Addition of dimethylsulfoxide at concentrations of 1% and 2% (vol/vol) to cells of mouse neuroblastoma clone NIE-115 in the confluent phase of growth resulted in the production of morphologicalfir differentiated cultures with extensive process formation. Cells maintained in 2% dimethylsulfoxide remained in a stable nondividing condition for periods of up to 4 weeks. A high degree of electrical excitability was found in these cells, but there was no clear correlation of this property with the level of induction of either acetylcholinesterase (acetylcholine hydrolase; EC 3.1.1.7) or tyrosine hydroxylase [L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating); EC 1.14.16.2]. In addition, intracellular levels of cyclic 3':5'-AMP were not elevated in fully morphologically and electrically differentiated cells. While cell division was markedly inhibited by 2% or higher concentrations of dimethylsulfoxide, at 1% growth continued at a somewhat slowed rate and such cultures exhibited enhanced process formation and electrical activity for a relatively short period. High concentrations (3% or 4%) of dimethylsulfoxide totally suppressed process formation and did not result in increased excitability, but cells maintained high resting potentials. The results suggest that the development of the excitable membrane in neuroblastoma cells maybe expressed independently of neurospecific enzyme induction, and does not require a sustained elevation of cyclic 3'i5'-AMP levels.Nerve cells are characterized by their unique morphological appearance, the possession of an excitable membrane, and a specialized biochemical machinery. In order to study the expression of specific neuronal properties during the maturation process it is necessary to obtain sufficient quantities of a relatively homogeneous differentiating population. Cloned cell lines isolated from the C-1300 mouse neuroblastoma may serve as a useful system for exploring certain aspects of nerve cell differentiation. The transition of a culture of neuroblastoma cells from the actively dividing state to the confluent one is characterized by the synthesis of various enzymes involved in neurotransmitter metabolism (1), an enhancement of electrical excitability (2, 22), and some degree of process formation. To achieve a further expression of these properties, cells have been treated with various agents such as aminopterin (3, 4) or dibutyryl cAMP (5-7).In the present study, we show that in the presence of dimethylsulfoxide (Me2SO) neuroblastoma cells will extend neurites and develop a highly excitable membrane. It appears that this method offers certain advantages over those most commonly used, especially in that cells appear to reach a higher level of electrical differentiation and can be maintained in this state for extended periods. In experiments where logarithmically growing cells were used, cultures were trypsinized before attaining confluency and replated in 60 mm dishes at a density of 1 X 105 cells per dish. Two days later, the medium was replaced w...

and 7 factors, we have synthesized five peptides that are homologous to the corresponding sequence from the porcine or rat carboxyl-terminal region. Binding studies with the synthetic peptides suggest that amino acid residues 434-440 of ,Btubulin are crucial for the interaction of MAP2 and 7 factors.

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Rabbit globin mRNA species containing poly(A) segments of different lengths were prepared by partial phosphorolysis of mRNA with Escherichia coli polynucleotide phosphorylase. By varying the salt concentration and the time of incubation of the phosphorolysis mixture, as well as performing oligo(dT)-cellulose chromatography at 22 "C and at 4 "C, globin mRNA preparations containing poly(A) segments of approximately 122, 95, 68, 39, 32,21, and 16 adenylate residues were obtained. It was found that the functional stability of the mRNA species containing 32 or more adenylate residues after injection into Xenopus luevis oocytes equaled that of the native globin mRNA. On the other hand, the functional stability of mRNA containing an average number of 21 adenylate residues was about 30% of the native mRNA, while that of mRNA containing 16 adenylate residues was as low as poly(A)-free globin mRNA.The existence of poly(A)-rich sequences at the 3'-end of most eukaryotic mRNAs is well established (for reviews see [l -31). The biological role of the poly(A) segment was the subject of many recent studies. Inhibition of post-transcriptional adenylation by the adenosine analogue cordycepin strongly reduces the flow of mRNA from the nucleus to the cytoplasm. This finding forms the basis for the suggestion that nuclear adenylation is an essential step in the biogenesis of mRNA or in its transport to the cytoplasm [4,5].Other findings, such as shortening of the poly(A) segment during the aging of mRNA [6,7] cytoplasmic adenylation [8,9], and the presence of a poly(A) segment in a viral message which is synthesized in the cytoplasm [lo], suggest an additional role for the poly(A) segment outside of the nucleus. Results reported from this and other laboratories have shown that the poly(A) segment of globin mRNA is not essential for its translation in cell-free systems [l 1 -161. However, preincubation in cell-free extracts decreases the template activity of poly(A)-free mRNA more than that of the native mRNA [16]. We have also reported that rabbit globin poly(A)-free mRNA is translated as efficiently as native mRNA during the Enzyme. Nucteosidediphosphate : polynucleotide nucleotidyltransferase (polynucleotide phosphorylase) (EC 2.7.7.8).first 45-min period of incubation in a Krebs-I1 ascites cell-free systems, but upon longer periods of incubation the rate of protein synthesis decreases more rapidly with the poly(A)-free mRNA than with the native mRNA [Ill. To overcome the time limitation of the cell-free system (which is active for only 90 min) we have used Xenopus luevis oocytes, which permit mRNA translation for some days. A pronounced difference between the functional stability of poly(A)-free and native globin mRNA was observed : whereas efficiency of translation of poly(A)-free mRNA in the oocytes is the same as that of the native globin mRNA during the first few hours after injection, 20-48 h later the efficiency of translation drops to about 10% of that of native globin mRNA [12]. Recently we have found that the drop in tem...