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41.
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. 相似文献
42.
43.
Human vascular endothelial cells synthesize and release 24- and 26-carbon polyunsaturated fatty acids 总被引:4,自引:0,他引:4
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. 相似文献
44.
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. 相似文献
45.
46.
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. PGF2α was inactive up to a dose of 10 ng. 相似文献
47.
48.
D. H. Krüger L. S. Chernin Sigrid Hansen H. A. Rosenthal D. M. Goldfarb 《Molecular & general genetics : MGG》1978,159(1):107-110
Summary Foreign Flac plasmid DNA which is introduced into potentially restricting E. coli recipient cells can be protected from restriction by preinfecting the recipient cells with UV-inactivated T3 or T7 bacteriophages which express the ocr gene function. The recipient cells survive and are able to replicate themselves as well as the newly acquired plasmid. 相似文献
49.
L-Canavanine is incorporated into the lysozyme synthesized, in response to administration of bacterial cell wall materials, by canavanine-treated larvae of the tobacco hornworm Manduca sexta (Sphingidae). Maximum canavanine incorporation into M. sexta lysozyme occurs when the larvae are provided 1 mg of canavanine g-1 fresh body weight. Analysis of canavanine-containing lysozyme purified from these insects reveals that 21% of the arginine residues are replaced by canavanine; this residue substitution results in a loss of 49.5% of the catalytic activity. When the larvae are provided 0.5 mg of canavanine g-1, 16.5% of the arginine residues are substituted by canavanine and 39.5% of the catalytic activity is lost. Canavanine is also incorporated into the lysozyme induced by canavanine-treated pupae of the giant silk moth Hyalophora cecropia (Saturnidae). In contrast, replacement of 17% of the arginine in H. cecropia lysozyme by canavanine fails to affect the catalytic activity. We have determined the primary structure of M. sexta lysozyme and compared it with the primary structure of H. cecropia lysozyme which has been described elsewhere. M. sexta lysozyme has an arginine at positions 23, 42, and 107. H. cecropia contains serine, lysine, and lysine, respectively, at these locations. The ability of incorporated canavanine to inhibit M. sexta lysozyme activity selectively may result from the fact that replacement of any one of the 3 arginine residues at position 23, 42, or 107 by canavanine causes the loss of catalytic activity. 相似文献
50.
Miguel A. Pérez-Pinzón Myron Rosenthal Peter L. Lutz Thomas J. Sick 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(1):68-73
Intact turtle brain provides a useful model for the study of anoxia and potential survival strategies, since this tissue maintains transmembrane ion gradients and ATP levels during prolonged anoxia and recovers functional activity afterwards. Since isolated tissues offer experimental advantages, the present study sought to determine effects of anoxia on the isolated turtle cerebellum and to define relationships between anoxia survival and glucose supply. In normoxia, the extracellular potassium ([K+]o) activity and evoked potentials were maintained with 5 mM glucose, but 20 mM glucose was required to maintain adenosine triphosphate (ATP) levels and prevent significant increases in [K+]o during anoxia. Inhibition of glycolysis by iodoacetic acid (IAA) during anoxia provoked large increases in [K+]o at all glucose levels. These results demonstrate the usefulness of the isolated turtle cerebellum for studies of anoxic survival since this tissue can maintain ATP levels and [K+]o during prolonged anoxia with 20 mM glucose in the artificial cerebrospinal fluid medium. They also suggest the presence of a Pasteur effect at least during the transition to a hypometabolic state. 相似文献