncontaminated form, is generally inaccessible to chemical investigation. An exception is provided by the Mauthner nerve fibre of the fish, the two components of which can be isolated and analysed separately for RNA with microchemical methods (J.-E. EDSTROM, EICHNER and A. EDSTROM, 1962; A. EDSTROM, 1964). The presence of RNA as defined by several criteria could be ascertained in both components. The reaction of the RNA in the nerve cell body to interruption of its long process has been studied. Microchemical investigation has made clear that the characteristic change is an increase in the RNA content (BRATTGARD, J.-E. EDSTROM and HYDBN, 1957; J.-E. EDSTROM, 1959). It has seemed natural to extend this work also to the axonal RNA (and that of the myelin sheath). The results which were obtained indicate that local metabolic changes of high molecular compounds are more important than is generally believed. Similar conclusions were reached with regard to axonal acetylcholinesterase in the studies of KOENIG and KOELLE (1961) and CLOUET and WAELSCH (1961).

INHIBITION OF PROTEIN SYNTHESIS IN MAUTHNER NERVE FIBRE COMPONENTS BY ACTINOMYCIN‐D

RECENTLY evidence of a local synthesis of acetylcholinesterase in the motor axons of the XIth cranial nerve root was provided by KOENIG (1965a). In previous work (EDSTROM, 1966) the existence of a local protein synthesis in the Mauthner axon as well as in the surrounding myelin sheath was demonstrated. It is desirable to know more about the nature of this synthesis, especially in view of the fact that it occurs far from the genome-containing nucleus. In particular it is desirable to know whether it is ultimately directed by DNA and, if so, if this dependence is due to the DNA of the nuclear containing cell body or not. Actinomycin-D has been shown to inhibit selectively the DNA dependent RNA synthesis in other systems (GOLDBERG, RABINOVITZ and REICH, 1962 ; STAEHELIN, WETTSTEIN and NOLL, 1963 ; TRAKATELLIS, AXELROD and MONTJAR, 1964). In the present work actinomycin-D had an inhibiting effect on the local amino acid incorporation in the Mauthner nerve fibre components, which suggests a local, ultimately DNA directed protein synthesis in the Mauthner nerve fibre. Furthermore, it was shown that this dependence is not due to the cell body of the Mauthner neuron.

Discipline and Creative Work — Designing Next Year’s Car Model

This chapter deals with the management of creative design work in large organisations. The focus of the chapter is on the complexity, for the individual, of navigating proposals through the creative process. A minor incident in a multi-million dollar, three-year project charged to bring out another year model of an existing car is chosen to illustrate how organisational embeddedness generates complexity.

Learning, innovation and IT-usage - a research approach to regional development

Regional clusters of companies are becoming an increasingly important focus of government industrial policy makers and researchers. A cluster is a network of companies in an industrial sector where suppliers, customers, consultants, etc. interact together with regional policymakers and universities. Sometimes the individual firms compete, and sometimes they collaborate. The delimited characteristics of a cluster to a regional area and an industrial sector, makes it possible to view the cluster as an arena or laboratory. The concept of regions as laboratories, which is the base for the present paper, does not have a policy orientation. Instead, it stresses the interactive and cooperative aspects, which emerge organically in a regional cluster. The paper presents the formation of a research arena in cooperation between the University College of Boras and the industry organization of Swedish mail order companies for studies of learning and innovations in IT usage within the cluster. The strategy to establish the arena, formulation of research questions and initial experiences are presented.