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- Synthesis and degradation of acetylcholine receptors in rat skeletal muscles were measured in organ culture. The rate of de novo biosynthesis and incorporation of acetylcholine receptors into extrajunctional membranes of denervated muscles was measured by determining the rate of appearance of [1] [2H, 13C, 15N]-acetylcholine receptors when muscles were cultured in medium containing [1] [2H, 13C, 15N]-amino acids. Denervated extensor digitorum longus and soleus muscles were found to synthesize new receptors for several days in organ culture at an average rate of 1.4%/h. The degradation rates for extrajunctional and junctional acetylcholine receptors were estimated by irreversibly labeling acétylcholine receptors on muscles with radioactive iodinated α-bungarotoxin and measuring the rate of release into the culture medium of mono- and di-iodotyrosine, breakdown products of the radioactive α-bungarotoxin. The rates of this proteolytic process yielded average lifetimes of 22 h and 13 days for [125I]α-bungarotoxin bound to extrajunctional and junctional receptors, respectively, probably reflecting the average lifetimes of the acetylcholine receptors. Electrical stimulation at 100Hz for 1 s every 80s, producing visible contraction, but not maximal tetanic tension, barely altered the rate of incorporation of new acetylcholine receptors into the extrajunctional plasma membrane of extensor digitorum longus and soleus muscles, even when the stimulation continued for 5 days. Supra-maximal stimulation, resulting in maximal tetanic tension, with the same stimulation pattern produced a rapid decline of 10–20% in the rate of new receptor production and a corresponding decline in overall protein synthesis. Stimulation beyond 18–24 h (up to 68 h) resulted in a further decrease in new receptor production to about 30% of the control rate, but not more. Stimulation for longer than 16 h produced less than a 5–10% decrease in overall protein synthesis, compared with control muscles. The same pattern of electrical stimulation, producing maximal tetanic tension, had no effect on the apparent degradation rate of extrajunctional receptors in denervated muscles. Our results show that denervated adult muscle can be maintained in organ culture for at least 1 week, and that the muscles in culture will continue to degrade acetylcholine receptors and to synthesize new receptors, even when electrically stimulated for 5 days. The significance of this study is that electrical stimulation, producing frequent tetanic contractions, can affect extrajunctional acetylcholine receptor metabolism by selectively decreasing de novo synthesis, the receptor degradation remaining unchanged. The precise control point in the biosynthetic process has yet to be determined. However, our results indicate that electrically induced activity does exert a regulating influence, relatively rapidly, on extrajunctional acetylcholine receptor metabolism on muscles maintained in vitro. (1)
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Mechanism Of Decarboxylation Of Glycine And Glycolate By Isolated Soybean Cells, David J. Oliver
Mechanism Of Decarboxylation Of Glycine And Glycolate By Isolated Soybean Cells, David J. Oliver
David J. Oliver
Isolated soybean leaf mesophyll cells decarboxylated exogenously added [1-14C]glycolate and [1-14C]glycine in the dark. The rate of CO2 release from glycine was inhibited over 90% by isonicotinic acid hydrazide and about 80% by KCN, two inhibitors of the glycine to serine plus CO2 reaction. The release of CO2 from glycolate was inhibited by less than 50% under the same conditions. This indicates that about 50% of the CO2 released from glycolate occurred at a site other than the glycine to serine reaction. The sensitivity of this alternative site of CO2 release to an inhibitor of glycolate oxidase (methyl-2-hydroxy-3-butynoate) but not …
Vesicular-Arbuscular Mycorrhiza Influence Growth But Not Mineral Concentrations In Seedlings Of Eight Sweetgum Families, Richard C. Schultz, Paul P. Kormanik, W. Craig Bryan, G. H. Brister
Vesicular-Arbuscular Mycorrhiza Influence Growth But Not Mineral Concentrations In Seedlings Of Eight Sweetgum Families, Richard C. Schultz, Paul P. Kormanik, W. Craig Bryan, G. H. Brister
Richard C. Schultz
Seedlings of eight half-sib sweetgum (Liquidambar styraciflua L.) families were grown for 6 months in a fumigated soil mixture, with or without inoculum from a mixture of Glomus mosseae and Glomus etunicatus fungi, at levels of 140, 280, 560, and 1120 kg/ha of 10-10-10 fertilizer. All seedlings received three additions of 187 kg/ha of N during the growing season. Inoculated seedlings had significantly greater biomass, height, and stem diameters at each fertilizer level than nonmycorrhizal control seedlings. Significant differences in growth occurred between families in mycorrhizal plants. However, fertilizer did not significantly affect growth or nutrient uptake of the seedlings. …
Comparison Of Carbon And Nitrogen Content Of Infected And Uninfected Snails, Succinea Ovalis, And The Trematode Leucochloridium Variae, A Burky, Daniel J. Hornbach
Comparison Of Carbon And Nitrogen Content Of Infected And Uninfected Snails, Succinea Ovalis, And The Trematode Leucochloridium Variae, A Burky, Daniel J. Hornbach
Daniel J. Hornbach
No abstract provided.
Brain Mechanisms For Offense, Defense And Submission, David B. Adams
Brain Mechanisms For Offense, Defense And Submission, David B. Adams
David Adams
Biosynthesis And Degradation Of Acetylcholine Receptors In Rat Skeletal Muscles. Effects Of Electrical Stimulation, Diana Linden, D.M. Fambrough
Biosynthesis And Degradation Of Acetylcholine Receptors In Rat Skeletal Muscles. Effects Of Electrical Stimulation, Diana Linden, D.M. Fambrough
Diana Linden
Synthesis and degradation of acetylcholine receptors in rat skeletal muscles were measured in organ culture. The rate of de novo biosynthesis and incorporation of acetylcholine receptors into extrajunctional membranes of denervated muscles was measured by determining the rate of appearance of [1] [2H, 13C, 15N]-acetylcholine receptors when muscles were cultured in medium containing [1] [2H, 13C, 15N]-amino acids. Denervated extensor digitorum longus and soleus muscles were found to synthesize new receptors for several days in organ culture at an average rate of 1.4%/h. The degradation rates for extrajunctional and junctional acetylcholine receptors were estimated by irreversibly labeling acétylcholine receptors on …
Immunobiology Of Malaria, Clarence Lee, Yvonne Hogan, Georgiana Aboko-Cole
Immunobiology Of Malaria, Clarence Lee, Yvonne Hogan, Georgiana Aboko-Cole
Clarence Lee
Removal Of Raw Peanut Flavor And Odor In Peanut Flour Processed By Direct Solvent Extraction1, Lawrence A. Johnson, J. T. Farnsworth, R. J. Garland, E. W. Lusas
Removal Of Raw Peanut Flavor And Odor In Peanut Flour Processed By Direct Solvent Extraction1, Lawrence A. Johnson, J. T. Farnsworth, R. J. Garland, E. W. Lusas
Lawrence A. Johnson
Peanut slices can be directly extracted with hexane yielding more soluble protein and better color than pre-press solvent extraction; however, flavor and odor are characterized as raw and “green beany”. The utilization of secondary extraction with hexane: ethanol azeotrope, hexane: methanol azeotrope and absolute ethanol subsequent to hexane extraction significantly improved flavor and odor characteristics of peanut flour. Hexane: propanol azeotrope did not significantly improve sensory evaluations. Hexane: ethanol azeotrope did not reduce soluble protein, yielding an NSI value of 95%. Hexane: methanol azeotrope and absolute ethanol slightly reduced NSI to 88% and 92% respectively. Color of peanut flour was …
Germination Of Cow Parsnip Seeds From Grizzly Bear Feces, James M. Novak, Roger D. Applegate, Lynn L. Rogers, David A. Casteel
Germination Of Cow Parsnip Seeds From Grizzly Bear Feces, James M. Novak, Roger D. Applegate, Lynn L. Rogers, David A. Casteel
James M. Novak
No abstract provided.
Nest Desertion By The Pinyon Jay, Larry Clark
Hidrometalurjide Yeni, Fathi Habashi
Hidrometalurjide Yeni, Fathi Habashi
Fathi Habashi
Turkish translation of F. Habashi, “Recent Advances in Hydrometallurgy,” Proceedings International Mineral Processing Congress, Warsaw, 1979, edited by J. Laskowski, published by Elsevier, pp. 902–935
Nutritional Ecology Of Microtine Rodents: Digestibility Of Forage, George Batzli, F Cole
Nutritional Ecology Of Microtine Rodents: Digestibility Of Forage, George Batzli, F Cole
F. Russell Cole
No abstract provided.
Rna Sequencing Provides Evidence For Allelism Of Determinants Of The N-, B-, Or Nb- Tropism Of Murine Leukemia Viruses, Jean Rommelaere, Helen Donis-Keller, Nancy Hopkins
Rna Sequencing Provides Evidence For Allelism Of Determinants Of The N-, B-, Or Nb- Tropism Of Murine Leukemia Viruses, Jean Rommelaere, Helen Donis-Keller, Nancy Hopkins
Helen Donis-Keller
Previous genetic and biochemical studies identified three large RNAase T1-resistant oligonucleotides, each associated with either the N-, B- or NB-tropism of murine C-type viruses of BALB/c origin. These oligonucleotides were shown to lie in the 5′ third of the oligonucleotide maps of their respective viruses. We sequenced the three oligonucleotides and found that they share a 10 base sequence. Together these observations provide good evidence that the determinants of N-, B- or NB-tropism monitored by the three oligonucleotides are allelic.The oligonucleotides associated with N- and B-tropism differ in sequence at four of sixteen nucleotides, while the B- and NB-tropism-associated oligonucleotides …