Uptake Of Radioactive Phosphate Research Articles

Uptake of inorganic phosphate by the maternal border of the guinea pig placenta.

Mechanism of uptake of inorganic phosphate (Pi) by the maternal border of the dually perfused guinea pig placenta was studied using the paired-tracer dilution technique with 32P-phosphate and 14C-sucrose being the tracers. Placental uptake of radioactive phosphate increased when the concentration of Pi in the perfusion fluid was reduced, and it decreased during anoxia, in presence of CN or during perfusion with low-Na or Na-free fluids. Iodoacetate was without effect. These observations are consistent with placental uptake of Pi being effected by a carrier mediated process dependent on external Na and, partly, on placental metabolism. Unidirectional flux of Pi from the maternal vascular space into the cell compartment of the placenta, estimated from the values of instantaneous extraction of 32P, correlated significantly with foetal weight. The flux per unit weight of the foetus was 17.0 +/- 1.0 nmol X min-1 g-1.

Lithium Effects on Magnesium, Calcium, and Phosphate Metabolism in Rats

Rats were treated with lithium chloride for 8 weeks. At the last day of lithium administration, the animals were given radioactive calcium, magnesium, and phosphate. Electrolyte content and radioactivity were determined in serum, bone, muscle, liver and brain. Lithium led to an increase of inorganic phosphate in muscle and a decrease in serum. Uptake of radioactive phosphate was increased in muscle and liver but reduced in bone. The amount of magnesium in muscle and serum was increased in the lithium-treated rats, whereas the uptake of radioactive magnesium into bone was decreased. Uptake of radioactive calcium into bone was reduced, and radioactive calcium in serum was increased after lithium.

Effects of growth hormone on tissue metabolism in broiler chicks.

1. The effect of bovine growth hormone (GH) on cartilage, liver, muscle, pancreas and spleen has been investigated. 2. Tissue RNA was elevated in the liver, muscle and spleen of the GH-treated chicks while uptake of radioactive phosphate into RNA was stimulated for both liver and spleen. 3. The GH-treated chicks had an increased cartilage protein content together with a higher rate of incorporation of 14C-methionine pancreatic protein.

THE MECHANISM OF ABSORPTION AND UTILIZATION OF PHOSPHATE BY BARLEY PLANTS IN RELATION TO SUBSEQUENT TRANSPORT TO THE SHOOT

SummaryAn attempt has been made to distinguish between the process of absorption of orthophosphate by the roots of whole barley plants and that of subsequent transport to the shoot. Such selection can be induced by treatment with growth regulators and inhibitors of specific biochemical stages in phosphorus metabolism. The presence of physiological concentrations of D‐mannose in the root environment has little effect on the overall uptake of radioactive phosphate. The metabolic fate of the absorbed phosphate is, however, severely affected and the ion appears to be reversibly sequestered in the form of hexose monophosphates other than those found to be labelled under normal conditions. Both glucose‐1 ‐phosphate and mannose‐6‐phosphate contain radioactive phosphorus after treatment with mannose. Although overall uptake is relatively unaffected, mannose specifically inhibits further transport of the metabolized phosphate to the shoot and it is concluded that this transport is directly dependent on the prior incorporation of the incoming phosphate into a specific sequence of organic compounds. The results are discussed in relation to the possible mechanisms involved in the separate processes of absorption and transport.

The effects of treatment with gonadotrophins or with oestrogen on the thyroid gland of the immature rat.

SUMMARY The uptake of 131I by the thyroid gland increased 72 hr. after the injection of pregnant mare serum gonadotrophin (PMS) into immature female rats whether ovulation occurred or not. PMS failed to produce this effect in male rats but oestrogen administration increased 131I uptake in both male and female immature rats, suggesting that oestrogen was responsible for the effect of PMS in females. Both PMS and oestrogen may increase the uptake of radioactive phosphate by the thyroid of female but not male rats; oestrogen may stimulate thyroid-stimulating hormone (TSH) secretion in immature female rats. These effects of oestrogen in the female made it impossible to determine whether the 'ovulatory surge' in luteinizing hormone secretion in PMS-treated rats was associated with an increased secretion of TSH or not.

The uptake of radioactive phosphate by yeast: II. The primary phosphorylation products

The first assimilation products of phosphorus in yeast cells have been investigated using radioactive orthophosphate as a tracer. It has been shown that one of the first steps of phosphate uptake consists in incorporation of phosphorus into ATP, GTP and (much more slowly) UTP. The ratio of the rates of incorporation of 32P into ATP and GTP is about 1: 0.4 at 1°.

The uptake of radioactive phosphate by yeast: I. The uptake of phosphate by yeast compared with that by higher plants

It has been shown that first step of active phosphate uptake by Saccharomuces cervisiae can be described by a Langmuir isotherm. Probably only one type of enzymic adsorption site is involved in this initial step. The affinity of orthophosphate ions for these groups is of the same order of magnitude as that found in plant roots by Van Den Honert.

THE EFFECT OF RHIZOPLANE FUNGI ON THE UPTAKE AND METABOLISM OF NUTRIENTS BY TOMATO PLANTS

The effects of infestation of the roots of tomato seedlings with naturally occurring rhizoplane fungi on the uptake of various nutrients has been studied. Fusarium sp. suppressed the uptake of radioactive phosphate, sulphate, bicarbonate, and glucose by the varieties Bonny Best and Geneva 11. Trichoderma viride Pers. suppressed the uptake of inorganic ions but increased the uptake of glucose in the varieties Moscow and Loran Blood. Marked differences were observed in the distribution of radioactivity among soluble compounds of the shoots of infested and noninfested plants after the supply of C14-labelled glucose or bicarbonate.Rhizoplane fungi appear to have a complex influence on the metabolic activities not only of the root but of the whole plant. This indicates the importance of being aware of the biological aspects of root environment in experimental studies with plants.

Studies on the uptake of radioactive phosphate in ovarian follicles of different size in the rabbit.

Studies on the uptake of radioactive phosphate in ovarian follicles of different size in the rabbit.

A note on the uptake of radioactive phosphate in the skeleton of rachitic rats.

A note on the uptake of radioactive phosphate in the skeleton of rachitic rats.

The effect of temperature upon the uptake of radioactive phosphate by human erythrocytes in vitro.

The effect of temperature upon the uptake of radioactive phosphate by human erythrocytes in vitro.

The uptake of radioactive phosphate by the excised gill of the mussel, Mytilus edulis.

The uptake of radioactive phosphate by the excised gill of the mussel, Mytilus edulis.