scholarly journals Evidence for the presence of a pool of glycerides with a rapid rate of turnover in brown fat from newborn rabbits

1971 ◽  
Vol 123 (4) ◽  
pp. 485-491 ◽  
Author(s):  
B. L. Knight
Keyword(s):  
Half Life ◽  
Specific Radioactivity ◽  
Brown Fat ◽  
Significant Fraction ◽  
Rapid Rate ◽  
Tissue Lipid ◽  
Lipid Store

1. The specific radioactivity of [14C]glycerol released during the incubation of brown fat with [14C]glucose is much greater than that of the tissue lipid glycerol. 2. From a study of the release of [14C]glycerol from pre-labelled brown fat, it is concluded that the tissue contains a pool of glycerides with a higher rate of turnover than those in the main lipid store. 3. This pool contains newly synthesized glycerides, has a half-life of 25–30min and supplies about 25% of the glycerol liberated by brown fat. 4. Thus, a significant fraction of the total14C incorporated from glucose into brown-fat lipids is released as [14C]glycerol during an incubation.

scholarly journals β-Adrenergic stimulation alters oligosaccharide pyrophosphoryl dolichol metabolism in rat parotid acinar cells

1985 ◽  
Vol 231 (2) ◽  
pp. 431-438 ◽  
Author(s):  
S R Grant ◽  
E E Kousvelari ◽  
D K Banerjee ◽  
B J Baum
Keyword(s):  
Half Life ◽  
Specific Radioactivity ◽  
Acinar Cells ◽  
Protein Glycosylation ◽  
Significant Enhancement ◽  
Adrenergic Stimulation ◽  
Parotid Acinar Cells ◽  
Secretory Glycoproteins ◽  
Rat Parotid ◽  
Stimulation Of

beta-Adrenergic stimulation of rat parotid acinar cells markedly increases [3H]mannose incorporation into N-linked glycoproteins [Kousvelari, Grant, Banerjee, Newby & Baum (1984) Biochem. J. 222, 17-24]. More than 90% of this protein-bound [3H]mannose was preferentially incorporated into four secretory glycoproteins. The ratio of [3H]mannose/[14C]leucine present in these individual proteins was 1.7-4-fold greater with isoproterenol-treated cells than with untreated controls. In isoproterenol-stimulated cells, [3H]mannose incorporation into mannosylphosphoryl dolichol and oligosaccharide-PP-dolichol was increased 2-3-fold over that observed in unstimulated cells. Similarly, formation of mannosylated oligosaccharide-PP-dolichol was increased approx. 4-fold in microsomes prepared from isoproterenol-treated cells. Also, turnover of oligosaccharide-PP-dolichol was significantly increased (5-fold) by β-adrenergic stimulation; the half-life for oligosaccharide-PP-dolichol decreased from 6 min in control cells to 1.2 min in isoproterenol-stimulated cells. By 15 min after isoproterenol addition to acinar cells, the specific radioactivity of parotid oligosaccharide moieties increased about 3-fold over the value observed in the absence of the agonist. Taken together, these results strongly suggest that elevation of N-linked protein glycosylation in rat parotid acinar cells after β-adrenoreceptor stimulation resulted from significant enhancement in the synthesis of mannosylphosphoryl dolichol and oligosaccharide-PP-dolichol and the turnover of oligosaccharide-PP-dolichol.

Biliary excretion of dihydro-11-keto-progesterone-4-C14 by isolated perfused liver

1964 ◽  
Vol 207 (5) ◽  
pp. 1030-1034 ◽  
Author(s):  
G. F. Leong ◽  
D. M. Cazes ◽  
M. L. Berliner ◽  
D. L. Berliner
Keyword(s):  
Rat Liver ◽  
Biliary Excretion ◽  
Half Life ◽  
Water Soluble ◽  
Isolated Perfused Rat Liver ◽  
Perfused Liver ◽  
Rapid Rate ◽  
Perfused Rat Liver ◽  
Bile Formation ◽  
Entire Study

The rates of biliary excretion of dihydro-11-keto-progesterone-4-C14 and of its metabolites were studied in the isolated perfused rat liver. The half-life of this steroid in the perfusing blood was 2.5 min, and at 40 min about 75% of the injected steroid had been excreted in bile. Formation of water-soluble steroids (WS St) took place at a rapid rate and by 60 min 100% of the steroids in blood were found to be water soluble. During the entire study the steroids excreted in bile were water soluble and accounted for 97.2–100% (avg. 98.2%). No dihydro-11-keto-progesterone was found to be excreted in the bile. The rate of disappearance from the blood, excretion in the bile, and degree of formation of WS St of this compound when compared with corticosterone and cortisol shows the following pattern: dihydro-11-keto-progesterone > corticosterone > cortisol.

scholarly journals UDP-sugar metabolism in Swarm rat chondrosarcoma chondrocytes

1993 ◽  
Vol 290 (2) ◽  
pp. 563-570 ◽  
Author(s):  
C Sweeney ◽  
D Mackintosh ◽  
R M Mason
Keyword(s):  
Anion Exchange ◽  
Cell Cultures ◽  
Half Life ◽  
Bovine Serum ◽  
Adenine Nucleotides ◽  
Specific Radioactivity ◽  
Sugar Metabolism ◽  
Amino Sugar ◽  
Foetal Bovine Serum ◽  
Pool Sizes

UDP-sugars and adenine nucleotides were extracted from freshly isolated chondrocytes and primary cell cultures and analysed by anion-exchange h.p.l.c. The pool sizes of UDP-N-acetylglucosamine, UDP-N-acetylgalactosamine, UDP-glucose-galactose, UDP-glucuronate and UDP-xylose were 2.9, 1.2, 2.5, 0.6 and 0.03 nmol/10(6) freshly isolated chondrocytes. When chondrocytes were maintained in Dulbecco's modified Eagle medium supplemented with 15% foetal-bovine serum, synthesis of [35S]proteoglycan and [3H]protein decreased over the first 48 h in culture, as did the pools of UDP-glucuronate and ATP. In contrast, the size of the UDP-N-acetylhexosamine pools underwent little change during culture. [35S]Proteoglycan and [3H]protein syntheses were stimulated in cultures supplemented with serum or insulin compared with those maintained in medium alone, in agreement with previous results. However, the UDP-sugar pool sizes were the same in both supplemented and non-supplemented cultures. In cultures maintained in the presence of [1-3H]glucose, the UDP-sugars were labelled to a constant 3H specific radioactivity which was very similar to that of the labelling medium. UDP-N-acetylhexosamines were labelled to constant 3H specific radioactivity with [6-3H]glucosamine as a precursor, but only about 1 in 375 of these UDP-sugars was derived from the amino sugar in the presence of glucose. The half-life (t1/2) for UDP-hexoses, UDP-glucuronate and UDP-N-acetylhexosamines was about 12, 12 and 50 min respectively.

scholarly journals Accumulation and turnover of the classical Folch-Lees proteolipid proteins in developing and adult rat brain

1976 ◽  
Vol 154 (2) ◽  
pp. 265-269 ◽  
Author(s):  
H C Agrawal ◽  
K Fujimoto ◽  
R M Burton
Keyword(s):  
Rat Brain ◽  
Half Life ◽  
Specific Radioactivity ◽  
Proteolipid Protein ◽  
Total Radioactivity ◽  
Myelin Proteins ◽  
Subcutaneous Injections ◽  
Adult Rat ◽  
Adult Rat Brain ◽  
Proteolipid Proteins

The turnover of classical Folch-Lees proteolipid proteins was studied after administration of [2,3-3H]tryptophan to both developing and adult rat brain. The animals were killed from 2h to 250 days after subcutaneous injections of [3H]tryptophan. The measured specific radioactivity in developing brain attained maximum value 24h after the administration of label, whereas the total radioactivity per brain reached a maximum 21 days after injection. The half-life of proteolipid protein from the measured specific radioactivity was 7-20 days, depending on the time-points used for the calculation, whereas calculation from total radioactivity between 28-77 and 91-257 days gave half-lives of 35-40 and 188 days respectively. In contrast, in animals injected at 40 days of age, the half-life from the whole-brain-radioactivity data was 188 days. The problem of the recycling of radioactivity for the synthesis of myelin proteins from either a general or a discrete amino acid pool is discussed.

Effects upon glucose metabolism of feeding a low-or high-roughage diet at two levels of intake to sheep

1975 ◽  
Vol 33 (1) ◽  
pp. 33-44 ◽  
Author(s):  
Essi Evans ◽  
J. G. Buchanan-Smith
Keyword(s):  
Glucose Metabolism ◽  
Half Life ◽  
Venous Blood ◽  
Specific Radioactivity ◽  
Dietary Treatment ◽  
Pool Size ◽  
Entry Rate ◽  
Soya Bean Meal ◽  
Subsequent Withdrawal ◽  
Dietary Treatments

1. To determine the effect of diet and level of energy intake on glucose metabolism in sheep, four dietary treatments consisting of feeding a low-roughage (LR) and a high-roughage (HR) diet at each of two intake levels estimated to provide 586 and 1172 kJ (140 and 280 kcal) digestible energy (DE)/kg body-weight0·75 per d were given to each of eight yearling rams in four different time periods each of 4 weeks duration. Both diets contained 140 g crude protein/ kg using ground maize, mixed hay and soya-bean meal and were given in two meals/d. Estimated DE values of food were verified during the study and actual intakes of DE were within 9·5% of the estimated values.2. To study glucose metabolism, a single intravenous injection of [2-3H]glucose and subsequent withdrawal of nine venous blood samples within 3 h were made in each experiment. Two experiments were conducted on consecutive days for each sheep on each dietary treatment.3. Coefficients of determination (r2) for linear regressions to measure the effect of time after a single injection of [2-3H]glucose on log specific radioactivity of plasma glucose were calculated for fifty-eight experiments. In fifty-six of the experiments, r2 values exceeding 0·95 were obtained.4. Compared to the HR diet, the LR diet increased (P < 0·05) the pool size and decreased (P < 0·05) the half-life of glucose. At both intake levels, the LR diet increased (P < 0·05) the plasma concentration and the entry rate of glucose compared to the HR diet but interaction (P < 0·05) between diet and intake level was attributed to a greater difference obtained between diets at the higher compared to the lower level of food intake. Increasing the level of intake caused a greater (P < 0·05) pool size and space, and a shorter (P < 0·05) half-life of glucose.5. It was concluded that substitution of roughage by concentrate in a ruminant's diet may increase the rate of glucose entry during a short time period after eating.

scholarly journals Radiocarbon in Seawater Intruding into the Israeli Mediterranean Coastal Aquifer

Radiocarbon ◽  
2001 ◽  
Vol 43 (2B) ◽  
pp. 773-781 ◽  
Author(s):  
Y Yechieli ◽  
O Sivan ◽  
B Lazar ◽  
A Vengosh ◽  
D Ronen ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Seawater Intrusion ◽  
Negative Correlation ◽  
Coastal Aquifer ◽  
Carbon Pool ◽  
Significant Fraction ◽  
Rapid Rate ◽  
Tritium Content ◽  
Saline Groundwater ◽  
Dissolved Carbon

Saline groundwaters from the Israeli coastal aquifer were analyzed for their radiocarbon and tritium content to assess the rate of seawater penetration. The low 14C values (28–88 pMC versus 100–117 pMC in seawater) imply an apparent non-recent seawater source, or water-rock interactions along the penetration route. The latter process is supported by measurable tritium values at some locations, which imply a relatively rapid rate of seawater intrusion. In other locations, low tritium values (<2 T.U.) indicate that recent seawater (<50 yr) did not penetrate inland. The low δ13C values in saline groundwater (average of −5.3‰ versus 0‰ in seawater) indicate that the dissolved carbon pool is comprised of a significant fraction of organic carbon. A linear negative correlation between δ13C and 14C implies that this organic source is old (low 14C values).

Determination of mRNA Half-Life in HeLa Cultures by a Poly(A)-Independent Direct Analysis of Specific Radioactivity of mRNA

1975 ◽  
Vol 50 (3) ◽  
pp. 557-562 ◽  
Author(s):  
Ulrich WIEGERS ◽  
Gisela KRAMER ◽  
Karin KLAPPROTH ◽  
Wolfgang REHPENNING ◽  
Helmuth HILZ
Keyword(s):  
Half Life ◽  
Specific Radioactivity ◽  
Direct Analysis ◽  
Mrna Half Life

scholarly journals Biochemical study of cardiac valvular tissue. Biosynthesis in vitro of hexosamine-containing substances in bovine heart valve

1971 ◽  
Vol 124 (1) ◽  
pp. 207-214 ◽  
Author(s):  
Y. Kanke ◽  
Y. Mori ◽  
R. I. Bashey ◽  
A. A. Angrist
Keyword(s):  
Sialic Acid ◽  
Chemical Analysis ◽  
Biochemical Study ◽  
Specific Radioactivity ◽  
Total Radioactivity ◽  
Chemical Components ◽  
Rapid Rate ◽  
Turnover Rates ◽  
Elution Pattern

1. Two distinct hexosamine-containing substances have been obtained from bovine cardiac valvular tissue which was incubated with labelled glucosamine. These were identified as mucopolysaccharides and glycopeptides respectively, both by the elution pattern from a Sephadex G-50 column and by chemical analysis. 2. In the mucopolysaccharide fraction about 80% of both the total hexosamine and total radioactivity were present; the galactosamine/glucosamine ratio of the amounts was about 1.36. 3. The glycopeptide fractions had about 20% of both total hexosamine and total radioactivity; the galactosamine/glucosamine ratio of amounts was about 0.44. In this fraction, over 15% of radioactivity was present in sialic acid. 4. In contrast with the concentrations of the several chemical components, there were remarkable differences in the biosynthetic activities among the four valves; the tricuspid valve had highest specific radioactivity in all components of both substances, followed then in turn by mitral, aortic and pulmonary valves. 5. Glucosamine in mucopolysaccharides had a rapid rate of turnover, followed then in turn by turnover rates of both glucosamine and galactosamine in glycopeptides, and of galactosamine in mucopolysaccharides. The possible significance of these findings is discussed.

scholarly journals Half-life and rate of synthesis of globin messenger ribonucleic acid. Determination of half-life of messenger ribonucleic acid and its relative synthetic rate in erythroid cells

1974 ◽  
Vol 138 (3) ◽  
pp. 487-498 ◽  
Author(s):  
John A. Hunt
Keyword(s):  
Cell Division ◽  
Ribonucleic Acid ◽  
Half Life ◽  
Specific Radioactivity ◽  
Erythroid Cells ◽  
Mrna Synthesis ◽  
Messenger Ribonucleic Acid ◽  
Mrna Half Life ◽  
Division Model ◽  
Basophilic Erythroblast

The specific radioactivity of mouse globin mRNA in blood reticulocytes was measured after injection of [3H]uridine into anaemic mice up to 60h before collection of reticulocytes. From these data, the decay of the acid-soluble nucleotide pool in the marrow and the relative marrow-cell composition it is possible to build models that allow the cell life-times and half-life of mRNA in the erythroid cells of the marrow to be calculated. Best fit of models to these data favour a model with either one or two cell divisions from the onset of mRNA synthesis. The single-cell-division model has cell times of 20, 13 and 7h respectively for the basophilic erythroblast, polychromatophilic erythroblast and reticulocyte. The two-cell-division model has cell times of 12, 12, 12 and 7h for the basophilic erythroblast 1 and 2, polychromatophilic erythroblast and reticulocyte respectively. Both models have an mRNA half-life of 17h and a constant rate of mRNA synthesis until enucleation at the reticulocyte stage, when synthesis stops. A declining rate of mRNA synthesis can be accommodated in a two-cell-division model, when synthesis halves at each cell division and cell times are essentially the same as above, but mRNA half-life is either 9h in the basophilic and polychromatophilic erythroblasts and 17h in the later cells, or 10h in the basophilic erythroblasts and polychromatophilic erythroblasts and 14.5h in later cells. In all cases it is clear that mRNA synthesis occurs over a time-period of only 30–36h and that mRNA cannot be pre-synthesized in precursor erythroid cells.

scholarly journals Dynamics of protozoa in the rumen of sheep

1982 ◽  
Vol 48 (2) ◽  
pp. 399-415 ◽  
Author(s):  
R. A. Leng
Keyword(s):  
Protein Synthesis ◽  
Sodium Chloride ◽  
Half Life ◽  
Rumen Fluid ◽  
Specific Radioactivity ◽  
Microbial Protein ◽  
Replacement Rate ◽  
Irreversible Loss ◽  
Fluid Medium

1. Protozoa were labelled by incubating 100 ml rumen fluid with [14C]choline for 1 h. The protozoa were concentrated by centrifugation and then washed with rumen fluid. This reduced residual14C in the fluid medium to insignificant amounts whilestill retaining the viability of the labelled protozoa. Washing procedures using formal saline (40 g formaldehyde/1 saline (9 g sodium chloride/1)) and saline were developed to isolate protozoa for estimation of specific radioactivity.2. The protozoal pool in freshly-collected rumen fluid incubated in vitro retained 90%of the radioactivity for up to 6 h following addition of14C-I a belled protozoa produced as indicated previously. The specific radioactivity of protozoa did not change during the incubation period.3. Protozoa labelled with [14C]choline and then stored until they died rapidly lost14C to methane when they were incubated in rumen fluid or were injected into the rumen. Some [14C]choline was salvaged under these conditions by the live protozoa present as they apparently incorporated up to 13% of the label from the dead protozoa. However, protozoal debris from the injected solution could also have been present in the isolated protozoa.4. The in vitro results suggested that the protozoal preparations were viable, and that the incorporated choline did not have a turnover in excess of the turnover of nitrogen (i.e. specific radioactivity remained constant with time in vitro) suggesting that the dilution of specific radioactivity of protozoa following mixing of a14C-labelled dose of protozoa represented the rate of irreversible loss and also replacement of protozoa in the rumen.5.14C-labelled protozoa had a half-life in the rumen which was greater than that of rumen fluid and in six animals the protozoal replacement rate was l-4·l mg N/min.6. Losses of14C from labelled protozoa in the rumen in methane or via abomasal digesta were 65 and 35% respectively.7. The results suggest that protozoal growth may be as high as 32% of the total microbial protein synthesis in the rumen but that 65% of the protozoa die and are degraded in the rumen.

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