Activation of a muscle-specific enhancer by the Ski proto-oncogene.

In transgenic mice, muscle-specific expression of the c-ski oncogene induces hypertrophy exclusively in a subset of fast muscle fibers. Here we report that regulatory elements from two genes expressed in fast fibers, myosin light chain 1/3 (MLC) and muscle creatine kinase (MCK), were activated when co-transfected with c-ski expression vectors in myoblasts. The expression from the MLC enhancer was reduced when the c-ski oncogene was cotransfected with MyoD into NIH3T3 fibroblasts. Activation of the MLC enhancer by Ski also occurred in vivo, since bigenic progeny generated by mating MLC-CAT and MSV-skitransgenic mice displayed higher CAT activity in their muscles than did the MLC-CAT parental line. Identification of gene targets for the fiber-specific action of the c-ski gene product provides a molecular model that could be used for the further dissection of Ski-induced hypertrophy, both in tissue culture and in vivo.     

Human vascular endothelial cells synthesize and release 24- and 26-carbon polyunsaturated fatty acids

Various mutants were isolated from a microvirid (isometric single-stranded DNA) phage alpha 3, by mutagenesis with hydroxylamine or nitrous acid. They were divided into eight complementation groups, and mainly by genetic crosses the gene alignment was determined as -A-B-C'-D-J'-F-G-H-. Except for groups C' and J', each defective gene product was clearly discerned in electropherograms of proteins extracted from the phage-infected suppressor-negative (Su-) Escherichia coli. Only gene A mutants abolished synthesis of the progeny replicative-form DNA (RF), whereas mutants belonging to groups B, C', D, E, F and J' affected RF replication at late stage, as well as synthesis of the single-stranded DNA (SS). Additional properties of several mutants are also discussed.     

Radiochemical synthesis of DL-canaline and the colorimetric assay of canaline

A procedure is available for the production of DL-[carboxy-14C]canaline from [14C]cyanide by reaction of ethyl N-hydroxyacetimidate and acrolein to form ethyl N-[3-oxopropoxy]acetimidate. The reaction product is converted to the nitrile and then to the hydantoin derivative of DL-canaline; alkaline hydrolysis produces the free amino acid (2-amino-4-aminooxypropionic acid). This procedure can be extended to the production of DL-[carboxy-14C]canavanine by guanidination of C-1-labeled DL-canaline with O-methylisourea. A markedly improved colorimetric assay for canaline has been achieved by a procedure involving carbamylation of canaline with cyanate to form O-ureidohomoserine (2-amino-4-ureidooxybutyric acid). Colorimetric analysis of the latter amino acid markedly enhances the sensitivity, reproducibility, and accuracy of the analysis of L-canaline from biological materials.     

I-A Mutation resulted in a selective loss of an antigen-specific Ir gene function

The immune responses to several antigens were compared in the I-A mutant mouse strain B6.C-H-2^bm12 and the wild-type strain C57BL/6. With a lymph node cell proliferation assay, the response to two of these antigens, beef insulin and (TG)A-L, was demonstrated to be controlled by a gene in the I-A^b region. B6.C-H-2^bm12 mice failed to respond to beef insulin, while their responses to (TG)A-L, DNP-OVA and PPD were comparable with those of the wild-type strain C57BL/6. Taken together with previous studies, these data suggest that the product of a single pleiotropic I-A gene, an la molecule, functions as a histocompatibility, la, and MLR antigen, as well as a necessary component for Ir gene function. Furthermore, the data reported here demonstrate that la molecules have multiple functional “Ir determinants,” one of which has been altered in the B6.C-H-2^bm12 mutant. The B6.C-H-2^bm12 mice, therefore, represent a powerful analytical tool for the understanding of the cellular and molecular basis for Ir gene control of the immune response.     

Opposition of the vasopressin-induced vasoconstriction in the isolated perfused rat kidney by some prostaglandins

PGE₂ can vasoconstrict or vasolidate the isolated Krebs-perfused rat kidney depending on the tone of the renal vasculature. Thus, it is weakly constrictor (threshold 5–10 ng bolus dose) in the perfused kidney whose perfusion pressure is 47 ± 2 SD mmHg (n = 6), but becomes a vasodilator (threshold ～ 10 pg) in the kidney whose perfusion pressure has been raised to 73 ± 6 SD mmHg (n = 6) or 121 ± 8 SD mmHg (n = 6) through constant infusion of Vasopressin (0.1 and 0.25 mU/ml respectively). PGE₁ was equally effective as PGE₂ while other PGs, I₂, I₁, and 6-keto E₁, were less effective in opposing vasoconstriction. PGF_2α was inactive up to a dose of 10 ng.     

Fibrinolytic activity associated with cultured human neoplastic and normal cells

Summary Fibrinolytic activity was studied in a number of different established as well as secondary human cell cultures derived from both malignant and normal tissues. The ability to degrade [¹²⁵I]-labeled fibrin was found to be characteristic of some malignant cultures as well as some normal cultures, and to be dependent upon the presence of serum. For the most part, this activity was detected in cultures with a relatively shortin vitro passage history (<30 passages). Low passaged colon and rectal carcinoma cells, HCT-8 and HRT-18, as well as normal rectal, colon and foreskin fibroblasts were positive for fibrinolytic activity, while long established (>100 passages) cultures of malignant cells (colon carcinoma, HeLa, Hep-2, KB) as well as normal cells (HEI, AV₃) were negative. It is proposed that although some normal cells synthesize plasminogen activators, the fibrinolytic capability of both malignant and normal cells may be lost on prolongedin vitro cultivation.