Apparent Uptake Research Articles

Uptake and Growth-promoting Activity of Indoleacetic Acid in Segments of Cold-hardened Wheat Coleoptiles

Seedings of winter wheat (Triticum aestivum L. cv. Kharkov MC 22) were grown at 24 C (unhardened) and 4 C (hardened). Indoleacetic acid (IAA) was added to excised coleoptile segments after lengthy incubation and their responses were determined by photometric auxanometry at both 25 C and 5 C. The segments' rates of uptake of (14)CIAA were also compared at both temperatures. Cold hardening had no significant effect on the rates of elongation and uptake in a saturating concentration of IAA (2 to 10 muM) at either temperature. Elongation was more sensitive to temperature of measurement than was uptake. At suboptimal concentrations of IAA and 25 C, hardened coleoptiles took up [2-(14)C]-IAA twice as fast but elongated half as fast as unhardened coleoptiles. This and the lack of effect of cold hardening on apparent uptake of [1-(14)C]-IAA raised the possibility that a higher rate of IAA-decarboxylation was coupled with the higher rate of uptake of IAA by hardened coleoptiles. Homeostatic hormonal regulation was also evident in the same endogenous rates of elongation of segments of cold-hardened and unhardened coleoptiles.

Apparent uptake of purines by the human heart.

Apparent uptake of purines by the human heart.

Relation of cell growth and colicin tolerance to vitamin B12 uptake in Escherichia coli

The uptake of vitamin B12 was measured in cells of Escherichia coli whose growth had been inhibited by any of a variety of treatments. In all cases, the secondary, energy-dependent phase of B12 uptake was depressed in proportion to the decrease in growth rate, but uptake was constant in cells growing logarithmically at different rates. The depression of B12 uptake activity was independent of the site of cell metabolism affected by the inhibitor or by its effect on cell viability, and was both more rapid and of greater degree than the effects on the uptake of any of the six amino acids tested. The decline was not affected by inhibitors of either cell division or proteolysis and was manifested without any apparent decrease in the surface B12 binding activity. Transport activity was rapidly regained upon reversal of the inhibition of protein synthesis. Prompted by this response, the uptake of B12 was contrasted to the apparent uptake of the E colicins, which share the same outer membrane receptor. Sensitivity to colicin E1, measured by its inhibition of proline uptake, was not affected by growth inhibition by antibiotic treatment. Finally, there was no specific depression of B12 uptake in cells rendered colicin tolerant either by mutation or as a consequence of phage f1 infection.

Auxin inhibition of acid-and fusicoccin-induced elongation in lentil roots

Both acid pH (4.0) and fusicoccin (FC) strongly stimulate root elongation in intact lentil (Lens culinaris Med.) seedlings. FC-induced elongation is apparently mediated by FC-enhanced H(+) secretion since the toxin induces massive secretion of H(+) in these roots after a latent period of less than 5 min. Auxin (indole-3-acetic acid) strongly inhibits elongation in control roots as well as acid-induced and FC-induced root elongation. Treatment of apical root segments with auxin causes only a slight apparent uptake of H(+) and has no inhibitory effect on FC-induced H(+) secretion, whether the hormone is given before or after the toxin. Auxin induces ethylene production in excised roots of lentil but the latent period is at least 30 min while inhibition of root elongation by IAA is maximal within 30 min. It is concluded that the inhibitory action of auxin on acid-and fusicoccin-induced root elongation is a direct effect, independent of auxin-induced ethylene production or auxin-mediated modification of cell-wall pH.

Reversible independent alterations in glucose transport and metabolism in cultured human cells deprived of glucose.

We have measured uptake of 3H-hexoses into diploid human cells by exposing them to brief pulses of isotopic sugar during the log-growth, subconfluent-growth, and confluent-growth (contact inhibited) phases of the strain HSWP derived from human skin. 3H-deoxyglucose appears to be taken up three times faster than 3H-glucose. After exposure to 3H-glucose for longer than one minute, the cells excrete approximately 70% of the isotope into the medium as lactate. If lactate production (and hence excretion) is abolished by treating the cellls with iodoacetic acid or dinitrofluorobenzene, neither of which inhibits transport, the uptake of 3H-glucose is found to be in fact somewhat larger than that of 3H-deoxyglucose. If cells are deprived of glucose for 24 hours, apparent uptake of 3H-glucose is enhanced 10-fold or more. This latter increase is accounted for by 2- to 3-fold enhancement of true transport plus retention of greater than 90% of the radioactivity, since little lactate is formed or excreted in glucose-deprived cells. Deoxyglucose, galactose, or pyruvate when present during glucose deprivation each have quantitatively different effects on the cells' capacity to produce lactate from a short pulse of glucose, but none of them prevents the enhancement of hexose transport. After restoration of 5 mM glucose to starved cells, their metabolsim returns to normal (in the sense that approximately 70% of the glucose taken up in a pulse is again excreted as lactate), with a half-time of 0.5 hour; but the transport of hexoses returns to control levels much more slowly, with a half-time of approximately 6 hours. The two processes appear to be independently regulated.

Chromium uptake and transport in barley seedlings (Hordeum vulgare L.)

Potassium chromate is more toxic to the growth of barley in solution culture than chromic chloride, though apparent uptake of the latter is much faster. Inhibitor studies indicate that CrO4 (2-) uptake is "active" whereas Cr(3+) uptake is passive, demonstrating that the two forms do not share a common uptake mechanism. Studies on the form of Cr inside root cells show that in plants fed CrO4 (2-) the Cr remains largely unchanged whereas in plants fed Cr(3+) a little CrO4 (2-) (0.5 per cent) is produced. This conversion is dependent on the presence of living material and is probably enzymatic. Chromate uptake follows Michaelis-Menten kinetics at low concentration and is competitively inhibited by sulphate. Transport of chromium up the root is very slow, accounting for the low levels of Cr in the shoots. Chromate is transported better than Cr(3+) though still to a very limited extent. These experiments provide a physiological basis for previous observations.

Some observations on the fluorometric determination of glucose in freshwater

The sensitivity of the fluorometric determination of glucose is occasionally severely reduced by quenching in profundal samples. The reproducibility of the method in such samples was investigated, as were the effects of dilution of mud samples and substrate concentration on the apparent glucose uptake rate. Observations on the disappearance of glucose from solution in the presence of mud showed that dilution of the mud could produce serious overestimates of the uptake rate. Analysis of the kinetics of uptake in undisturbed mud cores suggests that rough estimates of the kinetic parameters may be obtained for samples where the addition of radioactive tracers is undesirable.

The effects of hyperlipidemia on lbpoprotein metabolism in squirrel monkeys and rabbits

We studied the metabolism of different classes of lipoprotein in squirrel monkeys and rabbits. Lipoproteins were labeled in vivo in donor animals with [ 3H]leucine and [ 3H] cholesterol. The rate of disappearance from plasma of recipient squirrel monkeys of the protein moiety of the very low density lipoproteins was rapid, that of high density lipoproteins slow, and the rate for low density lipoproteins was intermediate. The fractional turnover of the apoprotein of low density lipoproteins was slightly reduced in hyperlipidemic monkeys, but the absolute rates of synthesis and catabolism were increased. Hyperlipidemia in rabbits resulted in a dramatic reduction in the fractional catabolic rate of low density lipoprotein apoprotein. Hyperlipidemia in the donors of biosynthetic low density lipoproteins also influenced the rates of catabolism in rabbits. We showed with cycloheximide that although there was recycling of [ 3H]leucine into other proteins, the reutilization of leucine from low density lipoproteins for nascent low density lipoproteins was not significant. In most tissues the ratio of cholesterol:protein radioactivity was much greater than that for plasma 24 h after administration of labeled low density lipoproteins, but the ratios for aortic intima plus inner media and for plasma low density lipoproteins were similar. The presence of atherosclerosis resulted in a large increase in the apparent uptake of low density lipoproteins by the aortas of rabbits and monkeys.

Primary Tissue Culture of Normal Adult Human Decapsulated Adrenal Cortex: Radioautographic Studies on the Metabolic Effects of ACTH<sub>1-2</sub><sub>4</sub>

ACTH-deprived primary normal adult human adrenocortical cells on the 23rd day in vitro were found to lack any DNA synthetic and proliferative activity, but incorporated uridine-3H and 1-leucine-3H actively. In cortical cells of the same age treated for 2 and 7 days with ACTH1-24 (3 X 10(-6) M) the incorporation of the precursors for RNA and DNA synthesis and the cell proliferation were found to be markedly stimulated. The apparent uptake of leucine-3H was instead reduced in 2-day and, less still, in 7-day treated cells. In parallel with ultrastructural studies, these data suggest that ACTH orderly activates the template activity of chromatin while eliciting the differentiation and hypertrophy of human adrenocortical cells.

Interaction of gelatin with stereospecific binding proteins and its enhancement of competitive binding assays.

The effect of gelatin (0.5 g/l) on binding curves at high dilution of three classes of stereo-specific binding proteins was studied. These included two antibodies (to oestradiol and aldosterone), six transins (horse and dog transcortins, human thyroxine-binding globulin, human sex steroid-binding globulin, and guinea pig transprogestin), and one receptor (bovine adrenal protein kinase). Gelatin increased the apparent binding of all these proteins, particularly at the highest dilutions and sometimes in a striking manner. While much of this action can be attributed to its decreasing the adhesion of the dilute binding protein to glass, gelatin also increased the apparent uptake of some tracers by certain adsorbents. Similar findings were obtained using human gamma globulin (2 g/l). These effects resulted in increased sensitivity and improved reproducibility in the assays employing them.

The effects of various water-sample treatments on the apparent uptake of glutamic acid by natural marine microbial populations.

The apparent glutamate utilization by natural marine microbial populations was shown to be greatly influenced by the method used to terminate the uptake reaction. There was a significant difference in the amount of labeled material associated with the microorganisms when treated with either acid or buffered formaldehyde before the sample was assayed. A comparison of the data collected from acidified and nonacidified water samples resulted in significant differences in the following calculated values: percentage respired, the maximum velocity of uptake (Vmax), the turnover time (Tt), and the transport constant and natural substrate concentration (Kt + Sn). The rates of radioactivity incorporation into CO2 and acidified and nonacidified cells were followed with time and were found to be nonlinear after extended incubation.Data is presented which indicate that the labeled material that is released during acidification is that associated with the glutamate pool. The effects of these observations on the interpretation of data collected during heterotrophic potential studies are discussed.

Detection of the carrier of Wilson's disease

SUMMARYWhole-body counting over a three- to four-week period following the intravenous administration of copper 67 in 11 normal volunteers, 2 neurological control patients, 7 control subjects with cirrhosis, and 10 homozygotes and 7 heterozygotes of Wilson9s disease showed that whole-body retention of radio-copper was prolonged in the wilsonian subjects, both homozygous and heterozygous, and in cirrhotic patients with ascites or hepatocellular failure or both. If the latter can be excluded, prolonged whole-body retention of radiocopper serves to identify the presence of the abnormal gene or allele of Wilson9s disease. Because of overlap, it is not possible to distinguish the heterozygote from the homozygote by whole-body counting alone. External probe counting over the liver and muscle, carried out in 5 control subjects, 8 homozygotes, and 5 heterozygotes, revealed abnormal hepatic uptake with little apparent release of radiocopper and usually evident uptake in muscle in the homozygotes and reasonably normal hepatic uptake with delayed release and no apparent muscle uptake in the heterozygotes, compared with the control subjects. It appears that external monitoring of hepatic and muscle radioactivity, in addition to whole-body turnover measurements after intravenous copper 67, permits more accurate determination of the genetic status of individuals in respect to Wilson9s disease.

The influence of microbial contamination of fresh and washed beetroot disks on their capacity to absorb phosphate

When plant storage tissue is cut into thin disks it rapidly develops a high capacity to absorb phosphate from dilute solutions. The recent trend has been to attribute the development of this ability to the increased metabolic activity of bacteria known to be containing the tissue. Data presented in this paper shows that bacterial contamination of the tissue does contribute to the apparent uptake of phosphate by the disks. However, during the ageing process the number of bacteria decrease and therefore contribute less to the total uptake in the aged tissue. If the tissue is prepared and maintained in a sterile condition it is still able to develop a high capacity for phosphate absorption during ageing.

Uptake of organic material by aquatic invertebrates. VI. Role of epiflora in apparent uptake of glycine by marine crustaceans

Soft-bodied marine invertebrates from most invertebrate phyla are capable of taking up amino acids from seawater. Marine crustaceans were originally reported not to accumulate amino acids. Artemia salina, Limnoria tripunctata, Tigriopus californicus, and Corophium acherusicum were examined for their ability to accumulate C14-labelled glycine from dilute solution in seawater. In initial experiments with Artemia and Limnoria the organisms were found to become very radioactive. When animals were preincubated in streptomycin or in a mixture of antibiotics, uptake of the C14-glycine was drastically reduced. Microorganisms associated with the arthropods and in the culture media were found capable of accumulating C14-labelled glycine. Efforts to demonstrate removal of amino acids from seawater by colorimeteric determination of material remaining in the medium were unsuccessful. The microorganisms responsible for the uptake are apparently associated with the exoskeleton of the organisms and not the gut. There is probably no substantial contribution to the nutrition of these crustaceans by the epiflora. Preincubation in the antibiotic mixture depressed the uptake of C14-glucose and C14-acetate by about an order of magnitude. It is concluded that there is no evidence for accumulation or assimilation of small organic compounds by the small crustaceans examined.

Uptake and assimilation of amino acids by platymonas.

The marine flagellate Platymonas subcordiformis rapidly takes up amino acids at concentrations likely to be found in nature. The relation between velocity of uptake and substrate concentration was determined, and the apparent maximum uptake velocity estimated. Accumulated C14 amino acids were assimilated into alcohol-insoluble compounds and entered oxidative pathways as shown by detection of evolved C14O2. The contribution of the uptake mechanism at an ambient glycine concentration of 1.0 µmole/l. to nitrogen requirement of the cell was found to be roughly 10% for optimal laboratory growth conditions. In nature, where growth conditions are probably less favorable, the contribution would be considerably greater. This provides further support for a normal role of heterotrophy in phytoplankters.

Interdependent Fluxes of Amino Acids and Sodium Ion in the Pigeon Red Blood Cell

Abstract The Na+-dependent uptake of each of eight neutral amino acids by the pigeon red blood cell in vitro is associated with an increase in Na+ influx, whereas three neutral amino acids that have uptakes little affected by Na+ cause no significant stimulation of Na+ movements. No net uptake of Na+ is detectable during incubation with any of these amino acids, and stimulation of Na+ efflux, as well as influx, is seen directly during the uptake of glycine, alanine, and β-alanine. Neither the uptake of alanine nor the associated Na+ movements are inhibited by ouabain at a concentration sufficient to block the normal active extrusion of Na+ from the cell. The stimulation of Na+ influx by alanine and glycine occurs additively when both amino acids are present together. Analysis of the cellular concentrations of several neutral amino acids indicates that all the apparent uptake of glycine and alanine caused by Na+ can be accounted for in terms of homogeneous and heterogeneous exchange with analogous endogenous amino acids. The Na+-dependent increments of influx (Δvs) of glycine, alanine, and β-alanine parallel quantitatively the associated increases of Na+ influx (Δvna) over the concentration ranges tested, although the kinetics and the stoichiometry are different for each amino acid, the mean values of the ratio Δvna:Δvs being 1.53, 2.52, and 0.96, respectively. Possible interpretations of these findings are discussed.

Opsonic effect of frog yolk.

THERE is evidence that at least some yolk proteins of vertebrates originate in the liver and are transported to developing oocytes through the circulation, for example in the fish1, frog and chicken2. Marked pinocytotic activity during oocytic yolk accumulation has been noted in a variety of organisms and is probably related to protein uptake3. In view of the apparent ready uptake of yolk proteins by oocytes, we became interested in the responses of phagocytic cells of the reticuloendothelial system (RES) to frog yolk protein and found that yolk of Rana pipiens, labelled with fluorescein and solubilized with sodium chloride, is readily cleared from the blood of mice4. In addition, however, we noted that yolk injected intravenously also seemed to increase the rate of clearance of other materials. We have therefore investigated the opsonic effect of frog yolk.

Stimulation of respiration and inhibition of glycolysis in lobster axons by menadione and some related naphthoquinones

Lobster nerves metabolize glucose to a considerable extent via a direct oxidative pathway. The presence of 10 −5 M menadione strongly inhibits anaerobic glycolysis but greatly stimulates oxidative metabolism. Lobster nerves take up sugars from solution. Glucose is taken up readily and continuously for some time; sucrose and mannitol reach equilibrium at a low level and after a short period of time and are not taken up thereafter. Menadione markedly stimulates apparent uptake of glucose but has no effect on mannitol. This stimulation is due to the increased metabolism of glucose. Glucose uptake is also stimulated by removal of Ca ++ and Mg ++ from the medium.

Relative susceptibility to malathion contamination of six animal‐feed ingredients

AbstractMalathion uptake by six feed ingredients was investigated using stacks of small sack‐cloth covered units, simulating surface samples from full bags, sprayed with a dispersible powder formulation at a rate equivalent to about 165 mg./sq. ft.For units stored at 30° and 70% R.H., apparent uptake was about 10% of the initial deposit for citrus pulp, soya‐bean meal, cottonseed meal and groundnut meal, 30% for coconut meal and 50% for rice bran. These levels were reached after 5‐9 weeks' storage, and did not vary greatly over the period of study (1‐13 weeks post‐spraying) except in rice‐bran and coconut meal where the level increased markedly up to 9 weeks after spraying, but had decreased slightly by 13 weeks. No significant differences occurred between units stacked so as to simulate the under surface of a bag, and those simulating the upper surface. The differences in uptake between the various ingredients confirm the assumption that commodities with high oil‐content are likely to be most susceptible to contamination. Supplementary comparisons for citrus pulp and coconut meal showed that apparent uptake was greater at 30° than at 20°, but the effect of a slightly lower storage humidity (63%) was not significant.The practical significance of these results in relation to the use of malathion water‐dispersible powders for the control of insect infestation in bagged feed ingredients is discussed, and estimates of contamination likely to occur in full sacks are given.

Effect of a prolonged fast on the apparent galactose uptake of the isolated rat diaphragm in vitro.

Effect of a Prolonged Fast on the Apparent Galactose Uptake of the Isolated Rat Diaphragm in vitro