Rb86 Uptake Research Articles

Red and blue light-stimulated proton efflux by epidermal leaf cells of the Argenteum mutant ofPisum sativum

Light stimulates leaf expansion in dicotyledons by increasing apoplastic acidification, cell wall loosening and solute accumulation for turgor maintenance. Red and blue light enhance growth via different photosystems, but the cellular location and modes of action of these systems is not known. Here, the effect of red and blue light was studied on transport processes in epidermal cells of expanding leaves of the Argenteum mutant of Pisvm sativum. Both red and blue light caused extracellular acidification by isolated epidermal tissue, which was stimulated by extracellular K+ and inhibited by DCCD at 0.1 mol m(-3). Acidification induced by red compared with blue light showed different saturating kinetics in fluence rate-response curves. Under near saturating light conditions the effects of red and blue light were additive. The red light-induced acidification was inhibited by far-red light while the blue light-induced acidification was not. Light caused a hyperpolarization of the membrane potential in epidermal strips, and stimulated Rb-86(+) uptake by epidermal protoplasts. These results show that phytochrome and an additional blue light-photoreceptor function in isolated epidermal cells to promote proton efflux, hyperpolarization, and cation uptake.

The kinetics of vascular thermotolerance in SCK tumors of A/J mice

Development of thermotolerance has been observed in diverse biological systems. Despite the important role of blood circulation in heat-induced tissue damage, little is known about vascular thermotolerance. The kinetics of vascular thermotolerance in SCK tumors of A/J mice was investigated in this study. A single heating at 43.5°C or 44.5°C for 1 hr caused marked damage in tumor vasculature, as demonstrated by a marked decrease in Rb-86 uptake (% of injected dose/g of dried tissue). The tumor vasculature became resistant or tolerant to subsequent heatings at those temperatures when the tumors were preheated at 42.5°C for 1 hr. Vascular thermotolerance became significant at 5 hr and reached its maximum at 18 hr after preheating at 42.5°C. When the vascular thermotolerance was at its peak, heating at temperatures as high as 44.5°C for 1 hr could not reduce the tumor blood flow. The vascular thermotolerance decayed considerably but not completely at 72 hr after the preheating. The vascular thermotolerance may exert a profound implication on the response of tissues, including tumors, to multiple heatings.

Rubidium-86 uptake by red blood cells of breast cancer patients.

The red blood cell (RBC) uptake of rubidium-86 (Rb-86), a sensitive in vitro test of RBC membrane transport, was measured in 22 controls, 8 patients with benign breast lesions, and 30 stage I/II, 13 stage III/IV untreated breast cancers. Total Rb-86 transport was measured. Following ouabain block, passive transport was determined, allowing calculation of active Rb-86 uptake by difference. There was a significant decrease in total and passive uptake by RBCs from patients with breast cancer when compared to controls and those with benign lesions (total uptake 58.6 +/- 6.1% versus 63.6 +/- 3.9%, P less than 0.01; passive uptake 38.7 +/- 6.8% versus 42.7 +/- 4.6%, P less than 0.02). The Rb-86 uptake returned towards normal in successfully treated stages-II-to-IV patients. There were no correlations with the patient's age, hematocrit, or incubation hematocrit with RBC Rb-86 uptakes. Results from incubation in Krebs-Ringer solution were not consistent with a plasma blocking factor. The RBC potassium content was slightly increased in the cancer patients. This, along with decreased passive transport, eliminates the nonspecific malfunction of the Na-K-pump as an explanation, and suggests that the decreased uptake is a cancer-related phenomenon.

Modification of ultrasound induced changes in mammalian cells by increased viscosity of medium and increased ambient pressure.

Ehrlich ascites tumour cells (E.A.T.) in suspension were exposed to ultrasound of frequency 1x5 MHZ, intensities 1x4, 2x8 W/cm2 for 60 min at 37 degrees C. The suspensions of E.A.T. cells were contained in Perspex vessels with Melinex windows, situated in the near field of a piezoceramic transducer. Subsequently the rate of net influx of Rb-86 ions was studied over a period of 90 min. A reduced Rb-86 activity of insonated cell populations was observed compared to controls. Similar experiments were carried out involving E.A.T. cells suspended in isotonic medium containing 0x25 per cent agar (2x1 centipoise). No significant depression of uptake of Rb-86 ions was observed at 2x8 W/cm2, 1x5 MHZ. Cells insonated in normal medium at 1x9 atmos. helium pressure subsequently showed no depression of Rb-86 uptake, compared to controls, following insonation at 2x8 W/cm2, 1x5 MHZ for 60 min.

Rb86 uptake of various organs of the spontaneously hypertensive rats: (a preliminary note).

Twenty spontaneously hypertensive rats (SHR) and 20 control rats were used for measurements of Rb86 uptake of various organs. Hemodynamic measurements and the heart weight to body weight ratio showed a significant and sustained hypertension and increased heart rate in SHR; Ratio of Rb86 uptake in the kidney, brain, liver, adrenal gland, pancreas, and spleen to that in RV was smaller in SHR than that in the control rats. The ratio of Rb86 uptake of inner layer to outer layer of LV, which represents distribution of blood flow to the endocardial layer and epicardial layer, was not different between SHR and the control rats. The fraction of regional flow in the outer and inner cortex, juxtamedulla, and medulla of the kidney was not different between SHR and the control. The present preliminary study may suggest that myocardial blood flow in SHR is greater than that in the control rats. The relationship between cardiac hypertrophy and myocardial flow was discussed.

EFFECT OF HYPOXEMIA AND HYPERCAPNIA ON REGIONAL DISTRIBUTION OF MYOCARDIAL BLOOD FLOW.

The effect of hypoxia and hypercapnia on regional coronary blood flow and vascular resistance (CVR) was studied in dogs without thoracotomy. Gas tensions were varied by ventilation at controlled rates with gas mixtures containing 4–100% O2 and 0–24% CO2. After 10 min intravenous infusion of Rb86, the animals were killed and the heart isotope content determined. Blood flow to the left ventricle was calculated by the Fick principle from the isotope uptake and the mean difference in radioactivity of arterial and coronary sinus blood. Patterns of flow elsewhere were estimated from the rates of regional Rb86 clearance. Myocardial Rb86 clearance in the right and left ventricles has been previously shown to be closely related to the rate of coronary blood flow. Hypoxemia and severe hypercapnia (pCO2 above 100 mm Hg) both produced a profound fall in CVR. With hypoxemia this decrease was more marked in the right ventricle. Elevation of pCO2 exaggerated the normal difference in Rb86 uptake between inner and outer thirds of the wall of the left ventricle, while hypoxemia reversed the normal gradients. Hypercapnia did not affect these gradients in the right ventricle, but hypoxemia significantly reduced them.

Ion Uptake by Soybean Root Tissue Depleted of Calcium by Ethylenediaminetetraacetic Acid

Calcium has a fundamental role in the cellular processes of ion absorption and retention. The ion is generally credited with having beneficial effects on the semipermeability of membranes and structure of protoplasm (9,12). The electron microscope shows Ca deficiency to result in disorganization of membrane structure (19). In addition, the presence of calcium in solution was found by Viets (25) to increase the uptake of other ions, a phenomenon widely confirmed, but with variations in extent and conditions of response. Calcium is important in cation selectivity. The K/Na (or Rb/Na) absorption ratio increases in the presence of calcium (14,26), and the inhibitory effect of Na on K uptake is practically eliminated (7). The importance of calcium is sufficiently great in salt uptake studies that the root-to-solution ratio can affect K/Na absorption due to variable dissociation of calcium from the root tissue (15). In the presence of adequate calcium there is no initial exchange adsorption of the rubidium ion (8). Epstein (7, 8) notes that Ca in the solution around root tissue represents the normal physiological condition, and the ion is essential for the integrity of the selective ion transport mechanism. The selectivity is thought to reside in specific ion carriers. Jacobson et al. (13), on the other hand, conclude that the stimulation of K absorption by Ca results from blocking an interfering cation such as H or Li. Waisel (26) maintains that Ca increases the diffusion of K across the outer cell membrane, which he considers to be the rate-limiting step of metabolic accumulation. Tanada (23) has recently reiterated his suggestion that a ribonucleoprotein complex containing free -SH groups is involved in the Ca activation of Rb uptake by mung bean root tips. In an initial investigation of ribonucleoprotein as a carrier moiety, an EDTA-initiated degradation of RNA in soybean roots resulted in impaired respiration, ion accumulation, and ion retention (10). This result was attributed to removal of Ca and Mg by EDTA.3 However, treatment with EDTA in the cold, which would limit degradative metabolism, increased Rb88 uptake, a result similar to that reported by Tanada for ultraviolet treatment (20), ribonuclease treatment (21), sulfhydryl inhibition (22), and HCl or NaCl treatment (20). Rb86 uptake may be increased and P3204 uptake decreased by EDTA, citric acid, or alkaline phosphate pretreatment (20). We have now explored in some detail the effect of a short-term pretreatment with EDTA on ion uptake by soybean root tissue. Pretreatment removes much of the root Ca, and increases the subsequent metabolic uptake of Rb86-labeled K while decreasing that of phosphate. These effects are reversed by addition of Ca. Calcium removal appears to affect accumulation of the ions into the cytoplasm.

The Effect of Soil Moisture and Rubidium Concentration on Diffusion and Uptake of Rubidium‐86

AbstractAn autoradiographic technique was used to study the effect of soil moisture and Rb concentration on Rb86 diffusion and uptake by corn plants. Changes in soil moisture influenced the rate of diffusion, rate of root elongation, and the incidence of root hairs. The self‐diffusion of Rb86 was linearly correlated (R2 = 0.89) positively with soil mositure, Rb concentration, and interaction of these two factors.The correlation of Rb86 uptake from the soil was positively correlated with Rb86 diffusion values approximated from measurements made of the depleted areas about the roots. When the root diameter used in the calculation included the length of the root hairs, the r2 was 0.70 and when the root hairs were not included the r2 was 0.56. The correlation of uptake with the values of Dp/b from self‐diffusion studies gave an r2 of 0.99.Uptake by roots without root hairs was linearly correlated (r2 = 0.98) with soil moisture, Rb concentration, and their interaction. Since the uptake relationships were similar whether or not the roots possessed root hairs, it was concluded that moisture's effect on rate of diffusion was of greater significance in its effect on Rb86 uptake than was its effect on root hair incidence in these experiments.

Effect of thyrotropin on fractional blood flow of chick thyroid gland

The effect of thyrotropin (TSH) on the blood flow of the chick thyroid has been estimated by the distribution of Rb86. Mean thyroidal blood flow estimated from the 30-sec Rb86 uptake was 4.60% of cardiac output/g of tissue. During the 1st hr after the intracardiac administration of TSH, there was no effect on the thyroidal blood flow fraction; at 2 hr there was a significant response; by 4 hr the blood flow fraction had doubled. The response then gradually ebbed and disappeared by 24 hr. The long latency of the hyperemic response to TSH is interpreted as indicating that hyperemia is secondary to earlier metabolic activation. Of the various consequences of TSH action, only those with similarly long latencies, such as enhancement of iodide uptake, could possibly be dependent on the hyperemia. The thyroidal blood flow fraction remained constant during growth from 1.5 to 30 days of age, while the relative thyroid weight declined sharply. TSH produced its characteristic effect at all ages studied.

Clearance of Rb86 from Coronary Blood by the Atria of Dogs.

The rate of clearance of Rb86 from blood by several areas of the atria was studied in 18 dogs because of evidence that Rb86 uptake and rate of coronary blood flow are closely related. Mean rates of clearance averaged 0.40 ml blood/g/min. These were not significantly different in the right atrium, left atrium and interatrial septum. Rb86 uptake by the atria formed a larger portion of total myocardial uptake when cardiac output was low. Frequently the clearance per gram of tissue exceeded that found simultaneously in the ventricles. Finally, this indicates that atrial flow is better maintained when the animal is in poor condition than is flow to the ventricles.

Effect of Placement on the Absorption of Rb86 and P32 from Soil by Corn Roots

AbstractPlacement of Rb86 and P32 in the soil affected their relative uptake by corn roots. Autoradiographic techniques were used to determine the uptake processes involved. Banding of the fertilizer rather than mixing with the soil affected Rb86 uptake more than P32 uptake. The diffusion rate for Rb86 in the soil was much larger than for P32. Also, Rb86 was translocated more extensively throughout the corn root than was P32.The greater uptake of Rb86 from band applications appeared to be due to both a greater facility for uptake by a small portion of the root and a greater diffusion of Rb86 out of the band.

Determination of blood flow to the rat pituitary gland.

A radioactive tracer method, employing Rb86, is described for measurement of hypophyseal blood flow in the pentobarbitalized rat. The results indicate that the perfusion rate of the posterior lobe is 3.6 ml/gm/min. The anterior lobe has a minimal perfusion rate of 0.59 and a maximum of 0.90 ml/gm/min. under the experimental conditions employed. The time pattern of Rb86 uptake of both lobes of the pituitary is similar to that of non-nervous tissue, indicating that the blood-brain barrier does not extend into either part of this gland.

Differences in the rate of Rb86 uptake by several regions of the myocardium of control dogs and dogs receiving 1-norepinephrine or pitressin.

Differences in the rate of Rb86 uptake by several regions of the myocardium of control dogs and dogs receiving 1-norepinephrine or pitressin.