Plasma pool source for fibrinogen synthesis in postabsorptive conscious dogs

1991 ◽  
Vol 260 (4) ◽  
pp. E581-E587
Author(s):  
W. M. Bennet ◽  
M. W. Haymond
Keyword(s):  
Protein Synthesis ◽  
Hepatic Artery ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
The Other ◽  
Plasma Pool ◽  
Arterial Plasma ◽  
Plasma Leucine ◽  
Hepatic Protein Synthesis ◽  
Potential Precursor

To assess the contributions of leucine and alpha-ketoisocaproate (KIC) derived from the portal vein vs. hepatic artery for hepatic protein synthesis, 14-postabsorptive dogs were infused simultaneously with [1-14C]- and [4,5-3H]leucine or [1-14C]- and [4,5-3H]KIC. On one occasion one tracer was infused via a leg vein and the other via mesenteric infusion catheters, and dogs were restudied with both tracers infused systemically. The ratios of systemically to portally infused tracers in portal and arterial plasma leucine were used as indexes of the radioactivity in the potential precursor pools and in fibrinogen-bound leucine as a paradigm of hepatic protein synthesis. In the dogs given leucine tracers, the relative proportions of systemically to portally infused radioactivity in portal free leucine (0.50 +/- 0.06) were lower (P less than 0.001) than in arterial free leucine (1.22 +/- 0.03) and not different from that bound in fibrinogen (0.43 +/- 0.02). In the dogs infused intraportally with KIC, these values were 0.81 +/- 0.04, 0.97 +/- 0.05, and 0.74 +/- 0.05, respectively. In the control studies these ratios were not significantly different from the expected value of 1.0. The results suggest that, in postabsorptive dogs, fibrinogen is exclusively synthesized from portally delivered leucine with little or no contribution from the hepatic artery, whereas portally delivered KIC contributes little directly to fibrinogen synthesis. These data are consistent with zonation of hepatic amino acid metabolism and/or protein synthesis.

scholarly journals Amino acid metabolism and protein synthesis in lactating rats fed on a liquid diet

1990 ◽  
Vol 270 (1) ◽  
pp. 77-82 ◽  
Author(s):  
T Barber ◽  
J García de la Asunción ◽  
I R Puertes ◽  
J R Viña
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
High Protein ◽  
The Other ◽  
Small Intestinal Mucosa ◽  
Urea Synthesis ◽  
Carbamoyl Phosphate ◽  
Liver Size

1. Amino acid metabolism was studied in control virgin rats, lactating rats and virgin rats protein-pair-fed with the lactating rats (high-protein virgin rats). 2. Urinary excretion of nitrogen and urea was higher in lactating than in control virgin rats, and in high-protein virgin rats it was higher than in lactating rats. 3. The activities of urea-cycle enzymes (units/g) were higher in high-protein virgin than in lactating rats, except for arginase. In lactating rats the activities of carbamoyl-phosphate synthase, ornithine carbamoyltransferase and argininosuccinate synthase were lower than in control virgin rats. When the liver size is considered, the activities in lactating rats were similar to those in high-protein virgin rats, except for arginase. 4. N-Acetylglutamate content was higher in high-protein virgin rats than in the other two groups. 5. The rate of urea synthesis from precursors by isolated hepatocytes was higher in high-protein virgin rats than in the other two groups. 6. The flooding-dose method (L-[4-3H]phenylalanine) for measuring protein synthesis was used. The absolute synthesis rates of mammary gland, liver and small-intestinal mucosa were higher in lactating rats than in the other two groups, and in high-protein virgin rats than in control virgin rats 7. These results show that the increased needs for amino acids during lactation are met by hyperphagia and by a nitrogen-sparing mechanism.

Amino Acid Metabolism in Plants. II. Transamination Reactions of Free Protein Amino Acids in Cell-Free Extracts of Cotyledons and Growing Tissues of Bushbean Seedlings (Phaseolus vulgaris L.)

1972 ◽  
Vol 50 (5) ◽  
pp. 538-542 ◽  
Author(s):  
J. C. Forest ◽  
F. Wightman
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
The Other ◽  
Amino Group ◽  
Phaseolus Vulgaris L ◽  
Keto Acids ◽  
Protein Amino Acids

The different transaminase reactions for 22 protein amino acids were investigated in extracts of cotyledons and growing tissues of 8-day-old bushbean seedlings when either α-ketoglutarate, oxaloacetate, pyruvate, or glyoxylate was used as amino group acceptor. The results indicate that both cotyledons and growing tissues exhibited a similar pattern of transaminase activities with respect to the amino acids normally required for protein synthesis. It was found that with the exception of proline, hydroxyproline, and cystine which did not appear to be transaminated, and of serine and threonine which were transaminated only when pyruvate or glyoxylate was provided as the amino group acceptor, all the other 17 amino acids were transaminated to different extents when each of the four keto acids tested was supplied as the amino group acceptor. Glutamic acid, aspartic acid, and alanine were, by far, the best amino group donors and α-ketoglutarate was generally found to be the best amino acceptor. Consideration is given to the number and substrate specificity of the aminotransferases catalyzing the reactions demonstrated in this study.

Isolation and characterisation of guanine auxotrophs in Saccharomyces cerevisiae

1979 ◽  
Vol 25 (3) ◽  
pp. 380-389 ◽  
Author(s):  
W. J. E. Gardner ◽  
R. A. Woods
Keyword(s):  
Amino Acid Metabolism ◽  
Enzyme Assay ◽  
Acid Metabolism ◽  
The Other ◽  
Riboflavin Biosynthesis ◽  
Purine Derivatives ◽  
Mendelian Segregation ◽  
Assay Procedure ◽  
Aromatic Amino Acid Metabolism

Mutants of yeast which are auxotrophic for guanine have been isolated from two prototrophic haploid strains, one of which carried the suppressor of purine excretion, su-pur, and the other carried the alternative allele, su-pur+. The mutants were allocated to three genes, gua1, gua2, and gua3, between which no close linkage was demonstrable. Mutants of all three genes were recessive and showed normal Mendelian segregation in crosses. The gene gua1 was shown by an in vivo enzyme assay procedure to specify guanosine 5′-phosphate (GMP) synthetase, the second enzyme involved in the biosynthesis of GMP from inosine 5′-phosphate (IMP). Mutants of this gene excrete large amounts of purine derivatives, predominantly xanthosine, into guanine-free, but not into guanine-supplemented, medium. The gene gua2 is probably involved in the biosynthesis of riboflavin from guanine nucleotides; the phenotype of these mutants suggests a possible interaction between aromatic amino acid metabolism and riboflavin biosynthesis. No role for gua3 can be assigned on the evidence so far available, but it is not involved in the specification of IMP dehydrogenase, the first enzyme involved in the synthesis of GMP and IMP.

scholarly journals Rates of protein synthesis in skin and bone, and their importance in the assessment of protein degradation in the perfused rat hemicorpus

1981 ◽  
Vol 194 (1) ◽  
pp. 373-376 ◽  
Author(s):  
V R Preedy ◽  
P J Garlick
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Protein Degradation ◽  
Muscle Tissue ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Muscle Protein ◽  
Muscle Metabolism ◽  
Muscle Protein Degradation

The perfused rat hemicorpus preparation, which has frequently been used to study muscle metabolism, contains 39% by weight of non-muscle tissue such as skin and bone. Both the concentration of RNA and the incorporation of [U-14C]tyrosine into protein indicate that the non-muscle components are more active in protein synthesis than is muscle. These observations have important implications for studies of amino acid metabolism, and in particular for the measurement of muscle protein degradation in the hemicorpus.

scholarly journals Reducing plasma HIV RNA improves muscle amino acid metabolism

2005 ◽  
Vol 288 (1) ◽  
pp. E278-E284 ◽  
Author(s):  
Kevin E. Yarasheski ◽  
Samuel R. Smith ◽  
William G. Powderly
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Metabolism ◽  
Acid Metabolism ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Synthesis Rate ◽  
Protein Synthesis Rate ◽  
Hiv Rna ◽  
Muscle Protein Synthesis Rate

We reported (Yarasheski KE, Zachwieja JJ, Gischler J, Crowley J, Horgan MM, and Powderly WG. Am J Physiol Endocrinol Metab 275: E577–E583, 1998) that AIDS muscle wasting was associated with an inappropriately low rate of muscle protein synthesis and an elevated glutamine rate of appearance (Ra Gln). We hypothesized that high plasma HIV RNA caused dysregulation of muscle amino acid metabolism. We determined whether a reduction in HIV RNA (≥1 log) increased muscle protein synthesis rate and reduced Ra Gln and muscle proteasome activity in 10 men and 1 woman (22–57 yr, 60–108 kg, 17–33 kg muscle) with advanced HIV (CD4 = 0–311 cells/μl; HIV RNA = 10–375 × 103 copies/ml). We utilized stable isotope tracer methodologies ([13C]Leu and [15N]Gln) to measure the fractional rate of mixed muscle protein synthesis and plasma Ra Gln in these subjects before and 4 mo after initiating their first or a salvage antiretroviral therapy regimen. After treatment, median CD4 increased (98 vs. 139 cells/μl, P = 0.009) and median HIV RNA was reduced (155,828 vs. 100 copies/ml, P = 0.003). Mixed muscle protein synthesis rate increased (0.062 ± 0.005 vs. 0.078 ± 0.006%/h, P = 0.01), Ra Gln decreased (387 ± 33 vs. 323 ± 15 μmol·kg fat-free mass−1·h−1, P = 0.04), and muscle proteasome chymotrypsin-like catalytic activity was reduced 14% ( P = 0.03). Muscle mass was only modestly increased (1 kg, P = not significant). We estimated that, for each 10,000 copies/ml reduction in HIV RNA, ∼3 g of additional muscle protein are synthesized per day. These findings suggest that reducing HIV RNA increases muscle protein synthesis and reduces muscle proteolysis, but muscle protein synthesis relative to whole body protein synthesis rate is not restored to normal, so muscle mass is not substantially increased.

scholarly journals Proliferation of Megaloblasts in Pernicious Anemia as Observed from Nucleic Acid Metabolism

Blood ◽  
1968 ◽  
Vol 31 (3) ◽  
pp. 292-303 ◽  
Author(s):  
YATARO YOSHIDA ◽  
AKIO TODO ◽  
SHIGERU SHIRAKAWA ◽  
GYOICHI WAKISAKA ◽  
HARUTO UCHINO
Keyword(s):  
Protein Synthesis ◽  
Nucleic Acid ◽  
Pernicious Anemia ◽  
Acid Metabolism ◽  
Cellular Level ◽  
The Other ◽  
Nucleic Acid Metabolism ◽  
Dna Values ◽  
Rna And Protein Synthesis ◽  
S Period

Abstract In order to elucidate the nature of the megaloblastic lesion at the cellular level, DNA, RNA, and protein synthesis was studied in megaloblasts of pernicious anemia. While microphotometric estimation of DNA content showed an increase in cells with DNA values ranging around the 4c value, autoradiographic studies with H3-thymidine indicated, rather, a decreased ability to synthesize DNA. Combined microphotometric and autoradiographic studies suggested the impaired DNA synthesis with occasional arrests of synthesis, as well as the prolongation of the S period with or without the prolongation of the G2 period. On the other hand, active incorporation of H3-uridine and H3-leucine indicated active or unaffected RNA and protein synthesis. Vitamin B12 treatment rapidly corrected these aberrant patterns of synthesis. The significance of these findings has been discussed in relation to the mechanism of megaloblastic hemopoiesis.

Sign in / Sign up

Export Citation Format

Share Document